Department of Health and Human Services
OFFICE OF 
 
IN  SPECTOR GENERAL 
 
 
 
 
 
 
 
A E H :
DVERSE  VENTS IN  OSPITALS
 
N   I A
ATIONAL  NCIDENCE  MONG 
 
M B  
EDI  CARE  ENEFICIARIES
 
 
 
 
 
 
 
Daniel R. Levinson  
Inspector General 
 
November 2010 
OEI-06-09-00090 
         
 E X E C U T I V E   S U M M A R Y  
OBJECTIVES
 
To estimate the national incidence of adverse events for hospitalized 
Medicare beneficiaries, assess the preventability of such events, and 
estimate associated costs to Medicare.  
BACKGROUND 
The term adverse event describes harm to a patient as a result of 
medical care, such as infection associated with use of a catheter.  The 
term never events refers to a specific list of serious events, such as 
surgery on the wrong patient, that the National Quality Forum (NQF) 
deemed should never occur in a health care setting.  The Tax Relief 
and Health Care Act of 2006 mandates that the Office of Inspector 
General report to Congress regarding the incidence of never events 
among Medicare beneficiaries, the payment for services in connection 
with such events, and the Centers for Medicare & Medicaid Services 
(CMS) processes to identify events and deny payment.   
We selected a nationally representative random sample of 780 Medicare 
beneficiaries from all beneficiaries discharged during October 2008.  
Physician reviewers determined (1) whether an adverse event occurred, 
(2) whether the event was on the NQF list of Serious Reportable Events 
or the Medicare list of hospital-acquired conditions (HAC), (3) what the 
level of harm was to the patient, and (4) whether the event was 
preventable.  To establish an estimated adverse event incidence rate, we 
included events on the NQF and the HAC lists and events resulting in 
the most serious harm as defined by a patient harm index (prolonged 
hospital stay, permanent harm, life-sustaining intervention, or death).  
We also determined the cost to Medicare for hospital care resulting from 
the events.  Lastly, we identified additional events that resulted in 
temporary patient harm but were not comparable to the more serious 
events in our overall rate and assessed their preventability and cost. 
FINDINGS 
An estimated 13.5 percent of hospitalized Medicare beneficiaries 
experienced adverse events during their hospital stays.  Of the 
nearly 1 million Medicare beneficiaries discharged from hospitals in 
October 2008, about 1 in 7 experienced an adverse event that met at 
least 1 of our criteria (13.5 percent).  This rate projects to an estimated 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  i      
E X E C U T I V E   S U M M A R Y  
134,000 Medicare beneficiaries experiencing at least 1 adverse event in 
hospitals during the 1-month study period.  We calculated incidence 
rates for adverse events that met our three criteria:  0.6 percent of 
beneficiaries had an NQF Serious Reportable Event, 1.0 percent had a 
Medicare HAC event, and 13.1 percent experienced an adverse event 
resulting in the four most serious categories of patient harm.  An 
estimated 1.5 percent of Medicare beneficiaries experienced an event 
that contributed to their deaths, which projects to 15,000 patients in a 
single month.       
An additional 13.5 percent of Medicare beneficiaries experienced 
events during their hospital stays that resulted in temporary harm. 
Temporary harm events are those that require intervention but do not 
cause lasting harm.  Although many cases represent fairly minor 
occurrences, such as hypoglycemia, others were classified as temporary 
harm only because the patients were in the hospital for lengthy periods 
as a result of other, more serious, diagnoses, allowing hospitals enough 
time to address the harm prior to discharge.  Additionally, 28 percent of 
beneficiaries who experienced adverse events also had temporary harm 
events during the same stay.   
Physician reviewers determined that 44 percent of adverse and 
temporary harm events were clearly or likely preventable. 
Physicians determined that 44 percent of all events were preventable 
and 51 percent were not preventable.  (For the remaining 5 percent of 
events, physicians were unable to make determinations.)  Events 
related to surgery or procedures were less likely to be preventable than 
other types of events, such as hospital-acquired infections.  Preventable 
events were linked most commonly to medical errors, substandard care, 
and lack of patient monitoring and assessment.  Physician reviewers 
assessed events as not preventable when they occurred despite proper 
assessment and care or when the patients were highly susceptible to the 
events due to health status.  Nearly all events on the NQF and Medicare 
lists were assessed as preventable, a key criterion of both lists.   
Hospital care associated with adverse and temporary harm events 
cost Medicare an estimated $324 million in October 2008.   
Sixteen percent of sample beneficiaries in the Medicare Inpatient 
Prospective Payment System who experienced events incurred 
additional Medicare costs as a result.  The added costs equate to an 
estimated 3.5 percent of Medicares expenditure for inpatient care 
during October 2008.  To give these figures an annual context,             
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  ii  
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3.5 percent of the $137 billion Medicare inpatient expenditure for        
FY 2009 equates to $4.4 billion spent on care associated with events.  
Two-thirds of Medicare costs associated with events were the result of 
entire additional hospital stays necessitated by harm from the events.  
Additionally, these Medicare cost estimates do not include additional 
costs required for followup care after the sample hospitalizations.  
RECOMMENDATIONS 
As the Federal Governments principal agency for protecting the health 
of Americans, the Department of Health & Human Services (HHS) is 
uniquely positioned to lead national efforts to reduce adverse events in 
hospitals.  As part of a national strategy to improve health care quality 
mandated by the Patient Protection and Affordable Care Act (ACA), 
HHS is to identify areas that have the potential for improving health 
care quality.  Because many adverse events we identified were 
preventable, our study confirms the need and opportunity for hospitals 
to significantly reduce the incidence of events.  A number of agencies 
within HHS share responsibility for addressing this issue, most 
prominently the Agency for Healthcare Research and Quality (AHRQ) 
as a coordinating body for efforts to improve health care quality and 
CMS as an oversight entity and the Nations largest health care payer. 
Therefore, we recommend the following:  
AHRQ and CMS should broaden patient safety efforts to include 
all types of adverse events.  This broader definition would apply to 
a number of activities, including setting priorities for research, 
establishing guidelines for hospital reporting, developing prevention 
strategies, measuring health care quality, and determining payment 
policies. 
AHRQ and CMS should enhance efforts to identify adverse events.  
Identifying adverse events assists policymakers and researchers in 
directing resources to the areas of greatest need, setting clear goals for 
improvement, assessing the effectiveness of specific strategies, holding 
hospitals accountable, and gauging progress in reducing incidence. 
  AHRQ should sponsor periodic, ongoing measurement of the 
incidence of adverse events.   
  AHRQ should continue to encourage hospital participation with 
Patient Safety Organizations, entities intended to receive adverse 
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event reports from hospitals, and forward the information to a 
national AHRQ database.   
  CMS should use Present on Admission Indicators in billing data to 
calculate the frequency of adverse events occurring within hospitals.   
CMS should provide further incentives for hospitals to reduce the 
incidence of adverse events through its payment and oversight 
functions.  The ACA makes several changes to the HAC policy, 
including allowing the Secretary of HHS to expand the list of HACs.  
The ACA gives the HAC policy greater significance by using the list of 
HACs to implement Medicare payment penalties, create performance 
measures, and prohibit Medicaid payments for associated care.  The 
conditions of participation for Medicare and Medicaid require that 
hospitals have programs to demonstrate quality improvement where 
evidence shows practices can improve outcomes.   
  CMS should strengthen the Medicare HAC policy, such as by 
expanding the policy to include more events that harm beneficiaries.   
  CMS should look for opportunities to hold hospitals accountable for 
adoption of evidence-based practice guidelines.   
AGENCY COMMENTS 
We received comments on the draft report from AHRQ and CMS.   
AHRQ concurred with our recommendations, stating that adverse 
events affect hospital patients at an alarming rate and that it must 
continue working to improve patient safety.  AHRQ stated that it 
intends to foster continued improvement in both identifying and 
reducing adverse events through operational programs, research efforts, 
and further collaboration with other agencies.  CMS also concurred with 
our recommendations, stating that it is committed to the reduction of 
adverse events in hospitals and other health care settings and that 
although it has taken significant steps to address these issues, more 
work needs to be done.  CMS stated that it will aggressively pursue 
broadening the scope and definition of patient safety efforts to be more 
inclusive of various types of adverse events and more closely monitor 
and address hospital quality of care.  CMS also outlined several current 
and planned efforts to both create incentives and provide support for 
patient safety improvements by hospitals.  
 We made minor changes to the report based on technical comments.  
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 T A B L E   O F   C O N T E N T S  
EXE  C   UTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
 
 
 
I N T RO DUC T IO N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 
 
F I N D IN G S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 
An estimated 13.5 percent of hospitalized Medicare beneficiaries 
experienced adverse events during their hospital stays. . . . . . . . . . . . . 15 
An additional 13.5 percent of Medicare beneficiaries experienced         
events during their hospital stays that resulted in temporary harm . . . 20 
Physician reviewers determined that 44 percent of adverse events           
and temporary harm events were clearly or likely preventable. . . . . . . 22 
Hospital care associated with adverse events and temporary harm      
events cost Medicare an estimated $324 million in October 2008 . . . . . 27 
 
R E C O MMEN D A T ION S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 
  Agency Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 
 
APPENDIXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 
  A:  Tax Relief and Health Care Act of 2006 . . . . . . . . . . . . . . . . . . . . . . 35 
  B:  National Quality Forum Serious Reportable Events . . . . . . . . . . . . 37 
C:  Medicare Hospital-Acquired Conditions . . . . . . . . . . . . . . . . . . . . . . 38 
D:  Glossary of Selected Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 
E:  Methodology for Identifying Events and Determining         
Preventability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 
F:  Estimates, Confidence Intervals, and Key Statistics . . . . . . . . . . . . 46 
G:  Rates of Adverse Events and Temporary Harm Events by             
Patient Days  and Hospital Admissions . . . . . . . . . . . . . . . . . . . . . . 50 
H:  Adverse Events and Temporary Harm Events. . . . . . . . . . . . . . . . . 51 
I:   Agency Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 
 
A C K NO WL E D G M E N T S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 
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 I N T R O D U C T I O N  
OBJECTIVES 
To estimate the national incidence of adverse events for hospitalized 
Medicare beneficiaries, assess the preventability of such events, and 
estimate associated costs to Medicare.  
BACKGROUND 
Statutory Mandate and Office of Inspector General Response 
The Tax Relief and Health Care Act of 2006 (the Act) requires that the 
Office of Inspector General (OIG) report to Congress regarding the 
incidence of never events among Medicare beneficiaries; the extent to 
which the Medicare program paid, denied payment, or recouped 
payment for services furnished in connection with such events; and the 
processes that the Centers for Medicare & Medicaid Services (CMS) 
uses to identify such events and deny or recoup payment.1  OIG is also 
to make recommendations for such legislation and administrative action 
as OIG determines is appropriate.  (For relevant text of the Act, see 
Appendix A.)  To meet the requirements of the Act, OIG released a 
series of reports beginning in 2008 and will publish additional reports 
based on ongoing work.2   
Adverse Events in Hospitals 
Following a review of Medicare policies and expenditures, as well as 
consultation with CMS and the Agency for Healthcare Research and 
Quality (AHRQ), we chose to focus our work on inpatient acute care 
hospitals.  For fiscal year (FY) 2009, Medicare costs for inpatient care 
were $137 billion, constituting 28 percent of total expenditures.3  As a 
condition of participation in the Medicare and Medicaid programs, 
Federal regulations require that hospitals develop and maintain Quality 
Assessment and Performance Improvement (QAPI) Programs.4  As a 
 
1 Tax Relief and Health Care Act of 2006, P.L. 109-432  203. 
2 The studies in the series published to date are:  Adverse Events in Hospitals:  Overview of 
Key Issues, OEI-06-07-00470; Adverse Events in Hospitals:  State Reporting Systems,       
OEI-06-07-00471; and Adverse Events in Hospitals:  Case Study of Incidence Among Medicare 
Beneficiaries in Two Counties, OEI-06-08-00220, all published in December 2008; Adverse 
Events in Hospitals:  Public Disclosure of Information About Events, OEI-06-09-00360, 
January 2010; and Adverse Events in Hospitals:  Methods for Identifying Events,               
OEI-06-08-00221, March 2010.  
3 CMS, 2009 CMS Statistics Book, Table III.6, Office of Research, Development, and 
Information, CMS Pub. No. 03497, December 2009, p. 30.    
4 42 CFR  481.21.  
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part of their QAPI programs, hospitals must track medical errors and 
adverse patient events, analyze their causes, and implement preventive 
actions.5  Federal regulations do not require specific program 
characteristics.  The QAPI provisions also require that hospitals 
establish programs to demonstrate improvement in quality indicators 
for which there is evidence that practices will improve outcomes.6  As an 
additional quality effort, Quality Improvement Organizations (QIO) 
contract with CMS to assist hospitals in improving the quality of care 
for Medicare beneficiaries, including addressing patient safety issues.7   
A variety of terms, lists, and definitions are used to identify health care 
events that result in patient harm.  For purposes of the Act, the term 
never event means an event that is listed and endorsed as a serious 
reportable event by the National Quality Forum (NQF)8 as of   
November 16, 2006.9  The NQF uses the term serious reportable 
events to describe a specific list of events associated primarily with 
patient death or serious disability that are both egregious and 
preventable, concluding that they should never occur in a health care 
setting.  These became known as never events.  (For a list of NQF 
Serious Reportable Events, see Appendix B.)  The NQF list is often used 
by patient advocates and health care payers in establishing patient 
safety policies.10  The health care community now uses the term 
adverse event more commonly than never event to refer to harm 
experienced by a patient as a result of medical care.  After consulting 
with congressional committee staff in 2007, we expanded our approach 
to be consistent with patient safety research and industry trends.   
As used in this study, an adverse event is defined as harm to a patient 
as a result of medical care or in a health care setting.  Although an 
adverse event indicates that the care resulted in an undesirable clinical 
 
5 42 CFR  482.21(c)(2). 
6 42 CFR  482.21(a)(1). 
7 CMS, QIO Overview, last modified January 2010.  Accessed at 
http://www.cms.hhs.gov/QualityImprovementOrgs/ on September 29, 2010. 
8 NQF is a public-private membership organization created to develop and implement a 
national strategy for health care quality measurement and reporting.   
9 The Act,  203(d).  The NQF list is available online at http://www.qualityforum.org.  
10 As an example, The Leapfrog Group, a national nonprofit focused on patient safety 
issues, encourages hospitals to adopt policies to address Serious Reportable Events.  Leapfrog 
Group Position Statement on Never Events, updated November 11, 2009.  Accessed at 
http://www.leapfroggroup.org/for_hospitals/leapfrog_hospital_survey_copy/never_events on 
September 29, 2010. 
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outcome and may involve medical errors, adverse events do not always 
involve errors, negligence, or poor quality of care and are not always 
preventable.11  Research and policy to improve patient safety and 
reduce the incidence of adverse events often focus on identifying and 
addressing systemic problems that may lead to patient harm and avoid 
labeling the event as an outcome of negligence or poor quality.  
Additionally, researchers, policymakers, and health care entities 
sometimes adopt different standards for distinguishing between degrees 
of patient harm in determining whether they classify an occurrence as 
an adverse event.  Thus, entities tracking events may find different 
results depending on the list used to identify and classify events. 
The National Coordinating Council for Medication Errors Reporting and 
Prevention (NCC MERP) Index for Categorizing Errors can be used to 
classify adverse events by level of patient harm.  The NCC MERP Index 
was initially developed to categorize the effect of medication errors and 
considers whether the occurrences had an effect on the patients and, if 
so, how harmful they were.  The index includes categories for 
circumstances or occurrences that presented a risk but did not cause 
harm, often referred to as near misses, and those that caused harm.  
Table 1 shows the NCC MERP Index for Categorizing Errors. 
Table 1:  The NCC MERP Index for Categorizing Errors 
Level  Description  Event 
A  Circumstances or events occurred that had the capacity to cause error.   
Harm 
B  Error occurred but did not reach the patient. 
does not 
C  Error occurred that reached the patient but did not cause patient harm.  reach 
patient 
Error occurred that reached the patient and required monitoring to 
D 
preclude harm or confirm that it caused no harm. 
Error occurred that may have contributed to or resulted in temporary 
E 
harm and required intervention. 
Error occurred that may have contributed to or resulted in harm and 
F  required an initial or prolonged hospital stay.  Harm 
reaches 
G  Error occurred that contributed to or resulted in permanent patient harm. 
patient 
H  Error occurred that required intervention to sustain the patients life. 
I  Error occurred that may have contributed to or resulted in patient death. 
Source:  NCC MERP Index for Categorizing Errors, Press Release, Medication Errors Council Revises and 
Expands Index for Categorizing Errors:  Definitions of Medication Errors Broadened, June 12, 2001. 
 
11 R.M. Wachter, Understanding Patient Safety, McGraw-Hill, 2008. 
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Researchers have used the NCC MERP index for measuring and 
distinguishing other types of adverse events, rather than only 
medication errors.  For example, the Institute for Healthcare 
Improvement (IHI), a nonprofit organization that advises hospitals 
regarding health care quality, uses a modified version of the             
NCC MERP index to measure the degree of patient harm, regardless of 
whether the harm was the result of an error.12   
Present on Admission Indicators and Medicares Hospital-Acquired 
Conditions Policy 
Medicare reimbursement to acute care hospitals through the Inpatient 
Prospective Payment System (IPPS) is generally determined by 
grouping codes representing patient conditions into Diagnosis-Related 
Groups (DRG) based on the average cost of care for patients with 
similar conditions.13  Hospitals may submit Medicare claims under 
IPPS using nine diagnosis codes and six procedure codes for each 
hospital stay.  Historically, if a Medicare beneficiary experienced an 
adverse event that resulted in assignment of a more costly DRG, CMS 
paid the higher DRG.14   
Beginning October 1, 2007, hospitals are required to assign a Present on 
Admission (POA) Indicator to each principal and secondary diagnosis 
for acute IPPS claims for all discharges.15  This was an initial step in 
complying with the Deficit Reduction Act of 2005 (DRA), which required 
CMS to select at least two hospital-acquired conditions (HAC) for which 
hospitals would not be paid higher Medicare reimbursement.16   
 
12 F.A. Griffin and R.K. Resar, IHI Global Trigger Tool for Measuring Adverse Events, 
Institute for Healthcare Improvement Innovation Series 2007, pp. 45.    
13 CMS, Acute Inpatient PPS Overview, last modified Feb. 22, 2010.  The ICD-9-CM system 
assigns diagnoses and procedure codes associated with hospital stays and is maintained 
jointly by CMS and the National Center for Health Statistics.  Accessed at 
http://www.cms.gov/AcuteInpatientPPS/01_overview.asp on September 29, 2010. 
14 CMS, Press Release, Eliminating Serious, Preventable, and Costly Medical Errors  
Never Events, May 18, 2006.   
15 CMS, CMS Manual System, Change Request 5679 (July 20, 2007).  To effectuate the use 
of POA indicators, the FY 2008 IPPS rule implemented a more specific list of DRGs called 
Medicare Severity Diagnosis-Related Groups (MS-DRG).  MS-DRGs split some of the prior 
DRGs into two or three classes based on the presence of a complication or comorbidity.          
FY 2008 IPPS Final Rule, 72 Fed. Reg. 47130, 47138 (Aug. 22, 2007). 
16 DRA, P.L. 109-171  5001(c)(1), Social Security Act (SSA),  1886(d)(4)(D),                                  
42 U.S.C.  1395ww(d)(4)(D). 
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In response, CMS issued regulations outlining a policy to deny hospitals 
higher payment for hospital admissions complicated by any of              
10 categories of HACs.17  The DRA required that the conditions meet 
the following criteria:   
  conditions that are high cost, high volume, or both; 
  conditions that, when present as a secondary diagnosis, result in 
assignment of a case to a DRG that has a higher payment; 
  conditions that could be reasonably prevented by using readily 
available evidence-based guidelines; and  
  conditions that are identifiable based on one or more unique 
diagnosis codes.18   
Effective October 1, 2008, CMS began denying hospitals higher payment 
for care associated with these conditions.19  Examples of HACs include 
catheter-associated urinary tract infections and patient injury because 
of a fall.  For the full list of Medicare HACs, see Appendix C. 
Determining the Incidence of Adverse Events  
Research indicates that identifying adverse events retrospectively is a 
complex and difficult task, requiring extensive clinical knowledge, 
adequate documentation, and subjectivity on the part of the 
researcher.20  Medical records review is often considered the most 
definitive method for detecting adverse events because it can provide 
detail about both the adverse event and the circumstances, such as the 
patients condition prior to and following the event.21  However, medical 
records reviews can be costly, requiring hospital staff to make records 
available and substantial effort by physicians or other clinicians to 
review them.  To limit physician medical records reviews required to 
identify adverse events, cases can be screened to identify potential 
 
17 FY 2008 IPPS Final Rule, 72 Fed. Reg. 47130, 47202 (Aug. 22, 2007); and FY 2009 IPPS 
Final Rule, 73 Fed. Reg. 48434, 4847148491 (Aug. 19, 2008). 
18 SSA,  1886(d)(4)(D)(iv). 
19 FY 2009 IPPS Final Rule, 73 Fed. Reg. 48434, 4847148472 (Aug. 19, 2008); CMS, CMS 
Manual System, Change Request 6189 (Oct. 3, 2008). 
20 E.J. Thomas and L.A. Peterson, Measuring Errors and Adverse Events in Health Care, 
Journal of General Internal Medicine, 18(1), 2003, pp. 6167. 
21 E.J. Thomas, D.M. Studdert, and T.A. Brennan, The Reliability of Medical Record 
Review for Estimating Adverse Event Rates, Annals of Internal Medicine, 136(11), June 2002, 
pp. 812816.     
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adverse events using other methods, such as nurse reviews of medical 
records and analysis of POA indicators in hospital claims data. 
Nurse review of medical records.  Medical records screening can identify 
potential adverse events based on information in the medical records.  
The IHI Global Trigger Tool (GTT) uses a review of medical records to 
identify triggers that could signal patient harm, thereby identifying 
potential adverse events.  A trigger could be a description of the harm 
itself or a reference that indicates harm occurred (such as a return to 
surgery).  The review is designed to be completed by nurse reviewers, 
with the results then confirmed or refuted by a physician.  Barriers to 
medical records screening include incomplete records and high labor 
costs for review.    
Analysis of POA indicators.  Automated computer programs can review 
Medicare billing data, specifically the POA indicator codes assigned to 
each diagnosis, to identify conditions that developed during hospital 
stays and possibly constitute adverse events.  Although these programs 
enable examination of large numbers of hospital stays, barriers exist to 
POA analysis, including inaccurate or incomplete data.  CMSs POA 
coding requirement began in October 2007, and the accuracy and 
completeness of hospital coding of POA indicators have not yet been 
validated.  Additionally, conditions can be acquired in hospitals that are 
not related to medical care and therefore not adverse events.  
OIG case study.  Prior to this study, we conducted a case study of the 
incidence of adverse events occurring during October 2008 for a random 
sample of 278 Medicare beneficiaries hospital stays in 2 counties.22  We 
estimated that 15 percent of Medicare beneficiaries in the two counties 
experienced events meeting at least one of the following criteria:  events 
on the NQF list of Serious Reportable Events; events on Medicares list 
of HACs; or events involving prolonged hospital stays, permanent harm, 
life-sustaining intervention, or death (classified as F-I level of harm on 
the NCC MERP index).  An additional 15 percent of beneficiaries 
experienced events involving temporary harm (classified as E level of 
harm on the NCC MERP index).  The case study served in part to test 
the usefulness of various methods for identifying adverse events.  We 
found that, combined, nurse screening of medical records and analysis 
 
22 OIG, Adverse Events in Hospitals:  Case Study of Incidence Among Medicare 
Beneficiaries, OEI-06-08-00220, December 2008. 
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of POA indicator codes in billing data identified 94 percent of 
occurrences that physicians ultimately determined to be adverse or 
temporary harm events.23 
Determining the Preventability of Adverse Events  
To provide additional context regarding adverse events, some 
researchers have assessed whether adverse events were preventable 
and described the circumstances associated with events.    A 2008 
review of eight preventability studies found that the median percentage 
of adverse events judged preventable was 43.5 percent.24  Assessing 
preventability can provide greater understanding of the causes of 
adverse events, which can be used to develop actionable solutions to the 
systemic problems that lead to events.  Also, preventability is a 
statutory criterion of Medicares nonpayment policy for HACs; CMS was 
required to select only conditions that can be reasonably prevented by 
using readily available evidence-based guidelines.25 
Reducing the Incidence of Adverse Events 
Reducing the incidence of adverse events in hospitals is a critical 
component of efforts to improve patient safety and quality care.  The 
Institute of Medicine (IOM) report, To Err Is Human:  Building a Safer 
Health System, focused widespread attention on the problem of adverse 
events.  IOM cited two studies that used medical records reviews to 
identify adverse events and assess whether events were preventable.  
IOM concluded that preventable adverse events caused at least    
44,000 and perhaps as many as 98,000 deaths in hospitals each year 
and outlined a national plan to address adverse events.26   
As part of its plan, IOM recommended the creation of a nationwide 
system for the collection of standardized adverse event data by State 
governments.  As reported by OIG, 25 States and the District of 
Columbia had adverse event reporting systems in 2008, 11 of which 
 
23 OIG, Adverse Events in Hospitals:  Methods for Identifying Events, OEI-06-08-00221, 
March 2010. 
24 E.N. De Vries, M.A. Ramrattan, et al., The Incidence and Nature of In-Hospital Adverse 
Events:  A Systematic Review, British Medical Journal  Quality and Safety in Health Care, 
17(3): 21623, June 2008. 
25 SSA,  1886(d)(4)(D)(iv), 42 CFR  412.10; FY 2008 IPPS Final Rule, 72 Fed. Reg. 47130, 
47202 (Aug. 22, 2007).      
26 L.T. Kohn, J.M. Corrigan, and M.S. Donaldson, eds., To Err Is Human:  Building a Safer 
Health System, A Report of the Committee on Quality of Health Care in America, p. 102,  
IOM, National Academy Press, 2000.  
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  7  
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used the NQF list of Serious Reportable Events or a modified version of 
the list to define what events are reportable.27  To date, no national 
adverse event reporting system exists and there are no Federal 
standards regarding State systems.      
Following the IOM report, the Federal Government formed the Center 
for Quality Improvement and Patient Safety (CQuIPS) within AHRQ to 
provide national leadership in improving patient safety.  In a 2009 
report, AHRQ identified its core agency objectives for CQuIPS as 
developing a solid evidence base, designing useful tools for providers, 
and disseminating information for implementation.28  As mandated by 
Congress, AHRQ releases an annual report to the Nation about health 
care quality that is produced by CQuIPS and includes measures of 
patient safety.29  The National Healthcare Quality Report includes 
measures of the incidence of certain types of adverse events, using data 
from sources such as the Medicare Patient Safety Monitoring System 
(MPSMS), an AHRQ-CMS collaborative effort to identify adverse events 
through analyses of medical records and Medicare claims data for 
beneficiaries hospital stays.30  AHRQ is also responsible for 
implementation and oversight of the certification process for Patient 
Safety Organizations (PSO) created by the Patient Safety Act and 
Quality Improvement Act of 2005.31  PSOs are in the early stages of 
development, but are intended to receive adverse event reports from 
hospitals and forward the information to a national AHRQ database 
from which CQuIPS will analyze aggregated data.  AHRQ developed a 
set of event definitions and reporting tools known as the Common 
Formats, which PSOs can choose to use and which contain data 
elements that AHRQ determined are important for a complete and 
 
27 OIG, Adverse Events in Hospitals:  State Reporting Systems, OEI-06-07-00471, 
December 2008. 
28 AHRQ, Advancing Patient Safety:  A Decade of Evidence, Design, and Implementation, 
AHRQ Publication No. 09(10)-0084, November 2009.  Accessed at 
http://www.ahrq.gov/qual/advptsafety.htm on September 29, 2010.   
29 Healthcare Research and Quality Act of 1999, P.L. 106-129  2(a); Public Health Service 
Act (PHSA),  913, 42 U.S.C.  299b-2. 
30 D.R. Hunt, N. Verzier, et al., Fundamentals of Medicare Patient Safety Surveillance: 
Intent, Relevance, and Transparency, Advances in Patient Safety, 2005, p. 105.  Accessed at 
www.ahrq.gov/downloads/pub/advances/vol2/Hunt.pdf on September 29, 2010.    
31 The Secretary of Health and Human Services (Secretary) delegated authority to AHRQ to 
make these determinations, as well as to fulfill other requirements of the Patient Safety Act.  
Patient Safety and Quality Improvement Act of 2005, P.L. 109-41  2, PHSA,  924,                
42 U.S.C.  299b-24; 73 Fed. Reg. 70732 (Nov. 21, 2008).   
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useful adverse event report.32  A variety of organizations are eligible to 
become PSOs, including hospital associations, hospital chains, and 
patient safety consulting groups.33  For a 2009 OIG study, staff from 
selected PSOs reported barriers that could limit hospital participation 
in PSOs and questioned the usefulness of submitting data for 
aggregation.34  Finally, the American Recovery and Reinvestment Act of 
2009 appropriated $300 million to AHRQ to sponsor and disseminate 
research that compares the effectiveness of clinical care options, the 
purpose of which is to promote evidence-based medical care.35    
In March 2010, Congress passed health care reform legislation in the 
form of the Patient Protection and Affordable Care Act (ACA).36  The 
ACA includes a number of provisions to take effect over multiple years, 
including expanded funding and authority to the Department of Health 
and Human Services (HHS) to address health care quality issues.  
Among the initial efforts to implement the ACA, the Secretary is to 
establish a national strategy for quality improvement in health care by 
January 1, 2011.37  The law requires that the strategy address eight 
national priority areas, one of which is to improve patient safety.38  It 
also increases funding to CQuIPS for research grants to explore best 
practices.39  Among its payment provisions, the ACA expands the 
Medicare HAC policy to mandate hospital payment penalties for high 
rates of HACs,40 create new quality measures,41 and require State 
Medicaid agencies to deny higher reimbursement for care associated 
with HACs.42   
 
32 AHRQ, Common Formats for Patient Safety Data Collection and Event Reporting, Notice 
of Availability:  Common Formats Version 1.0, September 2, 2009.  Accessed at 
http://www.pso.ahrq.gov/formats/commonfmtv1_0fr.htm on October 12, 2010. 
33 PHSA,  924(b), 42 U.S.C.  299b-24(b). 
34 OIG, Adverse Events in Hospitals:  Public Disclosure of Information About Events,             
OEI-06-09-00360, January 2010. 
35 American Recovery and Reinvestment Act of 2009, P.L. 111-5, Division A, Title VIII. 
36 ACA, P.L. 111-148, was signed into law on March 23, 2010, after we had completed data 
collection and analysis for this study. 
37 P.L. 111-148  3011, PHSA,  399HH, 42 U.S.C.  280j.  
38 P.L. 111-148  3011, PHSA,  399HH(a)(2)(B)(vii), 42 U.S.C.  280j(a)(2)(B)(vii). 
39 P.L. 111-148  3501, PHSA,  933 and 934. 
40 P.L. 111-148  3008(a), SSA,  1886(p), 42 U.S.C.  1395ww(p). 
41 P.L. 111-148  3013 inserted new section 931 of the PHSA, 42 U.S.C.  299b-31, and 
added section 1890A(e) of the SSA, 42 U.S.C.  1395aaa-1(e). 
42 P.L. 111-148  2702. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  9  
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METHODOLOGY 
Scope 
This report estimates the national incidence of adverse events based on 
a representative sample of Medicare beneficiaries discharged from 
inpatient acute care hospitals during October 2008.  Our results are 
projectable to all Medicare beneficiaries hospitalized during this period 
nationwide.  To determine the estimated rate of adverse events, we used 
criteria developed by NQF, CMS, and NCC MERP.  We included in the 
estimated national incidence rate all patient harm that occurred during 
the hospital stay, regardless of whether it was preventable.  Also, the 
report provides a physician assessment of the extent to which identified 
events were preventable and analysis of billing data to estimate the cost 
to the Medicare program for increased reimbursement resulting from all 
events and preventable events. 
Sample Selection 
We selected a sample of Medicare beneficiaries from the National 
Claims History (NCH).  Of the 999,645 beneficiaries discharged from 
acute care hospitals during October 2008, we selected a random sample 
of 785 beneficiaries.  We excluded 5 beneficiaries as ineligible because 
the hospital was currently under OIG investigation, resulting in a 
sample of 780 beneficiaries.  In JulyOctober 2009, we requested and 
received medical records from hospitals regarding sample beneficiaries 
hospital stays.  Fifty-four of the beneficiaries had more than 1 hospital 
stay during October (50 had 2 stays and 4 had 3 stays).  Combined, 
sample beneficiaries had 838 hospital stays with discharges in  
October 2008 and an average length of stay of 5.2 days.43   
Identifying Adverse Events and Determining Preventability 
We conducted a two-stage review to identify adverse events experienced 
by each beneficiary.  The first stage used three screening methods to 
identify cases likely to include an event.  This enabled us to reduce the 
number of cases requiring the second-stage physician review.  During 
the first stage, we identified cases that met one or more of the following 
conditions:  (1) certified medical coders identified codes in the Medicare 
claims data that were listed as not present on admission, (2) nurse 
reviewers found evidence of a potential adverse event in the medical 
 
43 The average length of stay for hospitalized Medicare beneficiaries overall in 2007 was  
5.6 days.  CMS, 2009 CMS Statistics, Table IV.1 Medicare Short-stay Hospital Utilization, 
2009, Tab 1.   
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records, or (3) the beneficiary had a hospital admission within 30 days 
after discharge for his or her last sample hospital stay ending in 
October 2008.44   
We identified 420 cases for the second stage of review, which entailed a 
review of the full medical records by physicians to identify events.  To 
ensure consistency across physician reviewers, we facilitated weekly 
conference calls during which all physician reviewers discussed cases 
that either were complex or had possible implications for other cases.  
We included events experienced by patients during hospital stays or 
during prior, contiguous outpatient visits (wherein patients were 
transferred directly from outpatient care to inpatient care within the 
same facility).  For example, we included in our count an adverse event 
that occurred in a hospital emergency department immediately 
preceding admission to inpatient care.  We did not include events that 
occurred prior to a beneficiarys arrival on the hospital campus.  When 
an initial event caused a series of related events for the same patient, 
we collapsed the events into a cascade event, which counted as a 
single event.45  For a glossary of selected clinical terms used to describe 
events, see Appendix D. 
As part of the structured protocol, physician reviewers also determined 
the extent to which the identified events were preventable.  Generally 
speaking, physicians assessed events as preventable when they 
determined that harm could have been avoided through improved 
assessments or alternative actions.  Physicians assessed an event as not 
preventable when they determined that harm could not have been 
avoided given the complexity of the patients condition or the care 
required.  The physician protocol used the following response scale for 
assessing the preventability of events:  clearly preventable, likely 
preventable, clearly not preventable, likely not preventable, and unable 
to determine.  Physicians used their clinical experience and judgment to 
make preventability determinations.  They considered all evidence in 
 
44 We reviewed records for admissions that occurred within 30 days of the last beneficiary 
discharge.  Therefore, the 30-day window for reviewing readmissions did not span a fixed 
timeframe but began on the unique final discharge date for each beneficiary with the last 
possible admission occurring on November 30, 2008 (30 days following the final possible 
October 31, 2008, discharge).        
45 Based on OIG interviews with IHI staff, IHI defines a cascade event as one in which an 
initial event causes a series of related events for the same patient and advocates collapsing 
these into a single event.    
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the medical records, including the actions of hospital and medical staff 
and the patients condition.  Assessing an event as clearly preventable 
or clearly not preventable required a greater degree of certainty on the 
part of the reviewer.  For detailed information about the methodology 
for identifying events and determining preventability, see Appendix E.   
Data Analysis 
We performed analysis and generated estimates about adverse events 
for three categories:  incidence of events, preventability of events, and 
Medicare cost associated with events.  We also calculated separate 
estimates regarding these categories for temporary harm events.  For 
estimates and corresponding 95-percent confidence intervals for all 
statistical analyses, see Appendix F. 
Adverse event incidence analysis.  We calculated the estimated national 
adverse event incidence rate as the percentage of Medicare beneficiaries 
with at least one adverse event.  We defined adverse events as events 
that met at least one of the following criteria:   
1.  the event was on the NQF list of Serious Reportable Events, as the 
Act mandates; 
2.  the event was on Medicares list of HACs for which it denies higher 
payment; or 
3.  the event resulted in one of the four most serious categories on the 
NCC MERP index (classified on the index as F-I):   
- prolonged hospital stay, 
- permanent harm, 
- life-sustaining intervention, or  
- death.  
We also calculated individual rates for adverse events on the NQF list, 
the Medicare HAC list, and events classified as F-I on the NCC MERP 
index.  The overall adverse event incidence rate does not include events 
that physician reviewers identified as temporary harm events, defined 
as events that required intervention but did not cause lasting harm 
(classified as E level harm on the NCC MERP index).  We excluded 
these temporary harm events from our overall rate because we 
determined, in consultation with physician reviewers, that the effect of 
these events was not comparable to the more serious events meeting the 
three criteria.  We calculated a separate incidence rate for beneficiaries 
who experienced only temporary harm events.  We projected incidence 
rates to the population of Medicare beneficiaries discharged from 
inpatient acute care hospital stays during October 2008.     
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  12  
I N T R O D U C T I O N  
As an additional measure of adverse event rates, we calculated 2 ratios 
of adverse event incidence density:  events per 1,000 patient days and 
events per 100 hospital admissions.  These measures are commonly 
used by hospitals and medical researchers.46  For the resulting metrics 
and an explanation of the calculation method, see Appendix G. 
Preventability analysis.  The findings related to preventability are based 
on determinations made by the physician reviewers for each adverse 
event and temporary harm event.  We calculated percentages for each 
preventability classification and for different types of events, the results 
of which are projectable to the population.  We also conducted statistical 
tests to identify differences in preventability rates between adverse 
events and temporary harm events and across various categories of 
adverse events, such as medication-related and infection-related events.   
Medicare cost analysis.  We estimated the cost to Medicare resulting 
from care associated with adverse events and temporary harm events.  
This analysis included only Medicare claims that were paid under the 
IPPS and were subject to the Medicare HAC policy (84 percent of 
sample beneficiaries).47   Certified medical coders reviewed the medical 
records, the medical review protocols, and the associated Medicare 
claims to identify diagnosis and procedure codes that would not have 
been included in the claims if the events had not occurred.  We then 
used CMSs MS-DRG Grouper and Medicare Code Editor Version 27 
(Grouper) to determine the DRG for the claims and used the FY 2009 
IPPS personal computer Pricer (Pricer) to determine the resulting 
Medicare reimbursement amounts.48  For each claim, we calculated the 
DRG and reimbursement amount, including information from the 
 
46 K.M. Arias, Outbreak Investigation, Prevention, and Control in Health Care Settings, 
Second Edition, Jones and Bartlett Publishers, 2009, pp. 330331.  
47 The cost analysis does not include claims for beneficiaries whose Medicare coverage is 
not paid under the IPPS.  This includes Medicare managed care organizations and care 
provided at hospitals excluded from the Medicare IPPS system, including hospitals in the 
State of Maryland and some specialty hospitals nationwide, such as cancer treatment centers 
and critical access hospitals.  CMS, HAC Fact Sheet.  Accessed at 
http://www.cms.gov/HospitalAcqCond/Downloads/HACFactsheet.pdf on September 29, 2010. 
48 The Grouper software classifies hospital claims into MS-DRG categories expected to 
have similar hospital resource requirements.  MS-DRGs are based on the nine diagnoses 
associated with HACs and corresponding POA indicators, six procedure codes, and 
demographic data contained in the NCHs.  MS-DRGs typically split into two or three 
individual classes based on the presence of a complication or comorbidity.  This software was 
developed by CMS and 3M and is sold by the National Technical Information Service.  
Accessed at http://www.ntis.gov on September 29, 2010. 
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I N T R O D U C T I O N  
hospital Medicare claim.  We then calculated the reimbursement 
amount excluding diagnosis and procedure codes that coders 
determined were the direct result of any adverse event or temporary 
harm event experienced by the beneficiary.  We projected the difference 
between the two hospital reimbursement amounts to estimate the 
additional cost to Medicare for care associated with events.  When an 
entire hospital stay was the result of an adverse event, we included the 
total reimbursement amounts indicated by the Pricer as the cost of the 
adverse event.     
Limitations 
Beyond the challenges associated with identifying adverse events and 
assessing preventability, the methodology presents two specific 
limitations.  First, it is unlikely that the study identified all adverse and 
temporary harm events within the sample.  To the extent that the study 
did not identify an event, it was likely because the three screening 
methods failed to flag the case for physician review or because 
documentation in the medical records was incomplete.  Second, cost 
estimates did not include all costs of care associated with events, 
excluding stays not covered under the Medicare IPPS, additional 
hospital stays caused by sample events but occurring after  
October 2008, additional care outside the hospital (such as followup 
physician office visits or rehabilitation services), and changes in 
Medicare outlier payments.49   
Standards 
This study was conducted in accordance with the Quality Standards for 
Inspections approved by the Council of the Inspectors General on 
Integrity and Efficiency.
 
49 Medicare outlier payments are supplemental payments to hospitals for patients who 
incur extraordinarily high costs.  Outlier payments are based on the degree to which costs on a 
claim exceed specific hospital and MS-DRG fixed-loss thresholds and fluctuate depending on 
the MS-DRG to which the claim is grouped.  The Pricer analysis involved a revision of the  
MS-DRG.  This revision resulted in new outlier payments for three sample cases and 
increased outlier payments for two sample cases.  The revised outlier payments decreased the 
cost attributed to adverse events in our estimate.  
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  14  
 FF II NN DD II NN GG SS   
F I N D I N G S  
An estimated 13.5 percent of hospitalized  Of the nearly 1 million Medicare 
Medicare beneficiaries experienced adverse  beneficiaries discharged from 
hospitals in October 2008, about  
events during their hospital stays 
1 in 7 experienced an adverse 
event (13.5 percent), defined as an event that met at least 1 of the 
following 3 criteria:  the event was on the NQF list of Serious 
Reportable Events; the event was on Medicares list of HACs; or the 
event resulted in 1 of the 4 most serious categories on the NCC MERP 
index (prolonged hospital stay, permanent harm, life-sustaining 
intervention, or death).  This incidence rate projects to approximately 
134,000 Medicare beneficiaries experiencing at least 1 adverse event in 
hospitals during the study period.  Table 2 lists the incidence rate for 
each of the three criteria. 
Table 2:  Estimated National Incidence of Adverse Events Among 
Medicare Beneficiaries Discharged in October 2008 
  Estimated  Estimated 
Percentage of  Number of 
Category of Events 
Medicare  Medicare 
Beneficiaries  Beneficiaries 
 
NQF Serious Reportable Events*  0.6%  6,367 
 
Medicare HACs*  1.0%  10,187 
 
NCC MERP F-I Level Events  13.1%  129,890 
 
(Overlap)**  (1.3%)  (12,734) 
 
           Total  13.5%***  133,710 
  See Appendix F for confidence intervals.  
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision.  
**The 1.3 percent represents beneficiaries who experienced adverse events in more than one category.  We 
counted these beneficiaries only once in determining the overall incidence rate.  
***Column does not sum to 13.5 percent because of rounding. 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008. 
 
We classified the identified adverse events into four clinical categories:  
events related to medication (31 percent), events related to ongoing 
patient care (28 percent), events related to surgery or other procedures  
(26 percent), and events related to infection (15 percent).  Table 3 lists 
the 128 adverse events found in the sample within these categories.  See 
Appendix H for a list of the events with more complete descriptions, the 
level of harm patients incurred, and indications of whether the events 
were on the NQF and HAC lists. 
 
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F I N D I N G S  
Table 3:  Adverse Events Identified Among Sample Medicare 
B  eneficiaries by Clinical Category (n=128) 
Number of Events 
Types of Adverse Events  and Percentages of 
 
Total Events 
Events Related to Medication  31% (40) 
   Excessive bleeding  12 
  Delirium or change in mental status  7 
   Hypoglycemic event  6 
  Acute renal insufficiency (kidney failure)  4 
  Severe hypotension  4 
 
  Respiratory complications  4 
  Severe allergic reactions  3 
 
Events Related to Patient Care  28% (36) 
  Intravenous volume overload  10 
 
  Aspiration  8 
  Deep vein thrombosis or pulmonary embolism  5 
   Exacerbation of preexisting medical condition  5 
  Stage III pressure ulcer  3 
  Breakdown of surgical wound  1 
 
  Congestive heart failure  1 
  Hypoxia (oxygen deficiency)  1 
 
  Patient fall with injury  1 
  Prolonged weakness and dizziness  1 
E vents Related to Surgery or Other Procedures  26% (33) 
  Excessive bleeding  5 
   Severe hypotension  4 
  Respiratory complication  4 
   Iatrogenic pneumothorax  3 
  Postoperative ileus  3 
  Postoperative urinary retention  3 
 
  Acute coronary syndrome  2 
  Blood clot and other occlusion  2 
   Cardiac complication  2 
  Cardiac dysrhythmia  1 
   Delay in surgery because of equipment malfunction  1 
  Hemorrhage at surgical site  1 
  Seroma (fluid) following stomach resection  1 
 
  Urinary catheter-associated trauma  1 
Events Related to Infection  15% (19) 
 
  Urinary tract infection  5 
  Vascular catheter-associated infection (central or peripheral line)    4 
 
  Other bloodstream infection  4 
  Respiratory infection  4 
   Surgical or procedural site infection  2 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries in October 2008.  
 
Of beneficiaries who experienced adverse events, 18 percent had  
more than one adverse event.  Most of the beneficiaries who experienced 
multiple events had two events, but others had as many as three 
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F I N D I N G S  
unrelated events in the same hospitalization.  For example, an elderly 
heart patient with a history of mental illness experienced three adverse 
events of different types, including two events that prolonged 
hospitalization and a third that required life-sustaining intervention.  
(This beneficiary also experienced three temporary harm events 
associated with patient care.)     
Less than 1 percent of Medicare beneficiaries experienced an event on 
the NQF list of Serious Reportable Events  
An estimated 0.6 percent of Medicare beneficiaries experienced an event 
on the NQF list, which projects to approximately 6,400 beneficiaries 
nationally for the study period.  The low number of NQF events in the 
sample is notable because of the prominence of the list as a measure of 
patient harm and its use by a number of State adverse event reporting 
systems and other entities.  We identified a total of five NQF events in 
the sample:  two medication-related deaths and three Stage III pressure 
ulcers.50  One of the medication-related deaths illustrates the nature of 
the NQF list as a measure of the most egregious preventable outcomes.  
In this case, a disabled Medicare beneficiary with muscular dystrophy 
affecting the respiratory system entered the hospital for signs of 
respiratory failure.  Medical staff at the hospital gave the beneficiary a 
medication known to further suppress respiration, resulting in 
progressive respiratory distress and subsequent death.  Physician 
reviewers concluded that medical staff administered the wrong 
medication because they lacked clinical understanding of the patients 
unique condition.   
Many serious events that we identified were not on the NQF list of 
Serious Reportable Events, including some events that resulted in 
patient deaths and serious disability.  The NQF list focuses largely on 
serious disability or death, but is restricted to a specific set of events.  
Of the 18 adverse events that physician reviewers found to result in 
serious disability or patient death, only 2 were on the NQF list (i.e., the 
medication errors resulting in death).  The three Stage III pressure 
ulcers identified in the sample were sufficiently treated prior to 
 
50 Pressure ulcers are classified into four stages by the National Pressure Ulcer Advisory 
Panel (NPUAP):  Stage I is intact skin with nonblanchable redness; Stage II is a shallow ulcer 
or blister indicating damage to the epidermis; Stage III is damage extending through all the 
layers of the skin; and Stage IV is damage through all the layers of the skin and underlying 
muscle, tendons, or bone.  NPUAP, Pressure Ulcer Stages Revised by NPUAP.  Accessed at  
http://www.npuap.org on November 12, 2009.  
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F I N D I N G S  
discharge from the hospital and determined by physicians to have 
caused only temporary harm.   
Medicare HACs rarely occurred, affecting just 1 percent of beneficiaries 
An estimated 1 percent of hospitalized Medicare beneficiaries 
experienced Medicare HACs, which projects to approximately 10,000 
beneficiaries nationally.  We identified a total of nine Medicare HACs 
experienced by beneficiaries in the sample:  five catheter-associated 
urinary tract infections, two vascular catheter-associated infections of 
the central line, one patient fall resulting in injury (a compression 
fracture), and one Stage III pressure ulcer.  One beneficiary experienced 
two of these events, resulting in a total of eight sample beneficiaries 
with Medicare HACs.  Two catheter-associated urinary tract infections 
caused more substantial harm than is typically associated with this 
condition:  one resulted in a prolonged hospital stay and the other in 
permanent harm.  The two vascular catheter-associated infections of a 
central line resulted in prolonged hospital stays.  None of the nine 
Medicare HACs identified by physicians on the medical records were 
included in the associated Medicare claims.  In four of the nine cases (all 
catheter-associated urinary tract infections), diagnosis codes on the 
claims identified the infections, but they were not the precise codes that 
CMS uses to identify these HACs.  The other five claims had no 
diagnosis codes related to the HACs.  Therefore, the HACs were not 
identifiable through the claims data that CMS uses to implement the 
HAC policy.   
Thirteen percent of Medicare beneficiaries experienced adverse events 
classified in the most serious categories on the NCC MERP harm index 
Based on our physician medical review, 13.1 percent of Medicare 
beneficiaries experienced adverse events classified in the four most 
serious harm categories on the NCC MERP harm index:  events 
resulting in prolonged hospital stay, events resulting in permanent 
harm, events requiring life-sustaining intervention, and events 
contributing to death.  This rate projects nationally to approximately 
130,000 beneficiaries experiencing such adverse events during the study 
period.  Often, adverse events within the same clinical category, such as 
infection, resulted in a different level of harm depending on the 
intervention required and the condition of the patient.  Table 4 lists the 
percentage of adverse events in the sample that were classified in the 
four most serious harm categories and the projected national numbers 
of events by level of patient harm. 
 
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F I N D I N G S  
  Table 4:  Adverse Events Classified as F-I on the NCC MERP 
Patient Harm Index by Level of Harm  
 
Level of Harm   Percentage of Adverse Events 
 
F level:  Requiring prolonged hospital stay  62%  
 
G level:  Permanent harm*  5% 
 
H level:  Life-sustaining intervention required  23% 
 
I level:  Contributing to death*  10% 
  See Appendix F for confidence intervals. 
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision.   
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008. 
An estimated 1.5 percent of hospitalized Medicare beneficiaries 
experienced events that contributed to their deaths  
Among the 128 adverse events that we identified in the sample,  
12 events (9 percent of 128 events) contributed to the deaths of 
beneficiaries.  This projects to an estimated 1.5 percent of hospitalized 
Medicare beneficiaries experiencing events that contributed to death or 
approximately 15,000 beneficiaries during the study period.  Seven of 
the twelve deaths were related to medication, either the result of 
improper administration of medication (wrong drug or wrong dosage) or 
inadequate treatment of known side effects.  The most common type of 
medication-related death (five deaths) involved excessive bleeding from 
blood-thinning medication.  The two other medication-related deaths 
involved inadequate insulin management resulting in hypoglycemic 
coma and respiratory failure resulting from oversedation.  Of the five 
non-medication-related deaths, two were from bloodstream infections; 
two involved aspiration (which led to pneumonia and cardiac arrest, 
respectively); and the other involved a ventilator-associated pneumonia.  
As stated previously, only 2 of the 12 adverse events that contributed to 
death were on the NQF list and none were Medicare HACs. 
Twenty-seven percent of beneficiaries who experienced adverse events had 
at least one cascade event, wherein multiple, related events occurred in 
succession 
The sample included a total of 28 cascade events, defined as adverse 
events that included a series of multiple, related events.  We counted 
these as single events.  These cascade events were some of the most 
serious adverse events identified in the sample, with nine cases 
requiring life-sustaining intervention and six cases contributing to 
death.  The most common type of cascade events were events related to 
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F I N D I N G S  
surgery and other procedures (nine events).  Two of these events began 
with excessive bleeding following surgery or a procedure.  For example, 
one beneficiary had excessive bleeding after his kidney dialysis needle 
was inadvertently removed, which resulted in circulatory shock, a 
transfer to the intensive care unit, and emergency insertion of a tube 
into the trachea (windpipe) to ease breathing.  When the tube was 
removed the following day, the patient aspirated (inhaled foreign 
material into his lungs), which required a life-sustaining intervention.   
 
An additional 13.5 percent of 
An additional 13.5 percent of Medicare 
Medicare beneficiaries 
beneficiaries experienced events during their 
experienced events during the 
hospital stays that resulted in temporary harm 
study period classified as E level 
harm on the NCC MERP index, defined as events that required medical 
intervention but did not cause lasting harm.  This rate projects to 
approximately 134,000 Medicare beneficiaries experiencing temporary 
harm events during the study period.  Of these beneficiaries, 22 percent 
had more than one unrelated event (the highest occurrence was five 
unrelated events in a single hospital stay).  Additionally, 28 percent of 
beneficiaries who experienced adverse events (and are included in our 
primary rate) also had temporary harm events during the same stay.   
Events classified as temporary harm represented a wide array of 
conditions, such as prolonged vomiting and hypoglycemia (see Table 5).  
The most common events related to medication (42 percent).  Although 
many cases of temporary harm represented fairly minor occurrences, we 
classified others as temporary because the patients were in the hospital 
for a lengthy period because of other, more serious, diagnoses, allowing 
the hospital enough time to address the harm prior to discharge.  
Physician reviewers indicated that many temporary harm events could 
have developed into more serious adverse events, but hospitals provided 
timely intervention.  For example, Stage I or Stage II pressure ulcers 
can escalate quickly to Stage III or Stage IV without proper care51 and 
episodes of hypoglycemia can lead to stroke and even death.52          
 
51 J.L. Zeller, C. Lynm, and R.M. Glass, Pressure Ulcers, Journal of the AMA, 296(8), 
August 23/30, 2006, p. 1020.  Accessed at http://jama.ama-assn.org on December 1, 2009. 
52 P. Mandava and T. Kent, Metabolic Disease & Stroke:  Hyperglycemia/Hypoglycemia, 
Journal of Diabetes Science and Technology, 17, April 4, 2006, p. 8.  Accessed at 
http://emedicine.medscape.com on December 1, 2009. 
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Table H-2 in Appendix H contains a list of the 174 temporary harm 
events identified in the sample with more complete descriptions. 
 
Table 5:  Temporary Harm Events Identified Among Sample 
Medicare Beneficiaries by Clinical Category (n=174) 
 
Number of Events and 
Ty pes of Temporary Harm Events  Percentage of Total  
Events 
 
Events Related to Medication  42% (73) 
 
  Delirium or change in mental status  22 
  Hypoglycemic event  11 
  Thrush and other opportunistic infection   7 
  Allergic reaction or side effect related to skin  6 
  Gastrointestinal complication  5 
  Hypotension  5 
  Dysrhythmia  3 
  Excessive bleeding  3 
  Severe headache or dizziness  3 
  Acute renal failure or insufficiency  2 
  Allergic reaction to blood or related products  2 
  Respiratory complication  2 
  Other events related to medication  2 
Events Related to Patient Care  36% (63) 
  Stage I, Stage II, or unstaged pressure ulcer  20 
  Intravenous volume overload  15 
  Skin tear, laceration, abrasion, or other breakdown  9 
  Intravenous infiltrate with symptoms  6 
  Patient fall with injury    5 
  Aspiration  3 
  Failure to treat constipation or obstipation  3 
  Tachycardia or dysrhythmia  2 
Events Related to Surgery or Other Procedures  18% (32) 
  Urinary retention  8 
  Excessive bleeding  6 
  Cardiac complication  4 
  Surgical tear or laceration  3 
  Urinary catheter-related trauma  3 
  Prolonged nausea and vomiting  2 
  Postoperative or postprocedural hypotension  2 
  Respiratory complication  2 
  Other events related to surgery or other procedures  2 
Events Related to Infection  4% (6) 
  Surgical site infection  2 
  Bacterial infection  1 
  Respiratory infection  1 
  Urinary tract infection  1 
  Vascular catheter-associated infection   1 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries in October 2008.  
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Physician reviewers assessed the 
Physician reviewers determined that  
extent to which events were 
44 percent of adverse events and temporary 
preventable based on information 
harm events were clearly or likely preventable 
in the medical records, their 
clinical experience with similar circumstances, research literature about 
the preventability of specific events, and group discussion to reach 
consensus.  Combining adverse events and temporary harm events, 
physicians determined that 44 percent were preventable and 51 percent 
were not preventable.53  (There was no statistically significant 
difference between the preventability rates of adverse events and 
temporary harm events.)54  For the remaining 5 percent of events, 
physicians were unable to make determinations because of incomplete 
documentation in the medical records or extreme complexities in the 
patients conditions or in the hospital care provided.  Table 6 provides 
the percentage of events by the physician preventability assessment.   
  Table 6:  Events by Physician Preventability Assessment 
Preventability Assessment   Percentage of Events 
 
PreventableHarm could have been avoided through 
improved assessment or alternative actions   44% 
Clearly preventable  9% 
Likely preventable  35% 
Not preventableHarm could not have been avoided given 
the complexity of the patients condition or care required  51% 
Clearly not preventable   18% 
Likely not preventable  33% 
Unable To Determine Preventability   5% 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008. 
Physician reviewers assessed the preventability of events similarly for 
three of the four clinical categories (medication, patient care, and 
infections).  However, events related to surgery and other procedures 
were significantly less likely to be determined preventable than events in 
the other three clinical categories; only 17 percent of surgical events were 
 
53 The preventability rate of 44 percent is similar to the rate of 43.5 percent found by a 
2008 review of 8 adverse event preventability studies previously referenced on p. 7. 
54 The Cochran-Mantel-Haenszel chi square test was not significant at the 95-percent 
confidence level (p=0.0568).  See Appendix F for detailed preventability statistics for adverse 
events and temporary harm events.  
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preventable in contrast to 50 percent or more in each of the other three 
groups.55  Physician reviewers indicated that the reasons surgical events 
were more likely to be assessed as not preventable were the high level of 
complexity in both the care involved and the patients conditions.  Table 7 
provides the percentage of preventable events by clinical category.   
  Table 7:  Preventable Events Within Clinical Categories  
Percentage of Events 
Clinical Category 
Assessed as Preventable 
Infection  60% 
Medication   50% 
Patient care  51% 
Surgery and other procedures   17% 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008. 
Within the clinical categories, physician reviewers sometimes gave the 
same preventability assessment for events with similar characteristics.  
For example, they assessed 10 of 12 events related to allergic reactions 
as not preventable.  But for other types of events, preventability 
determinations for similar events differed based on the patients 
conditions and risk factors.  For example, in two cases of excessive 
stomach bleeding caused by blood thinners, physicians assessed one 
event affecting a relatively healthy patient as preventable and the other 
event affecting a patient with stomach ulcers as not preventable 
because of the patients susceptibility.  In another case, physician 
reviewers determined that some pressure ulcers were not preventable 
because of the poor conditions of the patients and because 
documentation in the medical records showed that the hospital staff 
employed appropriate preventive care.  However, physicians assessed 
another pressure ulcer case as preventable because the medical staff 
declined to order a specialty mattress for an at-risk bedridden patient 
until after the pressure ulcer had developed, even though the medical 
record indicated that the specialty bed was available.  
  
 
55 The Cochran-Mantel-Haenszel chi square test was significant at the 95-percent 
confidence level for the overall relationship between preventability and clinical category 
(p<0.0001) as well as for each set of pair-wise comparisons between the surgical category and 
each of the other three clinical categories (p<0.01 for each pair).  Preventability rates were    
62 percent for infections, 50 percent for medication, and 50 percent for patient care. 
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Counting only preventable events, the estimated national incidence rate of 
adverse events among Medicare beneficiaries would be 7.4 percent 
The estimated adverse event incidence rate of 13.5 percent is based on 
all adverse events meeting one of the three criteria, regardless of 
whether the events were preventable.  Including only the adverse 
events determined by physician reviewers to be clearly or likely 
preventable, the estimated incidence rate of adverse events among 
Medicare beneficiaries would be 7.4 percent.  The 13.5 percent rate of 
additional beneficiaries experiencing temporary harm events would be 
6.3 percent if only preventable events were included.  
Eleven of the thirteen NQF Serious Reportable Events and Medicare HACs  
in the sample were preventable, a key criterion of both lists 
Although we found few in the sample, all but two adverse events on the 
NQF and HAC lists were assessed as clearly or likely preventable.56  
After the adverse events on each list were separated, four of the five 
events on the NQF list were preventable and eight of the nine Medicare 
HACs were preventable (one event was on both lists).  A key criterion of 
both lists is that the events be largely preventable.  The two events on 
the lists that physicians assessed as not preventable were (1) an NQF 
event consisting of a pressure ulcer that progressed from Stage I to 
Stage III in a chronically ill patient with multiple complications and 
susceptibility to skin breakdown and (2) a Medicare HAC consisting of a 
compression fracture incurred during a fall by a morbidly obese patient. 
Preventable events were most commonly linked to medical errors, 
substandard treatment, and inadequate patient monitoring or assessment 
Physician reviewers selected one or more rationales to support each 
preventability determination from a list developed by the physician 
panel.  To develop these rationales, physicians gleaned information from 
medical records, such as clinical staff actions, hospital environmental 
factors, and patient condition unrelated to the event.  Among events 
assessed as preventable, 58 percent were linked to errors by clinical 
staff in medical judgment, skill, or patient management.  Such errors 
often involved prescribing or administering the wrong medication.  
Nearly half of preventable events (46 percent) involved care provided in 
a substandard way, most frequently because of delay in diagnosis or 
 
56 The number of NQF and HAC events was too small to test the preventability measure for 
statistical significance with an acceptable degree of precision or to project the measure to the 
national sampling frame. 
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F I N D I N G S  
treatment.  Table 8 provides physician preventability rationales for 
events within each assessment category. 
Table 8:  Events by Physician Preventability Rationales  
Percentage 
Preventability Rationale 
of Events* 
Preventable Events (n=133)  
Error was related to medical judgment, skill, or patient management   58% 
Appropriate treatment was provided in a substandard way  46% 
The patients progress was not adequately monitored  38% 
The patients health status was not adequately assessed  23% 
Necessary treatment was not provided  17% 
Event rarely happens when proper precautions and procedures are followed**  14% 
Communication between caregivers was poor**  8% 
Facilitys patient safety systems and policies were inadequate or flawed**  3% 
Breakdown in hospital environment occurred (equipment failure, etc.)**  2% 
Nonpreventable Events (n=155) 
Event occurred despite proper assessment and procedures followed  62% 
Patient was highly susceptible to event because of health status   50% 
Care provider could not have anticipated event given information available  35% 
Patients diagnosis was unusual or complex, making care difficult  29% 
Harm was anticipated but risk considered acceptable given alternatives**  14% 
See Appendix F for confidence intervals. 
*Percentages do not add to 100 because physician reviewers often selected more than 1 rationale. 
**Given the small percentages, confidence intervals for projected numbers exceed 50-percent relative precision.   
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008.  
Other common factors associated with preventable events were 
inadequate monitoring of patients (38 percent) and inadequate 
assessment of patients (23 percent).  These factors often led to delays in 
treatment and worsening of patient conditions.  In several of these 
cases, patients displayed symptoms of infection but were not given 
antibiotics until they reached the point of sepsis.  In one case, the 
patient exhibited signs of shock upon arrival at the hospital, but clinical 
staff did not monitor the patients blood pressure for the first 8 hours 
and did not provide related treatment for another 16 hours.  This delay 
caused the patient to experience severe hypotension, requiring           
life-sustaining intervention.   
 
 
 
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F I N D I N G S  
Physician reviewers assessed events as clearly or likely not preventable 
when the events occurred despite proper procedures or when the 
patients were highly susceptible to the events  
For 62 percent of the nonpreventable events in our sample, physician 
reviewers found that care was rendered according to accepted standards 
of practice.  In these cases, physicians determined that the care 
provided was sufficient and appropriate and that there was no evidence 
of errors or other problems.  This rationale was often given in 
combination with the second most common factorthat the patients 
other conditions made them highly susceptible to the event (50 percent 
of nonpreventable events).  For example, one beneficiary, admitted to 
the hospital with a bowel obstruction, experienced a surgical cut of the 
intestine that would have been difficult to avoid because of significant 
damage to the bowel from prior surgery.   
Other common rationales for assessing events as not preventable also 
focused on the difficulty of providing care.  For 35 percent of 
nonpreventable events, physicians determined that the medical and 
hospital staff could not have anticipated the events given information 
available about the patients at the time of care delivery.  For 29 percent 
of nonpreventable events, physicians determined that the patients 
diagnoses were unusual or complex, making care particularly difficult.  
Finally, in 14 percent of nonpreventable cases, the adverse events were 
anticipated by caregivers, but the harm associated with the adverse 
events was considered less harmful than not providing care.  For 
example, in four sample cases, patients experienced harm as a result of 
an overload of intravenous fluid, yet the medical review found that the 
patients were in such dire need of fluids (e.g., at risk for hypoglycemic 
shock) that caregivers had little choice but to execute vigorous 
intravenous fluid replacement despite the risk of overload.   
 
 
 
 
 
 
 
 
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FF II NN DD II NN GG SS   
Hospital care associated with adverse events  Sixteen percent of sample 
and temporary harm events cost Medicare an  beneficiaries under the Medicare 
IPPS who experienced events 
estimated $324 million in October 2008 
incurred additional Medicare 
hospital costs as a result.  Most of the additional costs (87 percent) 
resulted from care associated with adverse events, with temporary 
harm events generating the remaining costs.57  These additional costs 
project to an estimated $324 million, which equates to 3.5 percent of the 
$9.2 billion that Medicare spent for inpatient care during  
October 2008.58  To give these figures an annual context, 3.5 percent of 
the   $137 billion Medicare inpatient expenditure in FY 2009 equates to    
$4.4 billion spent on care associated with adverse events.59    
Costs associated with preventable events accounted for an estimated 
$119 million of the $324 million additional cost, equating to 1.3 percent 
of the $9.2 billion Medicare inpatient expenditures for the month or 
about $1.8 billion annually.  
Despite this outlay, most events did not affect Medicare costs; none of 
the Medicare HACs resulted in a higher reimbursement  
Of beneficiaries who experienced adverse events or temporary harm 
events in hospitals covered under the Medicare IPPS, 84 percent did not 
incur additional costs for care associated with the events.  This occurred 
primarily because many Medicare claims for beneficiaries who 
experienced events did not include diagnosis or procedure codes relating 
to the events.  When Medicare claims included codes associated with the 
events, the codes often had no effect on costs because the claims 
included other costly diagnoses or procedure codes that elevated the 
reimbursement to equivalent or higher amounts.   
 
57 One Medicare claim included codes for two eventsone adverse event and one temporary 
harm eventand incurred an identical payment impact.  This claim overlaps both groups and 
consequently the percentages do not total 100 percent:  87 percent of costs resulted from care 
associated with adverse events and 15 percent of costs resulted from care associated with 
temporary harm events. 
58 These cost estimates include only claims under the IPPS, representing 708 sample 
Medicare claims (85 percent), but do not include costs for the remaining 130 sample 
beneficiaries (15 percent) who had sample admissions not covered under IPPS. 
59 The annual cost estimate of $4.4 billion is 3.5 percent of the $137 billion Medicare 
inpatient costs for FY 2009, which assumes the same proportion of costs for adverse events for 
the other 11 months that we found in October 2008.  Annual Medicare inpatient cost figures 
are from CMS, 2009 CMS Statistics Book, Table III.6, Office of Research, Development, and 
Information, CMS Pub. No. 03497, December 2009, p. 30.  
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F I N D I N G S  
None of the nine Medicare HACs identified in the sample resulted in a 
higher level of Medicare reimbursement.  Although the Medicare HAC 
policy is intended to limit costs associated with the specified events, our 
review showed that none of the HACs in the sample would have invoked 
a higher Medicare reimbursement.  None of the associated Medicare 
claims included the specific diagnosis codes that CMS uses to identify 
HACs.  However, even if the codes had been included on the claims, the 
HAC policy would still not have resulted in payment reductions for 
these cases because other diagnosis or procedure codes would have 
elevated the reimbursement to a higher amount.   
Two-thirds of Medicare costs associated with events were the result of 
additional hospital stays necessitated by harm from events 
Sixty-five percent of the additional costs to Medicare ($210 million of 
the $324 million) were the result of entire, additional hospital stays 
required to treat the harm resulting from the adverse events.  In some 
of these cases, the events occurred during outpatient services at the 
hospital (such as an emergency room visit or an outpatient surgery) and 
necessitated unplanned admissions to the inpatient facilities.  In other 
cases, the events occurred during inpatient care and the beneficiaries 
were released from the hospital, but the aftereffects of the events 
necessitated subsequent hospital stays within the study period.  The 
average Medicare cost of these additional hospital stays for sample 
beneficiaries was $13,745, compared with an average additional cost of 
$5,601 for event-related care that hospitals provided during the initial 
hospital stay in situations that did not necessitate additional stays.60, 61   
Medicare cost estimates do not include additional costs required for 
followup care after the sample hospitalization  
Because our cost analysis included only hospital stays that ended 
during October 2008, Medicare costs associated with care resulting from 
adverse events and temporary harm events are greater than our 
estimate.  Beneficiaries may have had additional event-related hospital 
stays beyond our study period and may have incurred expenses to 
Medicare or personal expenses for followup care not reflected in 
inpatient claims, such as physician office visits, medication, and 
rehabilitation services during and after our study period.   
 
60 Averages reflect only costs greater than zero. 
61 The Students T-test comparing difference of means was significant at the 95-percent 
confidence level (p=0.0104). 
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As an example of an event resulting in subsequent Medicare costs not 
captured by our cost analysis, one sample beneficiary was initially 
admitted to the hospital in mid-October 2008 for a stroke.  During this 
hospital stay, he experienced an allergic reaction to medication and was 
discharged with no additional cost associated with the event.  However, 
following discharge, the allergic reaction progressed to a  
life-threatening condition known as Stevens-Johnson Syndrome.62  The 
beneficiary returned to the hospital during October for treatment, 
incurring the cost of an entire hospital stay as a result of the event, but 
was misdiagnosed and again discharged.  The patient then incurred two 
additional hospital stays within the next 30 days to correctly diagnose 
and treat the condition.  The total estimated inpatient cost to Medicare 
for the latter three hospital stays was $43,050, all necessitated by the 
event.  Only $10,982 of this amount was incurred during the study 
period and included in our cost estimate.  Physician reviewers 
determined that the medication-related event was preventable because 
the medication was known to be highly reactive and the condition was 
not diagnosed correctly, delaying treatment.  
 
62 This condition typically begins with a skin rash and fever and, if untreated, progresses to 
an array of conditions constituting serious harm, such as lung damage and renal failure.  
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 RR EE CC OO MM MM EE NN DD AA TT II OO NN SS   
In the decade since the IOM report, the need to improve patient safety 
has received much attention from Federal and State governments, 
advocacy groups, and the health care industry.  Despite this attention, 
we found that 13.5 percent of Medicare beneficiaries experienced 
adverse events during their hospital stays in October 2008, most of 
which resulted in prolonged hospital stays, permanent harm,  
life-sustaining interventions, or death.  An additional 13.5 percent of 
beneficiaries experienced temporary harm as the result of events.  
Physician reviewers determined that 44 percent of events were 
preventable and that preventable events often involved medical errors, 
substandard care, and inadequate monitoring or assessment of patients.  
We found that in addition to causing the harm to patients, adverse 
events and temporary harm events increased costs to Medicare by an 
estimated $324 million in a single month, or 3.5 percent of Medicare 
inpatient expenditures, suggesting potential savings from reducing the 
incidence of events.     
As the Federal Governments principal agency for protecting the health 
of Americans,63 HHS is uniquely positioned to lead national efforts to 
reduce adverse events in hospitals.  As part of the national strategy to 
improve health care quality mandated by the ACA, HHS is to identify 
areas in the delivery of health care services that have the potential for 
rapid improvement in the quality and efficiency of patient care.64   
Because many adverse events that we identified were preventable, our 
study confirms the need and opportunity for hospitals to significantly 
reduce the incidence of events.  A number of agencies within HHS share 
responsibility for addressing this issue, most prominently AHRQ as a 
coordinating body for efforts to improve health care quality and CMS as 
the Nations largest health care payer and an oversight entity. 
Therefore, we recommend the following:  
AHRQ and CMS should broaden patient safety efforts to include all 
types of adverse events  
Efforts to improve patient safety often focus on a small subset of 
events that harm hospital patients.  For example, NQF Serious 
Reportable Events or Medicare HACs represented only a fraction of 
 
63 HHS, HHS Agency Mission Statement, updated February 2004.  Accessed at 
http://www.hhs.gov/about/ on March 23, 2010.  
64 P.L. 111-148  3501. 
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R E C O M M E N D A T I O N S  
the adverse events we identified in this report.  Additionally, 
patient safety provisions in the ACA often refer specifically to 
reducing medical errors, rather than to the broader range of adverse 
events.  AHRQ and CMS should avoid focusing patient safety efforts 
too narrowly on a small list of specific events, possibly failing to 
address the wider array of events that lead to most instances of 
patient harm.  Rather, AHRQ and CMS should promote a definition of 
adverse events that more fully encompasses harm resulting from 
medical care.  This broader definition would apply to a number of 
patient safety activities, including setting priorities for research, 
establishing guidelines for hospital reporting of events, developing 
prevention strategies, measuring health care quality, and 
determining payment policies. 
AHRQ and CMS should enhance efforts to identify adverse events  
Identifying adverse events assists policymakers and clinical researchers 
in directing prevention resources to the areas of greatest need, setting 
clear goals for improvement, assessing the effectiveness of specific 
strategies, holding hospitals accountable, and gauging progress in 
reducing incidence. 
  AHRQ should sponsor periodic, ongoing measurement of the 
incidence of adverse events.  To facilitate measurement, AHRQ 
should establish a standard protocol for identifying events and 
analyzing information about incidence and causes.  AHRQ should 
also consider providing hospitals with methods for measuring their 
incidence of events, goals for incidence reduction, and benchmarks 
or other means for comparing rates among providers.   
  AHRQ should continue to encourage hospitals to report to PSOs.  
Hospital reporting of adverse event information to PSOs can provide 
AHRQ with aggregated data about the nature and causes of events.  
To maximize the usefulness of PSO-reported data for national 
measurement and analysis, AHRQ should continue working toward 
establishing standard adverse event definitions and reporting 
formats and encouraging hospital reporting.   
  CMS should use POA indicators in hospital billing data to calculate 
the frequency of adverse events occurring within hospitals.  These 
POA indicator data represent a rich source of information for 
identifying certain adverse events in claims data.  CMS should 
establish routine methods for using POA indicators to guide patient 
safety improvement efforts.  For example, CMS could direct that 
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R E C O M M E N D A T I O N S  
QIOs use POA indicators to monitor hospital rates of specific 
conditions.   
CMS should provide further incentives for hospitals to reduce the 
incidence of adverse events through its payment and oversight functions  
CMS, as both a payer and an oversight entity, is positioned to influence 
hospitals to provide high-quality care.  CMS should explore avenues to 
reduce the incidence of adverse events through both program 
participation and payment policy.   
  CMS should strengthen the Medicare HAC policy.  We found that 
HACs represent a small proportion of preventable events and that 
they are not always coded as such in Medicare claims.  The ACA 
makes several changes to the HAC policy, including allowing the 
Secretary to expand the list of HACs.  The law also gives the HAC 
policy greater significance by using the list of HACs to implement 
Medicare payment penalties, create performance measures, and 
prohibit Medicaid payments for associated care.  Given their low 
incidence, continued use of the 10 HACs already established by CMS 
may limit the intended effect of the statute.  To strengthen the 
policy, CMS should consider expanding the list of Medicare HACs to 
include more conditions that may result in harm to beneficiaries.  
CMS should also take additional steps to ensure that hospitals 
accurately code Medicare claims to show when HACs occur, as 
recommended in our prior report.65   
  CMS should look for opportunities to hold hospitals accountable for 
adoption of evidence-based practice guidelines.  The conditions of 
participation for Medicare and Medicaid require that hospitals have 
programs to demonstrate quality improvement where evidence 
shows practices can improve outcomes.  CMS should further 
influence hospitals to reduce adverse events through enforcement of 
the conditions of participation.  This could include more closely 
examining patient safety issues through the survey and certification 
process, as recommended in our prior report.66  This could also 
include encouraging hospitals to adopt evidence-based practices 
shown to prevent adverse events. 
 
65 OIG, Adverse Events in Hospitals:  Methods for Identifying Events, OEI-06-08-00221, 
March 2010. 
66 Ibid. 
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R E C O M M E N D A T I O N S  
AGENCY COMMENTS 
We received comments on the draft report from AHRQ and CMS.  
AHRQ.  AHRQ concurred with our recommendations, stating that 
adverse events affect hospital patients at an alarming rate and that it 
must continue working to improve patient safety.   
In response to our recommendation to broaden patient safety efforts to 
include all types of adverse events, AHRQ noted that the types of events 
vary widely and that efforts should be broadened beyond prescribed lists 
of adverse events.  AHRQ stated that it has sponsored efforts to address 
specific types of adverse events and to address causes that contribute to 
a wide variety of adverse events.  AHRQ also cited the recent 
development of its Common Formats, a set of event definitions and 
reporting forms not limited to a specific list of events designed for 
hospitals to use to report events to PSOs.    
In response to our recommendation to enhance efforts to identify 
adverse events, AHRQ stated that it intends to foster continued 
improvement in both identifying and reducing adverse events through 
operational programs, research efforts, and further collaboration with 
other agencies.  Specifically, AHRQ noted that the Common Formats 
facilitate identification of events for both internal hospital purposes and 
reporting to PSOs.  AHRQ also cited a continued commitment to its 
Patient Safety Indicators methodology as a way to identify events in 
administrative data and a planned expansion of the MPSMS program, 
which identifies adverse events in medical records acquired through 
CMS.  AHRQ plans to expand the MPSMS by broadening the areas of 
clinical investigation, seeking to address all patient populations rather 
than only Medicare beneficiaries, and working toward sharing the 
MPSMS methodology with other organizations.   
CMS.  CMS concurred with our recommendations and stated that it is 
committed to the reduction of adverse events in hospitals and other 
health care settings.  CMS provided details about current activities and 
future plans to reduce adverse events, concluding that although it has 
taken significant steps to address these issues, more work needs to be 
done.   
In response to our recommendation to broaden patient safety efforts to 
include all types of adverse events, CMS stated that it will aggressively 
pursue broadening the scope and definition of patient safety efforts to 
be more inclusive of various types of adverse events.  As an example, 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  33  
R E C O M M E N D A T I O N S  
CMS noted that it is expanding hospital reporting of quality data to 
include more measures of adverse events. 
In response to our recommendation to enhance efforts to identify 
adverse events, CMS stated that it will continue to use POA indicators 
in implementing its Medicare HAC policy.  CMS also referenced the use 
of POA indicators by QIOs to assist hospitals in reducing high-risk 
pressure ulcers and indicated that it is assessing the broader use of 
POA indicators by QIOs to assess the incidence of adverse events and 
assist hospitals in developing quality improvement plans. 
In response to our recommendation to provide further incentives for 
hospitals to reduce the incidence of adverse events through payment 
and oversight, CMS stated its commitment to more closely monitor and 
address hospital quality of care.  Specifically, CMS plans to strengthen 
the Medicare HAC policy by considering the appropriateness of 
expanding the conditions included, applying the policy to more health 
care settings, and working to improve the coding and reporting of POA 
indicators.  CMS also stated that it is working toward improving 
evaluation of the hospital conditions of participation related to patient 
safety, developing interpretive guidelines and training for surveyors, 
and tasking QIOs with greater responsibility to address adverse events 
in hospitals.  Further, CMS points to opportunities presented by the 
ACA, including implementation of the Hospital Value-Based Purchasing 
Program, which will use hospital performance as a basis for incentive 
payments; and creation of the Center for Medicare & Medicaid 
Innovation, which will address improvement in patient safety and 
reduction of adverse events.   
For the full text of AHRQ and CMS comments, see Appendix I.  We 
made minor changes to the report based on technical comments.   
 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES  34  
 A P P E N D I X   ~   A  
 
Tax Relief and Health Care Act of 2006 
P.L. No. 109-432  203 
 
DIVISION B  MEDICARE AND OTHER HEALTH PROVISIONS 
TITLE IIMEDICARE BENEFICIARY PROTECTIONS 
SEC 203 OIG STUDY OF NEVER EVENTS 
 
(a) Study. 
(1) In general.The Inspector General in the Department of Health and 
Human Services shall conduct a study on 
(A) incidences of never events for Medicare beneficiaries, including 
types of such events and payments by any party for such events; 
(B) the extent to which the Medicare program paid, denied payment, or 
recouped payment for services furnished in connection with such events 
and the extent to which beneficiaries paid for such services; and 
(C) the administrative processes of the Centers for Medicare & Medicaid 
Services to detect such events and to deny or recoup payments for 
services furnished in connection with such an event. 
(2) Conduct of study.In conducting the study under paragraph (1), the 
Inspector General 
(A) shall audit a representative sample of claims and medical records of 
Medicare beneficiaries to identify never events and any payment (or 
recouping of payment) for services furnished in connection with such 
events; 
(B) may request access to such claims and records from any Medicare 
contractor; and 
(C) shall not release individually identifiable information or facility-
specific information. 
(b) Report.Not later than 2 years after the date of the enactment of 
this Act, the Inspector General shall submit a report to Congress on the 
study conducted under this section.  Such report shall include 
recommendations for such legislation and administrative action, such as 
a noncoverage policy or denial of payments, as the Inspector General 
determines appropriate, including 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   35   
A P P E N D I X   ~   A  
(1) recommendations on processes to identify never events and to deny 
or recoup payments for services furnished in connection with such 
events; and 
(2) a recommendation on a potential process (or processes) for public 
disclosure of never events which 
(A) will ensure protection of patient privacy; and  
(B) will permit the use of the disclosed information for a root cause 
analysis to inform the public and the medical community about safety 
issues involved. 
(c) Funding. Out of any funds in the Treasury not otherwise 
appropriated, there are appropriated to the Inspector General of the 
Department of Health and Human Services $3,000,000 to carry out this 
section, to be available until January 1, 2010. 
(d) Never Events Defined.For purposes of this section, the term never 
event means an event that is listed and endorsed as a serious 
reportable event by the National Quality Forum as of  
November 16, 2006. 
 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   36   
 
 A P P E N D I X   ~   B  
 
National Quality Forum Serious Reportable Events 
 
Table B-1:  The National Quality Forum (NQF) List of Serious Reportable Events 
Surgical Events   
A.  Surgery performed on the wrong body part 
B.  Surgery performed on the wrong patient 
C.  Wrong surgical procedure performed on a patient 
D.  Unintended retention of foreign object in a patient after surgery or procedure 
E.  Intraoperative or immediately postoperative death 
Product or Device Events 
A.  Patient death or serious disability associated with use of contaminated drugs, devices, or biologics provided by the health care facility 
B.  Patient death or serious disability associated with use or function of a device in patient care in which the device is used or functions   
other than as intended 
C.  Patient death or serious disability associated with intravascular air embolism that occurs while being cared for in a health care facility 
Patient Protection Events 
A.  Infant discharged to the wrong person 
B.  Patient death or serious disability associated with patient elopement 
C.  Patient suicide, or attempted suicide resulting in serious disability, while being cared for in a health care facility 
Care Management Events 
A.  Patient death or serious disability associated with a medication error 
B.  Patient death or serious disability associated with a hemolytic reaction because of administration of incompatible blood or blood 
products 
C.  Maternal death or serious disability associated with labor or delivery in a low-risk pregnancy while cared for in a health care facility 
D.  Patient death or serious disability associated with hypoglycemia, the onset of which occurs while patient is being cared for in a health 
care facility 
E.  Death or serious disability associated with failure to identify and treat hyperbilirubinemia in neonates 
F.  Stage III or Stage IV pressure ulcers acquired after admission to a health care facility 
G.  Patient death or serious disability because of spinal manipulative therapy 
H.  Artificial insemination with the wrong donor sperm or wrong egg 
Environmental Events 
A.  Patient death or serious disability associated with an electric shock while being cared for in a health care facility 
B.  Any incident in which a line designated for oxygen or other gas to be delivered to a patient contains the wrong gas or is contaminated by 
toxic substances 
C.  Patient death or serious disability associated with a burn incurred from any source while being cared for in a health care facility 
D.  Patient death or serious disability associated with a fall while being cared for in a health care facility 
E.  Patient death or serious disability associated with the use of restraints or bedrails while being cared for in a health care facility 
Criminal Events 
A.  Care provided by someone impersonating a health care provider 
B.  Abduction of a patient of any age 
C.  Sexual assault on a patient within or on the grounds of a health care facility 
D.  Death or significant injury resulting from a physical assault that occurs within or on the grounds of the facility 
 Source:  NQF, Serious Reportable Events in Health Care 2006 Update:  Consensus Report, NQF, Washington, DC, 2007, p. 7. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   37   
 A P P E N D I X   ~   C  
Medicare Hospital-Acquired Conditions 
 
Table C-1:  Medicare Hospital-Acquired Conditions 
Conditions 
1.  Foreign object retained after surgery 
2.  Air embolism 
3.  Blood incompatibility 
4.  Pressure ulcers (stages III and IV) 
5.  Falls 
A.  Fracture 
B.  Dislocation 
C.  Intracranial injury 
D.  Crushing injury 
E.  Burn 
F.  Electric shock 
6.  Manifestations of poor glycemic control 
A.  Hypoglycemic coma 
B.  Diabetic ketoacidosis 
C.  Nonkeototic hyperosmolar coma 
D.  Secondary diabetes with ketoacidosis 
E.  Secondary diabetes with hyperosmolarity 
7.  Catheter-associated urinary tract infection 
8.  Vascular catheter-associated infection 
9.  Deep vein thrombosis/pulmonary embolism associated with the following 
A.  Total knee replacement 
B.  Hip replacement 
10.  Surgical site infection 
A.  Mediastinitis after coronary artery bypass graft  
B.  Associated with certain orthopedic procedures involving the 
a.  Spine 
b.  Neck 
c.  Shoulder 
d.  Elbow 
C.  Associated with certain bariatric surgical procedures for obesity 
a.  Laparoscopic gastric bypass 
b.  Gastroenterostomy 
c.  Laparoscopic gastric restrictive surgery 
Source:  Fiscal Year 2009 Final Inpatient Prospective Payment System Rule, 73 Fed. Reg. 48434, 48471      
(Aug. 19, 2008). 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   38   
 A P P E N D I X   ~   D  
 
Glossary of Selected Terms67 
Acute coronary syndromeCondition in which the heart does not 
receive enough oxygen-rich blood, often marked by severe chest pain, 
unstable angina, and/or heart attack. 
Acute renal insufficiencySudden loss of the kidneys ability to remove 
waste, also referred to as acute kidney failure. 
Adverse eventHarm to a patient as a result of medical care.  For 
purposes of this study, we defined adverse events as events that met at 
least one of the following criteria:  an event on the National Quality 
Forum list of Serious Reportable Events; an event on Medicares list of 
hospital-acquired conditions (HAC) for which it denies higher payment; 
or an event resulting in one of the four most serious categories on a 
patient harm index (classified on the index as F-I):  prolonged hospital 
stay, permanent harm, life-sustaining intervention, or death.  
AnticoagulantMedication that hinders blood coagulation, typically 
used to avoid blood clots and referred to as blood-thinning medication. 
AspirationAccidental inhalation of foreign material into the lungs. 
Congestive heart failureCondition in which the heart is unable to 
maintain adequate circulation of blood in the tissues of the body. 
Deep vein thrombosis (DVT)Formation of a thrombus (blood clot) 
within a deep vein (as of the leg or pelvis) that is life threatening if 
dislodgment results in blockage to the pulmonary (lung) artery. 
DeliriumMental disturbance characterized by confusion, disordered 
speech, and hallucinations. 
DialysisMedical procedure to remove wastes and toxins from the 
blood, and to adjust fluid and electrolyte imbalances. 
DysrthymiaCondition of abnormal cardiac (heart) rhythm. 
HypoglycemiaCondition of abnormally low blood sugar (glucose) level. 
HypotensionCondition of abnormally low blood pressure. 
 
67 Clinical definitions adapted from the National Institutes of Health, U.S. National 
Library of Medicine, Medline Plus Medical Dictionary, updated February 2003.  Accessed at 
http://www.nlm.nih.gov on January 7, 2009. 
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A P P E N D I X   ~   D  
Iatrogenic pneumothoraxCondition induced by therapeutic 
intervention in which air or other gas occurs in the pleural cavity. 
IleusPartial or complete obstruction of the bowel, marked by a painful 
distended abdomen, vomiting, toxemia, and dehydration. 
Intravenous (IV) infiltrateCondition in which fluids administered by 
entering a vein accidentally enter the surrounding tissue. 
Intravenous (IV) volume overloadCondition in which fluid is given by 
vein at a higher rate or larger volume than can be absorbed or excreted. 
ObstipationCondition of severe constipation (abnormally delayed 
passage of dry, hardened feces) that can result in bowel obstruction. 
Pressure ulcerUlceration of tissue deprived of adequate blood supply 
by prolonged pressure, also called decubitus ulcer and bedsore.  
Pressure ulcers are classified into four stages:  Stage I is intact skin 
with nonblanchable redness; Stage II is a shallow ulcer or blister 
indicating damage to the epidermis; Stage III is damage extending 
through all the layers of the skin; and Stage IV is damage through all 
the layers of the skin and underlying muscle, tendons, or bone.68   
Pulmonary embolismObstruction of a pulmonary (lung) artery, often 
marked by shortness of breath; chest pain with inhalation; and, in 
severe cases, low blood pressure and death. 
SepsisSystemic response to a serious, usually localized infection of 
bacterial origin, such as systemic inflammatory response syndrome. 
TachycardiaCondition of rapid heart rate. 
Temporary harm eventHarm to patient that required intervention but 
did not cause lasting harm, classified as E level on patient harm index. 
ThrushInflammation of the mouth and throat, caused by fungus. 
Urinary tract infection (UTI)Infection of the tract through which urine 
passes and can include the kidney, ureters, bladder, and/or urethra. 
Ventilator-associated pneumonia (VAP)Disease of the lungs 
characterized by inflammation of lung tissue and caused chiefly by 
infection that enters the lungs through a ventilator.
 
68 National Pressure Ulcer Advisory Panel (NPUAP), Pressure Ulcer Stages Revised by 
NPUAP.  Accessed at  http://www.npuap.org on November 12, 2009.  
 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   40   
 A P P E N D I X   ~   E  
Methodology for Identifying Events and Determining 
Preventability 
Screening for Potential Adverse Events 
We conducted a two-stage review to identify adverse events.  The first 
stage included three screening methods designed to identify 
beneficiaries who appeared likely to have experienced adverse events.  
A beneficiary was considered likely to have experienced an adverse 
event if any screening method found at least one potential adverse event 
during any of the beneficiarys hospital stays.  The screening process 
enabled us to reduce the number of cases requiring second-level review 
of the full medical records by a physician.  Additionally, physician 
reviewers indicated that the results of the screening methods helped 
them to more readily identify potential adverse events for consideration. 
The screening methods included: 
  analysis by certified medical coders of Present on Admission (POA) 
Indicators included in Medicare claims data to identify any 
diagnoses that were acquired during the hospital stay;   
  screening of medical records by nurse reviewers using a modified 
version of the Institute for Healthcare Improvements Global Trigger 
Tool (IHI GTT) for triggers that could indicate an event, such as 
laboratory test results indicating an infection; and 
  identification of any beneficiaries who were readmitted to the 
hospital within 30 days after their October 2008 hospital discharges. 
Analysis of POA Indicators.   Using data from the National Claims 
History file, certified medical coders reviewed the POA indicator data 
included in hospital Medicare claims for each sample beneficiary.  A 
recent addition required of Medicare Part A claims, the POA indicator 
codes require hospitals to make a clinical distinction about whether 
diagnoses are present at the time of admission.  The coders first verified 
the accuracy of each POA indicator by reviewing the medical records 
and then flagged each diagnosis that had a POA indicator of N (not 
present on admission), W (clinical staff unable to determine), or U 
(documentation insufficient to determine).  Analysis of POA indicators 
identified 297 beneficiaries for the second stage of the review.     
Nurse reviews of medical records.  Contracted registered nurses 
conducted a preliminary review of medical records for each sample 
beneficiary to identify potential adverse events.  Reviewers used a 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   41   
A P P E N D I X   ~   E  
modified version of the IHI GTT protocol, in which reviewers identified 
triggers in the medical records possibly indicative of adverse events and 
then explored the records further to determine whether events occurred 
and the resulting level of harm.  Medical records screening identified 
372 cases for inclusion in the second stage of review. 
Readmissions.  We identified 92 sample beneficiaries who were 
readmitted to the hospital within 30 days after their discharges in 
October 2008 and included these cases in the second stage of review.  
We reviewed records for admissions that occurred within 30 days of the 
beneficiaries last discharges; therefore, the 30-day window for 
reviewing readmissions did not span a fixed timeframe but began on the 
discharge date for each beneficiary.   
Flagged hospital stays.  We identified 420 beneficiaries for the second 
stage of review, a review of the hospital medical records by physicians.  
Of the 420 beneficiaries, we identified 391 with the 3 screening methods 
and 29 from additional analysis.  In the 29 additional cases, the 
beneficiaries were not flagged on the 3 screening methods, but staff 
involved in the screening process (nurses, coders, or analysts) believed 
complexities in the cases warranted physician review.   
Identifying Events Within Flagged Cases 
Five contracted physicians conducted medical records review of the  
420 cases identified by the screening methods.  Physician reviewers 
represented a variety of specializations and experience:  an infectious 
disease specialist, a cardiologist, an orthopedic surgeon, an intensivist 
(intensive care specialist), and an internist.  All five had many years of 
clinical experience, as well as prior experience in detecting adverse 
events in medical records.  Three of the five served as physician 
reviewers for a 2008 Office of Inspector General (OIG) case study.69 
Over 12 weeks, the physician reviewers examined hospital medical 
records for each of the 420 cases.70  Physician reviewers used a 
structured medical review protocol that required them to describe each 
adverse event; identify the medical record documentation that led to 
 
69 OIG, Adverse Events in Hospitals:  Case Study of Incidence Among Medicare 
Beneficiaries in Two Counties, OEI-06-08-00220, December 2008.   
70 These included medical records for all hospital stays for sample beneficiaries ending with 
October 2008 discharges.  Additionally, physicians reviewed records for any readmissions of 
sample beneficiaries that occurred within 30 days after their final October discharges to look 
for evidence of events that occurred during the October 2008-discharged stays. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   42   
A P P E N D I X   ~   E  
 
their identification of the event; and specify the level of harm 
experienced by the patient, with harm categorized in accordance with 
the National Coordination Council for Medication Errors Reporting and 
Prevention Index of Categorizing Medication Errors. 
Throughout our study preparation, medical records review, and 
analysis, we facilitated 22 weekly conference calls during which the 
physician reviewers discussed the review protocol and sample cases that 
either were complex or had possible implications for other cases.  These 
calls assisted in making determinations for difficult cases and helped 
achieve consistency across reviewers.  The physicians determined that 
the following types of cases would require group discussion:  events 
assessed as clearly preventable; events contributing to death; and cases 
involving respiratory failure, hypoglycemia, hypotension, urinary tract 
infections, and complex and/or lengthy surgeries.  Physicians also often 
brought cases to group discussion if they involved care specific to a 
specialization of another physician.  We documented the discussions and 
conclusions made during these weekly calls, continually revising a 
written physician guidance document to further promote consistency.  
The physicians discussed 162 of the 302 events (54 percent) and other 
cases that the group ultimately determined did not include events.       
Determining Preventability for Each Event 
As part of the structured medical review protocol, reviewers also 
assessed the likelihood that the events were preventable.  In 
collaboration with the physicians, we created an initial response scale:   
 PreventablePatient harm could have been avoided through 
improved assessment or alternative actions. 
 Not preventablePatient harm could not have been avoided given the 
complexity of the patients condition or the care required.  
 Unable to determinePhysicians were unable to determine 
preventability because of incomplete documentation or case 
complexity.  
Through the pretest process, we expanded the scale to enable physicians 
to more precisely gauge the extent to which an event was preventable.  
The expanded scale divided the preventable and nonpreventable 
responses with the descriptors clearly and likely.  Assessing an event as 
clearly preventable or clearly not preventable required a greater degree 
of certainty on the part of the reviewer.  The expanded scale enabled 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   43   
AA PP PP EE NN DD II XX    ~~    EE   
 
physicians to make more precise determinations, while our primary 
statistics continued to collapse clearly and likely.  
To make distinctions about the circumstances in each case, physicians 
used their clinical experience and judgment.  They considered all 
evidence in the medical records, including staff actions and the patients 
condition.  Physicians also used information about accepted standards of 
care, the frequency with which certain events occurred despite 
appropriate assessment and care, the physicians individual clinical 
experiences, guidance developed during the review process, and group 
discussion of cases.  Using a list of contributing factors gleaned from 
prior research, physicians indicated the rationale for each 
determination and provided a narrative description for each case. 
To improve consistency, physician reviewers used a uniform method for 
reviewing preventability.  Reviewers developed a decision algorithm 
during practice reviews consisting of a series of questions that led the 
reviewers to a suggested response.  Questions addressed issues such as 
whether there was a medical error, whether the event could have been 
anticipated, and how frequently the event occurred given proper care.  
Physicians did not automatically accept the suggested response, but 
assessed whether it was appropriate for each case.  In completing the 
rationale section of the protocol, physicians assessed contributing 
factors.  The list of contributing factors included broad concepts from 
the decision algorithm, such as errors, and more nuanced factors, such 
as whether the patient was monitored or was susceptible to the event.  
We required that physicians discuss all clearly preventable 
determinations during group meetings (as they required greater 
certainty), and encouraged them to bring other cases for discussion if 
they had difficulty or felt the cases would inform other determinations.  
Figure E-1 illustrates the preventability review process. 
Physician Review of Findings 
Following the medical records review, we analyzed the identified events, 
harm levels, and preventability determinations to identify any 
inconsistencies and discussed these with the full physician group.  This 
process resulted in some changes to the initial determinations, such as 
collapsing a series of events into a single cascade event.71        
 
71 Based on OIG interviews with IHI staff, IHI defines a cascade event as one in which an 
initial event causes a series of related events for the same patient and advocates collapsing 
these into a single event.    
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   44   
A P P E N D I X   ~   E  
 
Figure E-1:  Physician Review Process for Determining Preventability  
  Part I Decision Algorithm To Determine Suggested Response 
 
Q1: Was an identifiable error or 
Yes
  system failure documented in the  Clearly or likely preventable
medical record?
 
No
 
  Q2: Could the care provider have 
No
anticipated this event with the  Clearly or likely not preventable
  information available at the time?
 
Yes
Yes
  Clearly or likely not preventable
Q3: Were appropriate precautions 
 
taken to prevent this event? 
No
Clearly or likely preventable
 
Unable to determine
 
Rarely
Q4: How frequently does this type  Clearly or likely preventable
  of adverse event occur when proper 
preparation and procedures are in 
  Occasionally
place? Clearly or likely not preventable
 
Part II Rationale List To Evaluate Suggested Response
 
Consider the rationale list for the suggested response: 
 
Preventable Not Preventable
  medical error proper procedures followed
substandard treatment patient highly susceptible
  inadequate monitoring could not have anticipated
inadequate assessment patient's condition complex
 
necessary treatment not provided
event rarely happens Unable To Determine
  poor communication poor or absent documentation
flawed safety systems medical care complex
  breakdown in environment patient's condition complex
 
Yes
Make selection in protocol
 
Do you feel confident that the 
  suggested response is appropriate?
No
Request group discussion
 
Source:  OIG illustration of physician medical record review process for determining preventability. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   45   
 A P P E N D I X   ~   F  
Estimates, Confidence Intervals, and Key Statistics  
We computed incidence rates and corresponding 95-percent confidence 
intervals using the computer program Sudaan.  Sudaan is a statistical 
analysis program with appropriate standard statistical formulas for 
calculating correct standard errors for complex sampling designs.   
Table F-1:  Estimates, Confidence Intervals, and Key Statistics  
95-Percent  95-Percent 
Confidence  Confidence 
  Estimated  Interval  Estimated  Interval 
Percentage of  Lower  Upper  Number of  Lower  Upper 
n  Beneficiaries  Bound Bound Beneficiaries  Bound  Bound 
Event Experiences for All Beneficiaries (n=780)  
Experienced adverse events  105  13.46% 11.24% 16.05% 133,710  111,644  159,421 
  National Quality Forum Serious 
Reportable Events*  5  0.64% 0.27% 1.53% 6,367  2,682  15,197 
  Medicare hospital-acquired 
conditions*  8  1.03% 0.51% 2.04% 10,187  5,066  20,263 
  F-I level adverse events  102  13.08% 10.88% 15.63% 129,890  108,069  155,249 
  Events that overlap at least two 
categories*  9  1.15% 0.60% 2.20% 11,461  5,960  21,852 
  Events that overlap all three 
categories*  1  0.13% 0.02% 0.91% 1,273  199  9,039 
Experienced temporary harm 
events  105  13.46% 11.24% 16.05% 133,710  111,644  159,421 
Experienced only preventable 
adverse events  58  7.44% 5.79% 9.50% 73,859  57,511  94,361 
Experienced only preventable 
temporary harm events  49  6.28% 4.78% 8.22% 62,398  47,479  81,647 
Experienced adverse events that 
contributed to death*  12  1.54% 0.87% 2.69% 15,281  8,642  26,719 
Beneficiaries Who Experienced at Least One Adverse Event (n=105) 
Experienced multiple adverse 
events  19  18.10% 11.84%  26.66% 24,195  15,831  35,647 
Experienced temporary harm in 
addition to adverse events  29  27.62% 19.91%  36.94% 36,929  26,622  49,392 
Experienced cascade events  28  26.67% 19.08%  35.93% 35,656  25,512  48,042 
Beneficiaries Who Experienced at Least One Temporary Harm Event (excluding those who experienced adverse 
events) (n=105) 
Experienced multiple temporary 
harm events  23  21.90% 15.00%  30.83% 29,289  20,057  41,223 
Beneficiaries Who Experienced Events and Were Covered Under the Inpatient Prospective Payment System (IPPS) 
(n=171) 
Incurred additional costs  28  16.37% 11.54%  22.71% 35,656  25,129  49,453 
Did not incur additional costs  143  83.63% 77.29%  88.46% 182,101  168,304  192,628 
 
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision.
Source:  Office of Inspector General (OIG) analysis of hospital stays and Medicare claims for 780 Medicare beneficiaries discharged in        
October 2008. 
 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   46   
A P P E N D I X   ~   F  
 
 
Table F-2:  Estimates, Confidence Intervals, and Key Statistics  
95-Percent Confidence Interval 
  n  Percentage Estimate  Lower Bound  Upper Bound 
Preventability Classification for All Adverse Events and Temporary Harm Events (n=302) 
All adverse and temporary harm events  302 100% NA N A
  Preventable events   133  44.04% 38.06%  50.19%
o Clearly preventable events  28  9.27% 6.53%  13.01%
o Likely preventable events  105  34.77% 29.20%  40.79%
  Not preventable events  155  51.32% 45.22%  57.39%
o Clearly not preventable events  55  18.21% 13.92%  23.47%
o Likely not preventable events  100  33.11% 27.59%  39.14%
  Unable to determine*  14  4.64% 2.80%  7.59%
Clinical Category for All Adverse Events (n=128)  
All clinical categories  128  100%  NA  NA 
  Medication  40 31.25% 23.35%  40.41%
  Patient care  36  28.13%  20.92%  36.66% 
  Surgery and other procedures  33  25.78%  18.77%  34.31% 
  Infection  19  14.84%  9.64%  22.18% 
Clinical Category for All Temporary Harm Events (n=174)  
All clinical categories  174 100%  NA  NA 
  Medication   73 41.95%  34.74%  49.53%
  Patient care  63 36.21%  29.09%  43.98%
  Surgery and other procedures  32 18.39%  12.92%  25.50%
  Infection  6 3.45%  1.58%  7.36%
Harm Level for All National Coordinating Council Medication Errors Reporting and Prevention Index for Categorizing 
 
Errors F-I Level Events (n=122)**
All NCC MERP harm levels  122 100%  NA  NA 
  Harm F  76 62.30%  53.42%  70.41%
  Harm G*  6 4.92%  2.22%  10.54%
  Harm H  28 22.95%  16.15%  31.54%
  Harm I*  12 9.84%  5.75%  16.33%
Preventable Adverse and Temporary Harm Events Within Each Clinical Category  
  Infection (n=25)  15 60.00%  39.72%  77.35%
  Medication (n=113)  57 50.44%  40.98%  59.87% 
  Patient care (n=99)  50 50.51%  40.47%  60.50%
  Surgery and other procedures (n=65)  11 16.92%  9.51%  28.30%
continued on next page 
 
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision. 
** National Coordinating Council for Medication Errors Reporting and Prevention Index for Categorizing Errors (NCC MERP). 
 
 
 
 
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Table F-2:  Estimates, Confidence Intervals, and Key Statistics (Continued) 
95-Percent  Confidence Interval 
  n  Percentage Estimate  Lower Bound  Upper Bound 
Physician Rationale for All Preventable Events (n=133) 
Error related to medical judgment, skill, or 
patient management   77  57.89%  49.04%  66.27%
Appropriate treatment was provided in a 
substandard way  61  45.86%  37.64%  54.33%
Patients progress was not adequately 
monitored  50  37.59%  29.76%  46.14%
Patients health status was not adequately 
assessed  30  22.56%  15.87%  31.02%
Necessary treatments were not provided  22  16.54%  11.10%  23.92%
Event rarely happens when proper 
precautions and procedures are followed  18  13.53%  8.46%  20.95%
Poor communication between caregivers*  10  7.52%  3.86%  14.14%
Facilitys patient safety systems and policies 
were inadequate or flawed*  4  3.01%  1.12%  7.81%
Breakdown in hospital environment 
occurred (equipment failure, etc.)*  2  1.50%  0.38%  5.80%
 
Physician Rationale for All Nonpreventable Events (n=155)
Event occurred despite proper assessment 
and procedures followed  96  61.94%  52.82%  70.28%
Patient was highly susceptible to event 
because of health status   77  49.68%  41.34%  58.04%
Care provider could not have anticipated 
event given information available  54  34.84%  27.54%  42.92%
Patients diagnosis was unusual or complex, 
making care difficult  45  29.03%  21.67%  37.70%
Harm was anticipated but was considered 
acceptable given alternatives*    21  13.55%  8.75%  20.40%
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision. 
 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries discharged in October 2008.
Table F-3:  Statistical Test Results for Preventability Subanalysis  
P-Value for 
  Difference 
Statistical Test  in Proportions 
Test for relationship among preventability determinations and harm events (i.e., adverse event or 
temporary harm event)  0.0568 
Test for relationship between preventability determinations and clinical categories (e.g., surgical event, 
medication event, patient care event, or infection)  <0.0001* 
Test for difference between preventability determinations  
  Surgical events versus infection events 
 0.0013* 
  Surgical events versus medication events  <0.0001* 
  Surgical events versus patient care events  <0.0001* 
Test for difference of means between average additional costs incurred by entire stays and average 
additional costs attributed to events within the initial hospital stays  0.0104* 
Note:  Weighted chi square and Cochran-Mantel-Haenszel chi square produced similar results.   
* P-values are statistically significant at the 95 precent confidence level.  
Source:  OIG analysis of hospital stays and Medicare claims for 780 Medicare beneficiaries discharged in October 2008. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   48   
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Table F-4:  Projections and Confidence Intervals for Analysis of Medicare Costs 
Associated With Adverse Events and Temporary Harm Events  
 
95-Percent Confidence Interval 
 
Projected  Projected 
 
Population  Cost Estimate  Lower Bound  Upper Bound 
Medicare Inpatient Costs for Projected Population (n=657) 
Estimate of Medicare inpatient costs  836,646  $9,167,576,966  $8,505,456,013  $9,829,697,918 
Medicare Inpatient Costs for Projected Population Associated With Adverse and Temporary Harm Events (n=657) 
Costs associated with all events  836,646  $324,155,814  $161,745,099  $486,566,529 
Costs associated with preventable events  836,646  $118,720,272  $33,915,875  $203,524,670 
Source:  OIG analysis of hospital stays and Medicare claims for 780 Medicare beneficiaries discharged in October 2008. 
 
* Medicare costs are calculated based on the 657 sample cases in the IPPS.
 
Table F-5:  Projections and Confidence Intervals for Average Additional Medicare Costs 
Associated With Adverse Events and Temporary Harm Events 
Projected 
95-Percent Confidence Interval 
Average  
Events Resulting in Increased Medicare Costs  Additional Cost  Lower Bound  Upper Bound 
Events resulting in increased costs for additional hospital 
stays (n=12)  $13,745  $7,760  $19,730 
Events resulting in increased costs for initial hospital 
stays (n=16)  $5,601  $3,889  $7,313 
Source:  OIG analysis of hospital stays and Medicare claims for 780 Medicare beneficiaries discharged in October 2008. 
 
Table F-6:  Percentage Estimates and Confidence Intervals for Medicare Costs 
Associated With Adverse Events and Temporary Harm Events 
95-Percent Confidence Interval 
  Percentage 
Estimate   Lower Bound  Upper Bound 
Percentage of Total Medicare IPPS Costs 
All adverse and temporary harm events  3.54% 1.82%  5.26%
Preventable adverse and temporary harm events  1.30%* 0.38%  2.21%
Percentage of Medicare IPPS Costs Attributed to Adverse Events and Temporary Harm Events 
Associated with adverse events  87.48% 73.70%  100.00%
Associated with temporary harm events  14.93%* 0.34%  29.52%
Associated with entire additional hospital stays  64.80% 43.82%  85.77%
. 
*Given the small proportions, confidence intervals for projected numbers exceed 50-percent relative precision
Source:  OIG analysis of hospital stays and Medicare claims for 780 Medicare beneficiaries discharged in October 2008. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   49   
 A P P E N D I X   ~   G    
Rates of Adverse Events and Temporary Harm Events by Patient 
Days and Hospital Admissions 
Hospitals commonly measure adverse events by incidence density, 
which takes into account the period during which patients are observed.  
For example, incidence density is often used in measuring hospital-
acquired infections because risk can increase with the length of 
exposure to the health care environment.72  The Institute for Healthcare 
Improvement (IHI), a nonprofit advisory group to hospitals, cites 
advantages to using incidence density metrics over standard incidence 
rates that measure the number of events per patient.73  IHI reports that 
measuring total events by patient days or hospital admissions enables 
hospitals to count multiple events experienced by the same beneficiary.   
The sample of 780 Medicare beneficiaries discharged during        
October 2008 included 838 total hospital stays (admissions) and a total 
of 4,354 days in the hospital (patient days).  We calculated patient days 
by subtracting the admission date for each hospital stay from its 
discharge date.74  Table G-1 provides ratios for adverse events and 
temporary harm events in the sample per 1,000 patient days and        
per 100 admissions. 
Table G-1:  Rates of Adverse and Temporary Harm Events in 
the Sample by Patient Days and Hospital Admissions 
Per 1,000  Per 100 
Category 
Patient-Days  Admissions 
Adverse events  29  15 
Temporary harm events  40  21 
Adverse events and temporary harm events combined  69  36 
Source:  Office of Inspector General analysis of hospital stays for 780 Medicare beneficiaries in          
October 2008. 
 
72 K.M. Arias, Outbreak Investigation, Prevention, and Control in Health Care Settings, 
Second Edition, 2009, Jones and Bartlett Publishers, pp. 330331. 
73 IHI, IHI Global Trigger Tool for Measuring Adverse Events, Second Edition, 2009, p. 13. 
74 In consultation with physician reviewers, we excluded the seven patients admitted and 
discharged on the same day (these patients did not experience temporary harm or adverse 
events).  IHI recommends selecting patient records for only hospital stays of at least 24 hours.   
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   A P P E N D I X   ~   H  
Adverse Events and Temporary Harm Events 
Tables H-1 and H-2 contain information about adverse events and 
temporary harm events identified in the sample, including National 
Quality Forum (NQF) Serious Reportable Events and Medicare 
hospital-acquired conditions (HAC).  Table H-1 contains information 
about adverse events (128 adverse events).75  Table H-2 contains 
information about temporary harm events (174 events).  The event 
descriptions vary somewhat depending upon the language the physician 
reviewers used to describe the event and the level of detail included in 
their notes. 
 
Table H-1:  Adverse Events by Clinical Category, Harm Level, Preventability, and 
Whether the Events Were NQF Serious Reportable Events or Medicare HACs (n=128) 
Harm 
Adverse Event  Preventability  NQF   HAC 
Level 
Events Related to Medication (40) 
Excessive bleeding (12) 
1. Abdominal bleeding secondary to anticoagulant given for deep 
I  CNP     
vein thrombosis (enoxaparin)  
2. Brain hemorrhage secondary to anticoagulants (aspirin and 
F  CNP     
clopidogrel) 
3. Cascade event in which delay in care and administration of aspirin 
I  CP     
to patient with low platelet count led to pulmonary hemorrhage  
4. Cascade event in which gastrointestinal bleeding and hematoma 
associated with aspirin and anticoagulant (clopidogrel) given  I  CNP     
following coronary stent placement resulted in acute blood loss 
5. Hematuria secondary to anticoagulant (warfarin)   F  LP     
6. Retroperitoneal hemorrhage secondary to anticoagulant (warfarin)   I  CP     
7. Gastrointestinal bleeding secondary to anticoagulant (enoxaparin)   I  CNP     
8. Gastrointestinal bleeding secondary to anticoagulant (warfarin)   F  LP     
9. Gastrointestinal bleeding secondary to anticoagulants (aspirin, 
F  CNP     
clopidogrel, and enoxaparin)  
10. Gastrointestinal bleeding secondary to anticoagulants (aspirin, 
F  CNP     
clopidogrel, and eptifibatide)  
11. Gross hematuria secondary to anticoagulants (aspirin and 
F  LNP     
clopidogrel) 
12. Hematoma secondary to anticoagulant (heparin)   F  LP     
 
continued on next page 
 
75 The harm level is classified according to the National Coordinating Council for 
Medication Errors Reporting and Prevention (NCC MERP) Index for Categorizing Errors    
(EI).  Preventability determination is reflective of the physician review index:  CP = clearly 
preventable, LP = likely preventable, LNP = likely not preventable, CNP = clearly not 
preventable, and UTD = unable to determine. 
 
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Table H-1:  Adverse Events by Clinical Category, Harm Level, Preventability, and 
Whether the Events Were NQF Serious Reportable Events or Medicare HACs  
(n=128) (Continued) 
Harm 
Adverse Event  Preventability  NQF  HAC 
Level 
Events Related to Medication (continued) 
Delirium or change in mental status (7) 
1. Cascade event in which narcotic analgesic (hydromorphone) 
induced delirium, which led to use of physical restraints, patient  F  CP     
pulling out IVs, and patient fall  
2. Cascade event in which narcotic analgesic (oxycodone) induced 
F  CP     
delirium and resulted in patient fall  
3. Confusion secondary to narcotic analgesics (dextropropoxyphene 
F  CP     
with acetaminophen)  
4. Delirium secondary to sedative (benzodiazepine)  F  CNP     
5. Hallucinations and delirium secondary to antiwithdrawal medication 
F  CNP     
(naloxone)  
6. Hallucinations and delirium secondary to narcotic analgesic 
F  LP     
(hydromorphone)  
7. Mental status change due to narcotic analgesic (morphine)  F  CP     
Hypoglycemic event (6) 
1. Episode of severe hypoglycemia secondary to insulin management   H  LNP     
2. Hypoglycemic coma secondary to insulin management  H  LP     
3. Hypoglycemic coma secondary to insulin management   I  LP     
4. Hypoglycemic coma and permanent brain injury secondary to 
insulin management in patient with anoxic encephalopathy  G  CP     
following cardiac arrest 
5. Multiple episodes of severe hypoglycemia secondary to insulin 
H  CP     
management 
6. Recurrent hypoglycemia secondary to diabetes medication 
F  CP     
(glipizide) 
Acute renal insufficiency (kidney failure) (4) 
1. Acute renal failure secondary to antihypertensives and diuretics 
F  LNP     
(unspecified) 
2. Acute renal failure secondary to blood pressure medication 
F  LP     
(enalapril) 
3. Acute renal failure and permanent decrease of renal function 
G  LP     
secondary to dehydration from diuretic (furosemide) 
4. Severe acute renal insufficiency and dehydration secondary to 
F  LNP     
diuretics (bumetanide and spironolactone) 
Severe hypotension (4) 
1. Hypotension secondary to narcotic analgesic (hydromorphone)  F  LP     
2. Hypotension secondary to diuretics (unspecified)  F  LP     
3. Hypotension secondary to multiple psychiatric medications 
F  LP     
(mirtazapine, risperidone, and sertraline) 
4. Hypotension secondary to multiple sedatives (ketamine, 
H  CNP     
lorazepam, and propofol) 
Respiratory complication (4) 
1. Acute hypercarbic respiratory failure (excess oxygen)   H  LP     
2. Cascade event in which narcotic analgesic (hydromorphone) led to 
H  LP     
respiratory failure and recurrent somnolence  
3. Respiratory depression secondary to antianxiety medication 
H  LP     
(lorazepam) and narcotic analgesic (morphine)  
4. Respiratory failure secondary to sedative (benzodiazepine)   I  CP     
Severe allergic reaction (3) 
1. Failure to diagnose Stevens-Johnson Syndrome secondary to 
F  LP     
anticonvulsants (carbamazepine and phenytoin) 
2. Hives and shortness of breath due to allergic reaction to antibiotic  F  CNP     
3. Throat swelling due to allergic reaction to blood transfusion  H  CNP     
 continued on next page 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   52   
   A P P E N D I X   ~   H  
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WWhheetthheerr  tthhee  EEvveennttss  WWeerree  NNQQFF  SSeerriioouuss  RReeppoorrttaabbllee  EEvveennttss  oorr  MMeeddiiccaarree  HHAACCss          
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Harm 
Adverse Event  Preventability  NQF  HAC 
Level 
Events Related to Patient Care (36) 
Intravenous (IV) volume overload (10) 
1. Cascade event in which cessation of diuretic (furosemide) and 
H  LP     
administration of excess saline led to acute pulmonary edema  
2. Cascade event in which IV volume overload led to mild congestive 
heart failure and subsequent treatment with diuretic (furosemide) led  F  LNP     
to hypokalemia 
3. Hypoxic respiratory failure secondary to IV volume overload   H  LNP     
4. Hypoxic respiratory failure secondary to IV volume overload   H  LP     
5. IV volume overload with associated leg edema and complicated by 
F  LNP     
preexisting pneumonia 
6. Pleural effusions and intermittent dyspnea secondary to IV volume 
F  LNP     
overload  
7. Pulmonary edema and effusions secondary to IV volume overload   F  CNP     
8. Pulmonary edema and respiratory distress secondary to IV volume 
H  LP     
overload  
9. Respiratory failure secondary to IV volume overload  H  LP     
10. Respiratory insufficiency and reintubation secondary to IV volume 
F  LNP     
overload 
Aspiration (8) 
1. Aspiration associated with feeding tube placement   F  LP     
2. Aspiration pneumonia associated with food intake  I  UTD     
3. Aspiration pneumonia associated with unspecified infiltrate   F  LP     
4. Aspiration pneumonia associated with unspecified infiltrate   F  LNP     
5. Aspiration pneumonitis associated with unspecified infiltrate   F  LP     
6. Cascade event in which aspiration led to respiratory failure, acute 
I  UTD     
renal failure, shock, and cardiac arrest  
7. Cascade event in which recurrent aspiration led to infection   F  LP     
8. Cascade event in which episode of vomiting led to aspiration 
F  LNP     
pneumonia in patient with congestive heart failure 
Venous thrombosis or pulmonary embolism (5)    
1. Bilateral deep venous thrombosis  F  LP     
2. Bilateral pulmonary emboli  F  LP     
3. Deep venous thrombosis secondary to central catheter  F  UTD     
4. Multiple pulmonary emboli (right pulmonary artery)  F  LP     
5. Venous thrombosis (saphenous vein)  F  LNP     
Exacerbation of preexisting medical condition (5) 
1. Cascade event in which failure to diagnose hypotension and septic 
H  CP     
shock led to severe hypotension 
2. Cascade event in which failure to diagnose postoperative bowel 
distension led to toxic megacolon, bowel perforation, abdominal  H  UTD     
sepsis, and shock  
3. Progressive respiratory difficulties resulting from failure to complete 
F  LP     
congestive heart failure therapy 
4. Progressive respiratory difficulties resulting from failure to diagnose 
F  LP     
hemothorax  
5. Progressive respiratory difficulties resulting from failure to diagnose 
F  CP     
pulmonary infiltrate and pneumonia  
Stage III pressure ulcer (3) 
1. Progression from single stage II pressure ulcer to bilateral stage III 
E  LP     
pressure ulcers (buttocks) 
2. Progression from stage I pressure ulcer to stage III pressure ulcer 
E  LP     
(heel)  
3. Stage III pressure ulcer (sacrum)  E  LP     
 
continued on next page 
 
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Table H-1:  Adverse Events by Clinical Category, Harm Level, Preventability, and 
Whether the Events Were NQF Serious Reportable Events or Medicare HACs  
(n=128) (Continued)  
Harm 
Adverse Event  Preventability  NQF  HAC 
Level 
Events Related to Patient Care (continued) 
Other events related to patient care (5) 
1. Breakdown of surgical wound   F  UTD     
2. Congestive heart failure resulting from failure to manage high blood 
F  LNP     
pressure 
3. Hypoxia resulting from failure to stabilize tracheostomy and provide 
H  CP     
oxygen during transfer 
4. Severe back pain and possible vertebral compression fracture from 
F  CNP     
patient fall 
5. Significant episode of weakness and dizziness associated with an 
F  LP     
exacerbation of hyponatremia 
Events Related to Surgery or Other Procedures (33) 
Excessive bleeding (5) 
1. Bleeding for several days following colonoscopy   F  LNP     
2. Bleeding from femoral artery following IV placement   F  LNP     
3. Cascade event in which hemorrhage of femoral artery at puncture 
H  LP     
site led to shock, apnea, and ultimately a myocardial infarction  
4. Cascade event in which premature removal of dialysis needle 
H  CP     
resulted in excessive bleeding, shock, intubation, and aspiration  
5. Hematoma following knee arthroplasty   F  LP     
Severe hypotension (4) 
1. Hypotension during hemodialysis treatment   F  LNP     
2. Hypotension following cardiac surgery  F  LNP     
3. Hypotension following endoscopic procedure   H  CNP     
4. Hypotension with atrial fibrillation and rapid ventricular response 
F  LP     
following dialysis treatment 
Respiratory complication (4) 
1. Agonal breathing following premature extubation    H  CP     
2. Cascade event in which acute respiratory failure following 
F  LNP     
cardiac procedure led to hematuria and hemoptysis 
3. Cascade event in which angioedema secondary to contrast 
used for fistulogram led to intubation, ventilator-associated  I  CNP     
pneumonia, and shock  
4. Respiratory distress following percutaneous tracheostomy    H  CNP     
Iatrogenic pneumothorax (3)   
1. Cascade event in which postoperative pneumothorax led to acute 
H  LNP     
respiratory failure  
2. Cascade event in which removal of chest tube led to pneumothorax, 
H  LNP     
reinsertion of chest tube, and reintubation  
3. Pneumothorax following chest tube placement   F  CNP     
Postoperative ileus (3)         
1. Cascade event in which outpatient surgery to repair hernia following 
cholecystectomy led to hospitalization for postoperative hypoxemia,  F  LNP     
atelectasis, and ileus 
2. Significant ileus following partial colon resection   F  CNP     
3. Significant ileus following partial colon resection   F  LNP     
 
continued on next page 
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Table H-1:  Adverse Events by Clinical Category, Harm Level, Preventability, and 
Whether the Events Were NQF Serious Reportable Events or Medicare HACs  
(n=128) (Continued) 
Harm 
Adverse Event  Preventability  NQF  HAC 
Level 
Events Related to Surgery or Other Procedures (continued) 
Postoperative urinary retention (3) 
1. Postoperative urinary retention associated with indwelling urinary 
F  LNP     
catheter   
2. Postoperative urinary retention associated with indwelling urinary 
F  LP     
catheter  
3. Postoperative urinary retention associated with urinary catheter   F  LNP     
Acute coronary syndrome (2)  
1. Acute coronary syndrome following laparoscopic cholecystectomy 
G   CNP     
and resulting in permanent damage to heart muscle 
2. Acute coronary syndrome that developed as a complication of 
F  CNP     
percutaneous coronary intervention  
Blood clots and other occlusions (blockage within a blood vessel) (2) 
1. Acute occlusion of the popliteal artery following colonoscopy and 
G  CNP     
partial colon resection  
2. Pericardial blood clot following cardiac surgery   F  LNP     
Cardiac complication (2) 
1. Atrial fibrillation following mitral valve replacement surgery   H  CNP     
2. Severe ventricular tachycardia following coronary artery bypass 
H  CNP     
graft 
Other procedure-related complication (5) 
1. Cascade event in which coronary bypass surgery led to complex 
H  LNP     
tachycardia complicated by hypotension 
2. Cascade event in which complications following bowel surgery 
F  LNP     
resulted in surgical site hemorrhage   
3. Delay in surgery because of equipment malfunction  F  LP     
4. Hematuria due to indwelling urinary catheter-associated trauma   F  LNP    
5. Seroma (pocket of fluid) following stomach resection   F  LNP    
Events Related to Infection (19) 
Urinary tract infection (5) 
1. Cascade event in which cystoscopy eroded artificial urethral 
sphincter necessitating use of urinary catheter which led to urinary  G  LP     
tract infection (E. coli)  
2. Urinary tract infection (E. coli) associated with urinary catheter   F  LP     
3. Urinary tract infection (E. coli) associated with urinary catheter   E  LP     
4. Urinary tract infection (Klebsiella) associated with urinary catheter   E  LP     
5. Urinary tract infection (Serratia) associated with urinary catheter   E  LP     
Vascular catheter-associated infection (central or peripheral line) (4) 
1. Cascade event in which vascular catheter led to sepsis, deep vein  F  LP     
thrombosis, and pulmonary embolism  
2. Cascade event in which vascular catheter led to septicemia and  F  LP     
deep vein thrombosis  
3. Forearm cellulitis (inflammation of skin or connective tissue) 
F  CP     
following vascular catheter insertion  
4. Methicillin-resistant Staphylococcus aureus (MRSA) infection 
H  LP     
following pleural catheter insertion  
 
continued on next page 
 
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Table H-1:  Adverse Events by Clinical Category, Harm Level, Preventability, and 
Whether the Events Were NQF Serious Reportable Events or Medicare HACs   
(n=128) (Continued) 
Harm 
Adverse Event  Preventability  NQF  HAC 
Level 
Events Related to Infection (continued) 
Other bloodstream infections (excluding vascular catheter-associated  
Infections) (4) 
1. Cascade event in which failure to treat systemic inflammatory 
response syndrome led to acute renal failure and aspiration  I  CP     
pneumonia  
2. Cascade event in which removal of urinary catheter led to 
recurrence of obstructive uropathy, renal failure, sepsis, and  G  CP     
permanent deterioration of renal function 
3. Cascade event in which untreated febrile neutropenia led to septic 
I  CP     
shock  
4. Sepsis (methicillin-resistant Staphylococcus epidermis)   F  LNP     
Respiratory infection (4) 
1. Pneumonia (MRSA) following abdominal surgery   F  LNP     
2. Pneumonia (unspecified) following knee surgery   F  LNP     
3. Ventilator-associated pneumonia (Klebsiella)  F  LNP     
4. Ventilator-associated pneumonia (MRSA)   H  LNP     
Surgical or procedural site infection (2) 
1. Cascade event in which anastomotic leak following colectomy led to 
F  LP     
abscesses and bacteremia  
2. Surgical site infection following foot surgery   F  LNP     
Source:  Office of Inspector General (OIG) analysis of hospital stays for 780 Medicare beneficiaries in October 2008. 
 
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Table H-2:  Temporary Harm Events, E Level on the NCC MERP Index, Identified 
Among Medicare Beneficiaries by Clinical Category (n=174 )  
Temporary Harm Event  Preventability 
Events Related to Medication (73) 
Delirium or change in mental status (22) 
1. Altered mental status secondary to narcotic analgesic (fentanyl) and sedative 
LP 
(midazolam) 
2. Cascade event in which delirium secondary to antipsychotic (haloperidol) led to patient 
LP 
pulling catheter out which resulted in hematuria  
3. Confusion and delirium secondary to narcotic analgesics (hydromorphone and 
LP 
morphine)  
4. Confusion secondary to narcotic analgesic (hydromorphone)   LP 
5. Confusion secondary to sedative (benzodiazepine)  LP 
6. Delirium secondary to anticonvulsants (valproic acid)  CNP 
7. Delirium secondary to local anesthetic (lidocaine)  CNP 
8. Delirium secondary to narcotic analgesic (hydromorphone)   LP 
9. Delirium secondary to narcotic analgesic (hydrocodone with acetaminophen)  LP 
10. Delirium secondary to narcotic analgesic (morphine)   CNP 
11. Drowsiness secondary to narcotic analgesic (hydromorphone)  LNP 
12. Hallucinations and delirium secondary to narcotic analgesic (morphine)   LNP 
13. Hallucinations secondary to sedative (alprazolam) and multiple narcotic analgesics   UTD 
14. Lethargy secondary to narcotic analgesic (hydromorphone)   LP 
15. Lethargy secondary to narcotic analgesic (oxycodone with acetaminophen)   LP 
16. Omission of antidepressant (fluoxetine with olanzapine) that led to episode of acute 
LP 
paranoia  
17. Oversedation secondary to antihistamine and sedative (promethazine)  LP 
18. Oversedation secondary to multiple psychiatric medications (alprazolam, haloperidol, 
LNP 
and quetiapine) 
19. Oversedation secondary to narcotic analgesic (fentanyl) and sedative (midazolam)  LNP 
20. Oversedation secondary to narcotic analgesic (hydromorphone)   LP 
21. Paranoid delusions secondary to narcotic analgesics (hydromorphone and morphine)  LP 
22. Somnolence secondary to narcotic analgesics (hydromorphone and morphine)  CP 
Hypoglycemic event (11) 
1. Hypoglycemia secondary to diabetes medication (glipizide)  UTD 
2. Hypoglycemia secondary to glycemic management  CP 
3. Hypoglycemia secondary to glycemic management  LNP 
4. Hypoglycemia secondary to glycemic management  LNP 
5. Hypoglycemia secondary to glycemic management  LNP 
6. Hypoglycemia secondary to glycemic management  LP 
7. Hypoglycemia secondary to glycemic management  LP 
8. Hypoglycemia secondary to glycemic management  LP 
9. Hypoglycemia secondary to glycemic management  LP 
10. Hypoglycemia secondary to glycemic management  LP 
11. Volatile blood glucose secondary to insulin management   LNP 
Thrush and other opportunistic infection (7) 
1. Fungal infection (cutaneous rash) secondary to antibiotics (unspecified)  CNP 
2. Thrush (Candidiasis) secondary to broad spectrum antibiotics (unspecified)   CNP 
3. Thrush (oropharyngeal Candida) secondary to antibiotics (piperacillin and tazobactam)  CNP 
4. Thrush (unspecified) secondary to antibiotics (unspecified)  LNP 
5. Thrush (unspecified) secondary to antibiotics and steroids (unspecified)  CNP 
6. Thrush (unspecified) secondary to antibiotics and steroids (unspecified)  CNP 
7. Thrush (unspecified) secondary to steroids (unspecified)  CNP 
 
continued on next page 
 
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A P P E N D I X   ~   H  
 
 
Table H-2:  Temporary Harm Events, E Level on the NCC MERP Index, Identified 
Among Medicare Beneficiaries by Clinical Category (n=174) (Continued)  
Temporary Harm Event  Preventability 
Events Related to Medication (continued) 
Allergic reaction or side effect related to skin (6) 
1. Generalized pruritic (itching) rash secondary to narcotic analgesic (morphine)  CNP 
2. Hives and facial swelling due to contrast used during cardiac catheterization  LNP 
3. Hives and significant itching secondary to narcotic analgesic (hydromorphone)   CNP 
4. Hives secondary to allergic reaction to antibiotics (moxifloxacin)   CNP 
5. Itching and erythema (redness) secondary to narcotic analgesic (hydromorphone)  CNP 
6. Itching secondary to antibiotics (clindamycin and cephalosporin)  CNP 
Gastrointestinal complication (5) 
1. Allergic reaction (nausea and vomiting) to narcotic analgesics (hydromorphone)   CP 
2. Diarrhea secondary to antibiotic (amoxicillin and clavulanate)  UTD 
3. Nausea and vomiting secondary to hypertension therapy (nitroprusside)   LNP 
4. Nausea and vomiting secondary to narcotic analgesic (morphine)   LNP 
5. Severe diarrhea secondary to laxatives  LP 
Hypotension (5) 
1. Cascade event in which diuretic (furosemide) led to sinus tachycardia, renal 
LP 
insufficiency, and hypotension  
2. Hypotension and dizziness secondary to antihypertensive medication (unspecified)  LP 
3. Hypotension following administration of blood pressure medication (metoprolol)   CP 
4. Hypotension secondary to multiple antihypertensives (unspecified)    LP 
5. Low blood pressure secondary to aggressive diuresis (enalapril and furosemide)  LNP 
Dysrhythmia  (3) 
1. Dysrhythmia secondary to beta-blocker (labetalol)   LNP 
2. Dysrhythmia secondary to cardiac medication (digoxin)   LP 
3. Palpitations and nausea secondary to bronchodilators (albuterol)   CNP 
Excessive bleeding (3) 
1. Epistaxis (nasal bleed) secondary to anticoagulant (enoxaparin)   CNP 
2. Gross hematuria secondary to anticoagulant (heparin)   CNP 
3. Hematuria secondary to anticoagulant (enoxaparin)  LNP 
Severe headache or dizziness (3) 
1. Extended period of dizziness secondary to opioid withdrawal medication 
LP 
(buprenorphine)  
2. Headache secondary to cardiac medication (nitroglycerine)   LP 
3. Nausea and headache secondary to cardiac medication (nitroglycerine)   CNP 
Acute renal failure or insufficiency (2) 
1. Acute renal failure secondary to radiopaque contrast   LNP 
2. Acute renal insufficiency secondary to multiple nephrotoxic agents, including kanamycin 
CP 
and ketorolac 
Allergic reaction to blood or related products (2) 
1. Allergic reaction to blood transfusion  CNP 
2. Hives during infusion of fresh frozen plasma   CNP 
Respiratory complication (2) 
1. Hypoxia secondary to narcotic analgesic (meperidine)  LP 
2. Respiratory acidosis secondary to narcotic analgesic (hydrocodone with 
CP 
acetaminophen) and sedative (alprazolam)  
Other events related to medication (2) 
1. Fever secondary to antiulcer medication used to treat uterine atony (misoprostol)   CNP 
2. Urinary retention secondary to narcotic analgesic (opioid)  LNP 
 
continued on next page 
 
 
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A P P E N D I X   ~   H  
 
Table H-2:  Temporary Harm Events, E Level on the NCC MERP Index, Identified 
Among Medicare Beneficiaries by Clinical Category (n=174 ) (Continued) ( 
Temporary Harm Event  Preventability 
Events Related to Patient Care (63) 
Stage I, Stage II, or unstaged pressure ulcer (20) 
1. Bilateral stage I pressure ulcer (buttocks)  LP 
2. Deep tissue injury (buttock)  LNP 
3. Progression from stage I pressure ulcer to stage II pressure ulcer (coccyx)  CNP 
4. Progression from stage I pressure ulcer to stage II pressure ulcer (coccyx)  LNP 
5. Progression from stage I pressure ulcer to stage II pressure ulcer (coccyx)  LNP 
6. Stage I pressure ulcer (coccyx)  LNP 
7. Stage I pressure ulcer (coccyx)  LNP 
8. Stage I pressure ulcer (heel)  LP 
9. Stage I pressure ulcer (sacrum)  LP 
10. Stage I pressure ulcer (sacrum and buttocks)  LP 
11. Stage I pressure ulcer (unspecified location)  LP 
12. Stage I pressure ulcer secondary to restraints (sacrum and buttock)  LP 
13. Stage II pressure ulcer (buttock)  LP 
14. Stage II pressure ulcer (buttock)  LP 
15. Stage II pressure ulcer (buttock)  UTD 
16. Stage II pressure ulcer (heel and ankle)  LP 
17. Stage II pressure ulcer (sacrum)  CNP 
18. Stage II pressure ulcer (sacrum) and stage I pressure ulcer (heel)  LNP 
19. Stage II pressure ulcer (unspecified location)  LP 
20. Unstaged pressure ulcer (sacrum)  LNP 
IV volume overload (15) 
1. Anasarca secondary to IV fluid resuscitation   LNP 
2. Bilateral pulmonary effusion and pulmonary edema secondary to IV volume overload   LP 
3. Cascade event in which excessive IV fluids administered after a procedure led to 
LP 
volume overload and hyponatremia  
4. Cascade event in which IV volume overload during a procedure led to acute respiratory 
LP 
distress  
5. Cascade event in which the delay of a procedure led to the transfusion of additional 
UTD 
blood products and resulted in dyspnea  
6. Dyspnea and pulmonary congestion secondary to IV volume overload   LNP 
7. Dyspnea and pulmonary edema secondary to IV volume overload of contrast agent   LP 
8. Dyspnea and pulmonary edema secondary to IV volume overload   LP 
9. Dyspnea secondary to fluid overload of contrast agent used during arteriogram   LNP 
10. Dyspnea secondary to IV volume overload of fluids to correct bowel obstruction   LP 
11. Postoperative congestive heart failure secondary to IV volume overload   LNP 
12. Pulmonary edema secondary to IV volume overload   LP 
13. Pulmonary edema secondary to postoperative IV volume overload   LNP 
14. Vascular congestion secondary to fluid resuscitation   LNP 
15. Vascular congestion secondary to IV volume overload of fresh frozen plasma   LP 
Skin tear, laceration, abrasion, or other breakdown (9) 
1. Blisters from telemetry leads (chest)   CP 
2. Laceration during transfer to CT table (ankle)   CP 
3. Skin abrasion from tape removal (IV site)   CNP 
4. Skin breakdown with inflammation and drainage (upper arm)  LNP 
5. Skin breakdown with tear (sacrum)   LP 
6. Skin tear (elbow)   LNP 
7. Skin tear (wrist)   LNP 
8. Skin tear from prosthesis (heel)   LNP 
9. Skin tears from patient turning (elbow and hand)   LNP 
 
continued on next page 
 
 
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Table H-2:  Temporary Harm Events, E Level on the NCC MERP Index, Identified 
Among Medicare Beneficiaries by Clinical Category (n=174) (Continued)  
Temporary Harm Event  Preventability 
Events Related to Patient Care (continued) 
IV infiltrate with symptoms (6) 
1. Cellulitis secondary to IV infiltrate  LNP 
2. IV infiltrate with pain and inflammation  LNP 
3. IV infiltrate with pain and inflammation  LNP 
4. IV infiltrate with pain, inflammation, and edema  LNP 
5. Superficial phlebitis secondary to IV infiltrate  LP 
6. Thrombophlebitis secondary to IV infiltrate  UTD 
Patient fall with injury (5)   
1. Arm and shoulder injury resulting from patient fall  LP 
2. Chest injury resulting from patient fall  LNP 
3. Shoulder contusion and delay in surgery resulting from patient fall  LNP 
4. Skin tear/abrasion on knees resulting from patient fall  CP 
5. Status epilepticus resulting from patient fall with head trauma   LP 
Aspiration (3) 
1. Aspiration associated with endotracheal tube leak  LNP 
2. Aspiration associated with procedure-related infiltrate   LP 
3. Aspiration pneumonitis associated with patients secretions  CNP 
Failure to treat constipation or obstipation (3) 
1. Exacerbation of constipation (impaction) secondary to narcotic analgesic 
(hydromorphone) due to failure to provide sufficient treatment  LP 
2. Exacerbation of constipation secondary to increase in narcotic analgesics (unspecified) 
LP 
due to failure to provide sufficient treatment 
3. Extended period of constipation due to failure to provide sufficient treatment   LP 
Tachycardia or dysrhythmia (2) 
1. Nonsustained ventricular tachycardic dysrhythmia  LP 
2. Paroxysmal supraventricular tachycardia  UTD 
Events Related to Surgery or Other Procedures (32) 
Urinary retention (8) 
1. Postoperative urinary retention associated with indwelling catheter  CNP 
2. Postoperative urinary retention associated with indwelling catheter   LP 
3. Postoperative urinary retention associated with indwelling catheter   LP 
4. Postoperative urinary retention associated with straight catheter  LNP 
5. Postoperative urinary retention associated with straight catheter  CNP 
6. Postoperative urinary retention following back surgery  LNP 
7. Postoperative urinary retention following hip surgery  LNP 
8. Postoperative urinary retention following hip surgery  LNP 
Excessive bleeding (6) 
1. Anemia following hip surgery  LNP 
2. Bleeding from femoral catheter site  LNP 
3. Bleeding from femoral catheter site following dialysis   LNP 
4. Hematoma and bleeding from IV site   LP 
5. Hematoma and drop in hemoglobin following hip surgery   LNP 
6. Hematoma secondary to IV extravasation  LNP 
Cardiac complication (4) 
1. Atrial fibrillation and palpitations following thoracotomy   CNP 
2. Atrial fibrillation following cystoscopy   LNP 
3. Minor myocardial infarction following neck surgery   CNP 
4. Paroxysmal supraventricular tachycardia following surgery   LNP 
 
continued on next page 
 
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Table H-2:  Temporary Harm Events, E Level on the NCC MERP Index, Identified 
Among Medicare Beneficiaries by Clinical Category (n=174) (Continued) 
Temporary Harm Event  Preventability 
Events Related to Surgery or Other Procedures (continued) 
Surgical tear or laceration (3) 
1. Dural tear during discectomy and spinal decompression   LNP 
2. Dural tear during laminectomy  LNP 
3. Unintentional enterotomy during surgery to relieve bowel obstruction  LNP 
Urinary catheter-related trauma (3) 
1. Hematuria associated with indwelling urinary catheter  LNP 
2. Postoperative hematuria associated with indwelling urinary catheter  CNP 
3. Postoperative hematuria associated with indwelling urinary catheter  LNP 
Prolonged nausea and vomiting (2) 
1. Prolonged nausea and vomiting following spinal surgery   LNP 
2. Prolonged nausea and vomiting secondary to anesthetic given for dilation and curettage   CNP 
 Postoperative or postprocedural hypotension (2) 
1. Hypotension following cardiac procedure  LP 
2. Hypotension following nephrectomy  LNP 
Respiratory complication (2) 
1. Dyspnea following nephrectomy    UTD 
2. Hypoxemia following shoulder arthroplasty   UTD 
 Other events related to surgery or other procedures (2) 
1. Gout following pacemaker placement procedure   CNP 
2. Ileus following hip arthroplasty   LNP 
Events Related to Infection (6) 
Surgical site infection (2) 
1. Surgical site infection following colostomy procedure   LNP 
2. Surgical site infection following hip surgery   LP 
Bacterial infection (1) 
1. Bacterial parotiditis (glandular) infection   LNP 
Respiratory infection (1) 
1. Postoperative pneumonia  LNP 
Urinary tract infection (1) 
    1.  Urinary tract infection related to urostomy  LNP 
Vascular catheter-associated infection (1) 
1. Infectious phlebitis at catheter insertion site  LP 
Source:  OIG analysis of hospital stays for 780 Medicare beneficiaries in October 2008. 
 
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A  P  PEN  0 
Agency Comments:  Agency for Healthcare Research and Quality 
DEPARTMENT OF HEALTH AND HUMAN SERVICES 	 Agency for Healthcar. 
Research and Quality 
540 Gaither Road 
SEP  2 2 2010  Rockville, MD 20850
www.ahrq.gov 
TO: 	 Daniel R, Levinson 

Inspector General 

FROM: 	 Carolyn M. Clancy, MD 

Director 

SUBJECT: 	 AHRQ Response to OIG draft report, Adverse Events in Hospitals: National Incidence 
Among Medicare Beneficiaries, OEI-06-09-00090. 
Thank you for the opportunity to review your draft report, Adverse Events in Hospitals: National 
Incidence Among Medicare Beneficiaries, OEI-06-09-00090 . .The findings in the report are consistent 
with previous studies but are nonetheless disturbing. They confirm that adverse events continue to 
affect hospital inpatients at an alarming rate, and that the types of events that occur vary widely, The 
report reaffirms AHRQ's need to continue work on improving patient safety by broadening investigation 
to include areas that are not always seen on lists of adverse events that should never occur or should 
always be reported. 
Responses are provided below to the report's two general recommendations that pertain to AHRQ and 
were provided in the July 20, 2010, draft version of the report that the Agency reviewed. AHRQ concurs 
with both OIG recommendations.  . 
Recommendation: AHRQ and CMS should broaden patient safety efforts to include all types of adverse 
events. 
AHRQ Response: CONCUR 
AHRQ agrees that efforts to improve patient safety should be broad. While we have sponsored efforts 
to address specific types of adverse events, such as central-line-associated bloodstream infections and 
venous thromboembolisms, we have also supported efforts to address underlying causes that 
contribute to a wide variety of adverse events. For example, we have focused on improving the safety 
culture in healthcare by providing a widely-adopted patient safety culture survey that is used by 
hospitals and healthcare systems, and by providing team training to healthcare systems via the 
TeamSTEPPS program that we developed in concert with the Department of Defense. We have also 
provided broad in-person training on the topic of patient safety improvement to public sector and 
private sector representatives from every state via the Patient Safety Improvement Corps, which we 
implemented in concert with the Department of Veterans Affairs' National Center for Patient Safety.  As 
we continue to lead and support Federal efforts in patient safety improvement, we intend to broaden 
efforts to improve patient safety overall (as with TeamSTEPPS), and to address specific problems, such 
as a targeted program to foster the widespread implementation of the CDC's guideline to prevent 
catheter-associated urinary tract infections. 
1 
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  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   63   APPEND  X 
Agency Comments: Centers for Medicare & Medicaid Services 
( -I.. 
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DEPARTMENT OF HEALTH & HUMAN SERVICES  Center. for Medicare & Medicaid Servicas 
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(; 
 Administrator 
Washington, DC 20201 
SEP  0 92010
DATE: 
TO:  Daniel R. Levinson 	
,..." 
Inspector General  '= 
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FROM:  :"C1"'':1l"1 ''  .. -u  )' 1
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Thank. you for the opportunity to review and comment on the subject OIG Draft Report, 
"Adverse Events in Hospitals: National Incidence Among Medicare Beneficiaries, OEI-06-09
00090." We appreciate the OIG's work on this important and timely topic. When one in eight 
hospitalized Medicare beneficiaries experience an adverse event, most ofwhich result in a 
prolonged hospital stay, permanent harm, life-saving interventions, or death, solutions need to be 
addressed as quickly and efficiently as possible. The Centers for Medicare & Medicaid Services 
(CMS) has taken significant steps to address these issues, but more work needs to be done. 
The report's findings provide new information to the Department of Health and Human Services 
(HHS) broadly, and the Centers for Medicare & Medicaid Services (CMS) specifically, upon 
which to act to expand efforts to work with hospitals and clinicians to prevent adverse events. 
CMS seeks to promote a culture of safety across the country in all health care settings. While the 
report characterizes CMS as an oversight entity and the nation's largest health payer, CMS is 
also actively transitioning from serving solely as a regulator and passive payer of health care 
services to an agency that fully supports public health goals as an active payer of high quality 
and efficient care. 
CMS is also an engine for innovation across health care.  Several new legislative and regulatory 
enarts, including the new Center for Medicare & Medicaid Il1novation, provide us with new and 
innovative tools to address the concerns raised in this report. In addition, we plan to continue 
several efforts already in progress to reduce adverse events. While this response focuses on 
adverse events in hospitalized patients, our efforts are also directed at addressing issues in 
dialysis centers and ambulatory and long term care settings, recognizing that in our dynamic and 
complex healthcare system a patient should expect and receive safe care, wherever that care may 
be provided. 
While we have a number of efforts already underway (as discussed throughout this response), we 
are launching a number ofnew efforts to infuse a cross-cutting theme of safety throughout the 
agency to promote a coordinated effort among existing and emerging programs. These are all 
designed to create incentives for and support to hospitals to identify adverse events, practices to 
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 A C K N O W L E D G M E N T S  
 
This report was prepared under the direction of Kevin K. Golladay, 
Regional Inspector General for Evaluation and Inspections in the Dallas 
regional office, and A. Blaine Collins, Deputy Regional Inspector 
General.   
Amy Ashcraft and Ruth Ann Dorrill served as the team leaders for this 
study.  Other principal Office of Evaluation and Inspections staff from 
the Dallas regional office who contributed to the report include Deborah 
Cosimo, Nathan Dong, Ben Gaddis, Jennifer Gist, Anthony       
Guerrero-Soto, Deborah McGurk, and Jeremy Moore; central office staff 
who contributed include Rob Gibbons, Sandy Khoury, Sue Nonemaker, 
Arianne Spaccarelli, and Rita Wurm. 
  OEI-06-09-00090  ADVERSE EVENTS IN HOSPITALS:  NATIONAL INCIDENCE AMONG MEDICARE BENEFICIARIES   74    
Office of Inspector General 
http://oig.hhs.gov 
 
The mission of the Office of Inspector General (OIG), as mandated by Public Law 95-452, as 
amended, is to protect the integrity of the Department of Health and Human Services 
(HHS) programs, as well as the health and welfare of beneficiaries served by those 
programs.  This statutory mission is carried out through a nationwide network of audits, 
investigations, and inspections conducted by the following operating components: 
Office of Audit Services 
The Office of Audit Services (OAS) provides auditing services for HHS, either by conducting 
audits with its own audit resources or by overseeing audit work done by others.  Audits 
examine the performance of HHS programs and/or its grantees and contractors in carrying 
out their respective responsibilities and are intended to provide independent assessments of 
HHS programs and operations.  These assessments help reduce waste, abuse, and 
mismanagement and promote economy and efficiency throughout HHS. 
Office of Evaluation and Inspections 
The Office of Evaluation and Inspections (OEI) conducts national evaluations to provide 
HHS, Congress, and the public with timely, useful, and reliable information on significant 
issues.  These evaluations focus on preventing fraud, waste, or abuse and promoting 
economy, efficiency, and effectiveness of departmental programs.  To promote impact, OEI 
reports also present practical recommendations for improving program operations.  
Office of Investigations 
The Office of Investigations (OI) conducts criminal, civil, and administrative investigations 
of fraud and misconduct related to HHS programs, operations, and beneficiaries.  With 
investigators working in all 50 States and the District of Columbia, OI utilizes its resources 
by actively coordinating with the Department of Justice and other Federal, State, and local 
law enforcement authorities.  The investigative efforts of OI often lead to criminal 
convictions, administrative sanctions, and/or civil monetary penalties. 
Office of Counsel to the Inspector General 
The Office of Counsel to the Inspector General (OCIG) provides general legal services to 
OIG, rendering advice and opinions on HHS programs and operations and providing all 
legal support for OIGs internal operations.  OCIG represents OIG in all civil and 
administrative fraud and abuse cases involving HHS programs, including False Claims Act, 
program exclusion, and civil monetary penalty cases.  In connection with these cases, OCIG 
also negotiates and monitors corporate integrity agreements.  OCIG renders advisory 
opinions, issues compliance program guidance, publishes fraud alerts, and provides other 
guidance to the health care industry concerning the anti-kickback statute and other OIG 
enforcement authorities.