Incidence and associations of acute kidney injury after major abdominal surgery

PurposeAcute kidney injury (AKI) is a recognised risk factor for adverse outcomes in critical illness and hospitalised patients in general. To understand the incidence and associations of AKI as a peri-operative complication of major abdominal surgery, we conducted a systematic literature review and meta-analysis.MethodsUsing a systematic strategy, we searched the electronic reference databases for articles describing post-operative renal outcomes using consensus criteria for AKI diagnosis (RIFLE, AKIN or KDIGO) in the setting of major abdominal surgery. Pooled incidence of AKI and, where reported, pooled relative risk of death after post-operative AKI were estimated using random effects models.ResultsFrom 4287 screened titles, 19 articles met our inclusion criteria describing AKI outcomes in 82,514 patients undergoing abdominal surgery. Pooled incidence of AKI was 13.4 % (95 % CI 10.9–16.4 %). In eight studies that reported the short-term mortality, relative risk of death in the presence of post-operative AKI was 12.6 fold (95 % CI, 6.8–23.4). Where reported, length of stay was greater and non-renal post-operative complications were also more frequent in patients experiencing AKI.ConclusionsUsing modern consensus definitions, AKI is a common complication of major abdominal surgery that is associated with adverse patient outcomes including death. While a causative role for AKI cannot be concluded from this analysis, as an important signal of peri-operative harm, AKI should be regarded as an important surgical outcome measure and potential target for clinical interventions.

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title: Acute kidney injury, mortality, length of stay, and costs in hospitalized patients.
abstract: The marginal effects of acute kidney injury on in-hospital mortality, length of stay (LOS), and costs have not been well described. A consecutive sample of 19,982 adults who were admitted to an urban academic medical center, including 9210 who had two or more serum creatinine (SCr) determinations, was evaluated. The presence and degree of acute kidney injury were assessed using absolute and relative increases from baseline to peak SCr concentration during hospitalization. Large increases in SCr concentration were relatively rare (e.g., >or=2.0 mg/dl in 105 [1%] patients), whereas more modest increases in SCr were common (e.g., >or=0.5 mg/dl in 1237 [13%] patients). Modest changes in SCr were significantly associated with mortality, LOS, and costs, even after adjustment for age, gender, admission International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis, severity of illness (diagnosis-related group weight), and chronic kidney disease. For example, an increase in SCr >or=0.5 mg/dl was associated with a 6.5-fold (95% confidence interval 5.0 to 8.5) increase in the odds of death, a 3.5-d increase in LOS, and nearly 7500 dollars in excess hospital costs. Acute kidney injury is associated with significantly increased mortality, LOS, and costs across a broad spectrum of conditions. Moreover, outcomes are related directly to the severity of acute kidney injury, whether characterized by nominal or percentage changes in serum creatinine.

title: Acute renal failure in critically ill patients: a multinational, multicenter study.
abstract: Although acute renal failure (ARF) is believed to be common in the setting of critical illness and is associated with a high risk of death, little is known about its epidemiology and outcome or how these vary in different regions of the world.



To determine the period prevalence of ARF in intensive care unit (ICU) patients in multiple countries; to characterize differences in etiology, illness severity, and clinical practice; and to determine the impact of these differences on patient outcomes.



Prospective observational study of ICU patients who either were treated with renal replacement therapy (RRT) or fulfilled at least 1 of the predefined criteria for ARF from September 2000 to December 2001 at 54 hospitals in 23 countries.



Occurrence of ARF, factors contributing to etiology, illness severity, treatment, need for renal support after hospital discharge, and hospital mortality.



Of 29 269 critically ill patients admitted during the study period, 1738 (5.7%; 95% confidence interval [CI], 5.5%-6.0%) had ARF during their ICU stay, including 1260 who were treated with RRT. The most common contributing factor to ARF was septic shock (47.5%; 95% CI, 45.2%-49.5%). Approximately 30% of patients had preadmission renal dysfunction. Overall hospital mortality was 60.3% (95% CI, 58.0%-62.6%). Dialysis dependence at hospital discharge was 13.8% (95% CI, 11.2%-16.3%) for survivors. Independent risk factors for hospital mortality included use of vasopressors (odds ratio [OR], 1.95; 95% CI, 1.50-2.55; P<.001), mechanical ventilation (OR, 2.11; 95% CI, 1.58-2.82; P<.001), septic shock (OR, 1.36; 95% CI, 1.03-1.79; P = .03), cardiogenic shock (OR, 1.41; 95% CI, 1.05-1.90; P = .02), and hepatorenal syndrome (OR, 1.87; 95% CI, 1.07-3.28; P = .03).



In this multinational study, the period prevalence of ARF requiring RRT in the ICU was between 5% and 6% and was associated with a high hospital mortality rate.

title: Acute kidney injury criteria predict outcomes of critically ill patients*
abstract: The Acute Kidney Injury Network's proposed definition for acute kidney injury (increment of serum creatinine ≥0.3 mg/dL or 50% from baseline within 48 hrs or urine output <0.5 mL/kg/hr for >6 hrs despite fluid resuscitation when applicable) predicts meaningful clinical outcomes. Retrospective cohort study. A 350-bed community teaching hospital. The study population consisted of 471 patients with no recent history of renal replacement therapy who were admitted to the medical intensive care unit during 1 yr. Medical records of all patients were reviewed using a data abstraction tool. Demographic information, diagnoses, risk factors for acute kidney disease, physiologic and laboratory data, and outcomes were recorded. Of 496 patients, 471 were not receiving renal replacement therapy in the weeks before medical intensive care unit admission; 213 had changes ≥.3 mg/dL in serum creatinine within 48 hrs and/or urine output of ≤.5 mL/kg/hr for >6 hrs. Detailed fluid challenge information was available for only 123 patients, who met acute kidney injury criteria, and three patients reversed after administration of ≥500 mL of intravenous fluid and/or blood products. All patients whose creatinine increased ≥50% also had increments ≥0.3 mg/dL. The 120 patients with acute kidney injury were older (mean ± se: 69.3 ± 1.7 vs. 62.9 ± 1.3, p < .01), were more ill (Acute Physiology and Chronic Health Evaluation II score 18.7 ± .6 vs. 13.3 ± .4, p < .01), and had multiple comorbidities (two or more organs, 65% vs. 51.3%, p < .01) compared with those without acute kidney injury. The mortality rate of patients who met criteria for acute kidney injury was significantly higher than that of patients who did not have acute kidney injury (45.8 vs. 16.4%, p < .01). In multivariate logistic regression analyses, acute kidney injury was an independent predictor of mortality (adjusted odds ratio 3.7, 95% confidence interval 2.2–6.1). Acute kidney injury was a better predictor of in-hospital mortality than was Acute Physiology and Chronic Health Evaluation II score, advanced age, or presence of nonrenal organ failures. Median hospital stay was twice as long in patients with acute kidney injury (14 vs. 7 days, p < .01), and only patients with acute kidney injury required hemodialysis during hospitalization. The oliguria criterion of acute kidney injury did not affect the odds of in-hospital mortality. The Acute Kidney Injury Network definition of acute kidney injury predicts hospital mortality, need for renal replacement therapy, and prolonged hospital stay in critically ill patients. An increment of serum creatinine ≥0.3 mg/dL in 48 hrs alone predicts clinical outcomes as well as the full Acute Kidney Injury Network definition.

title: Risk factors for morbidity and mortality after colectomy for colon cancer
abstract: Comorbid conditions affect the risk of adverse outcomes after surgery, but the magnitude of risk has not previously been quantified using multivariate statistical methods and prospectively collected data. Identifying factors that predict results of surgical procedures would be valuable in assessing the quality of surgical care. This study was performed to define risk factors that predict adverse events after colectomy for cancer in Department of Veterans Affairs Medical Centers.  The National Veterans Affairs Surgical Quality Improvement Program contains prospectively collected and extensively validated data on more than 415,000 surgical operations. All patients undergoing colectomy for colon cancer from 1991 to 1995 who were registered in the National Veterans Affairs Surgical Quality Improvement Program database were selected for study. Independent variables examined included 68 preoperative and 12 intraoperative clinical risk factors; dependent variables were 21 specific adverse outcomes. Stepwise logistic regression analysis was used to construct models predicting the 30-day mortality rate and 30-day morbidity rates for each of the ten most frequent complications.  A total of 5,853 patients were identified; 4,711 (80 percent) underwent resection and primary anastomosis. One or more complications were observed in 1,639 of 5,853 (28 percent) patients. Prolonged ileus (439/5,853; 7.5 percent), pneumonia (364/5,853; 6.2 percent), failure to wean from the ventilator (334/5,853; 5.7 percent), and urinary tract infection (292/5,853; 5 percent) were the most frequent complications. The 30-day mortality rate was 5.7 percent (335/5,853). For most complications, 30-day in-hospital mortality rates were significantly higher for patients with a complication than for those without. Thirty-day mortality rates exceeded 50 percent if postoperative coma, cardiac arrest, a pre-existing vascular graft prosthesis that failed after colectomy, renal failure, pulmonary embolism, or progressive renal insufficiency occurred. Preoperative factors that predicted a high risk of 30-day mortality included ascites, serum sodium >145 mg/dl, “do not resuscitate” status before surgery, American Society of Anesthesiologists classes III and IV OR V, and low serum albumin.  Mortality rates after colectomy in Veterans Affairs hospitals are comparable with those reported in other large studies. Ascites, hypernatremia, do not resuscitate status before surgery, and American Society of Anesthesiologists classes III and IV OR V were strongly predictive of perioperative death. Clinical trials to decrease the complication rate after colectomy for colon cancer should focus on these risk factors.

title: Long-Term Risk of Mortality and Acute Kidney Injury During Hospitalization After Major Surgery
abstract: To determine the relationship between long-term mortality and acute kidney injury (AKI) during hospitalization after major surgery. AKI is associated with a risk of short-term mortality that is proportional to its severity; however the long-term survival of patients with AKI is poorly studied. This is a retrospective cohort study of 10,518 patients with no history of chronic kidney disease who were discharged after a major surgery between 1992 and 2002. AKI was defined by the RIFLE (Risk, Injury, Failure, Loss, and End-stage Kidney) classification, which requires at least a 50% increase in serum creatinine (sCr) and stratifies patients into 3 severity stages: risk, injury, and failure. Patient survival was determined through the National Social Security Death Index. Long-term survival was analyzed using a risk-adjusted Cox proportional hazards regression model. In the risk-adjusted model, survival was worse among patients with AKI and was proportional to its severity with an adjusted hazard ratio of 1.18 (95% confidence interval [CI], 1.08–1.29) for the RIFLE-Risk class and 1.57 (95% CI, 1.40–1.75) for the RIFLE-Failure class, compared with patients without AKI (P < 0.001). Patients with complete renal recovery after AKI still had an increased adjusted hazard ratio for death of 1.20 (95% CI, 1.10–1.31) compared with patients without AKI (P < 0.001). In a large single-center cohort of patients discharged after major surgery, AKI with even small changes in sCr level during hospitalization was associated with an independent long-term risk of death.

title: The effect of acute renal failure on mortality. A cohort analysis.
abstract: To determine if the high mortality in acute renal failure is explained by underlying illnesses (comorbidity).



Cohort analytic study.



An 826-bed general hospital providing primary, secondary, and tertiary care.



From 16,248 inpatients undergoing radiocontrast procedures between 1987 and 1989, we identified 183 index subjects who developed contrast media-associated renal failure (defined as an increase in serum creatinine level of at least 25%, to at least 177 micromol/L [2 mg/dL], within 2 days of receiving contrast material) and 174 paired subjects, matched for age and baseline serum creatinine level, who underwent similar contrast procedures without developing renal failure.



Death during hospitalization.



The mortality rate in subjects without renal failure was 7%, compared with 34% in the corresponding index subjects with renal failure (odds ratio, 6.5; P<.001). After adjusting for differences in comorbidity, renal failure was associated with an odds ratio of dying of 5.5. Subjects who died after developing renal failure had complicated clinical courses characterized by sepsis, bleeding, delirium, and respiratory failure; most of these complications developed after the onset of renal failure. Deaths from renal causes were rare.



The high mortality rate in acute renal failure is not explained by the underlying conditions alone. Renal failure appears to increase the risk of developing severe nonrenal complications that lead to death and should not be regarded as a treatable complication of serious illness.

title: An assessment of the RIFLE criteria for acute renal failure in hospitalized patients*
abstract: The Acute Dialysis Quality Initiative (ADQI) Group published a consensus definition (the RIFLE criteria) for acute renal failure. We sought to assess the ability of the RIFLE criteria to predict mortality in hospital patients. Retrospective single-center study. University-affiliated hospital. All patients admitted to the study hospital between January 2000 and December 2002. Patients were excluded if they were younger than 15 yrs old, were on chronic dialysis, or had kidney transplant or if their length of hospital stay was <24 hrs. None. We included 20,126 patients. Mean age was 64 yrs, 14.7% of patients required intensive care unit admission, and hospital mortality was 8.0%. According to the RIFLE criteria, 9.1% of all patients were in the Risk category for acute renal failure, 5.2% were in the Injury category, and 3.7% were in the Failure category. There was an almost linear increase in hospital mortality from Normal to Failure (Normal, 4.4%; Risk, 15.1%; Injury, 29.2%; and Failure, 41.1%). Multivariate logistic regression analysis showed that all RIFLE criteria were significantly predictive factors for hospital mortality, with an almost linear increase in odds ratios from Risk to Failure (odds ratios, Risk 2.5, Injury 5.4, Failure 10.1). The RIFLE criteria for acute renal failure classified close to 20% of our study patients as having some degrees of acute impairment in renal function and were useful in predicting their hospital mortality.

title: Long-term survival after cardiac surgery is predicted by estimated glomerular filtration rate.
abstract: Estimated glomerular filtration rate (eGFR) before coronary artery bypass graft (CABG) surgery is a key risk factor of in-hospital mortality. However, in patients with normal renal function before CABG, acute kidney injury develops after the procedure, making postoperative renal function assessment necessary for evaluation. Postoperative eGFR and its association with long-term survival have not been well studied.



We studied 13,593 consecutive CABG patients in northern New England from 2001 to 2006. Patients with preoperative dialysis were excluded. Data were linked to the Social Security Association Death Master File to assess long-term survival. Kaplan-Meier and log-rank techniques were used. Patients were stratified by established categories of postoperative eGFR (90 or greater, 60 to 89, 30 to 59, 15 to 29, and less than 15 mL x min(-1) x 1.73 m(-2)).



Median follow-up was 2.8 years (mean, 2.7; range, 0 to 5.5). Patients with moderate to severe acute kidney injury (less than 60) after CABG had significantly worse survival than patients with little or no acute kidney injury (90 or greater).



Patients having moderate to severe acute kidney injury after CABG surgery had worse 5-year survival compared with patients who had normal or near-normal renal function.

title: Cardiopulmonary bypass management and acute renal failure: risk factors and prognosis
abstract: The aim of the study was to investigate if acute renal failure (ARF) following cardiac surgery is influenced by CPB perfusion pressure and to determine risk factors of ARF. Our research consisted of two studies. In the first study, 179 adult patients with normal preoperative renal function who had been subjected to cardiac surgery on CPB were randomized into three groups. The mean perfusion pressure (PP) during CPB in Group 65 (68 patients) was 60–69.9 mmHg, in Group 55 (59 patients) – lower than 60 mmHg and in Group 75 (52 patients) – 70 mmHg and higher. We have analyzed postoperative variables: central venous pressure, the need for diuretics, urine output, fluid balance, acidosis, potassium level in blood serum, the need for hemotransfusions, nephrological, cardiovascular and respiratory complications, duration of artificial lung ventilation, duration of stay in ICU and in hospital, and mortality. In the second study, to identify the risk factors for the development of ARF following CPB, we retrospectively analysed data of all 179 patients, divided into two groups: patients who developed ARF after surgery (group with ARF, n = 19) and patients without ARF (group without ARF, n = 160). We found that urine output during surgery was statistically significantly lower in Group 55 than in Groups 65 and 75. The incidence of ARF in the early postoperative period did not differ among the groups: it developed in 6% of all patients in Group 65, 4% in Group 55 and 6% in Group 75. There were no differences in the rate of other complications (cardiovascular, respiratory, neurological disorders, bleeding, etc) among the groups. There were 19 cases of ARF (10.6%), but none of these patients needed dialysis. We found that age (70.0 ± 7.51 vs. 63.5 ± 10.54 [standard deviation, SD], P = 0.016), valve replacement and/or reconstruction surgery (57.9% vs. 27.2%, P = 0,011), combined valve and CABG surgery (15.8% vs. 1.4%, P = 0.004), duration of CPB (134.74 ± 62.02 vs. 100.59 ± 43.99 min., P = 0.003) and duration of aortic cross-clamp (75.11 ± 35.78 vs. 53.45 ± 24.19 min., P = 0.001) were the most important independent risk factors for ARF. Cardiopulmonary bypass perfusion pressure did not cause postoperative renal failure. The age of patient, valve surgery procedures, duration of cardiopulmonary bypass and duration of aorta cross-clamp are potential causative factors for acute renal failure after cardiac surgery.

title: RIFLE criteria for acute kidney injury in valvular surgery.
abstract: The RIFLE classification, which defines three grades of increasing severity of acute kidney injury--risk (RIFLE R), injury (RIFLE I) and failure (RIFLE F), and two outcome classes (L, loss) and E (end-stage kidney disease)--represents a valuable method for evaluating acute renal failure. Risk factors for acute kidney injury (AKI) according to the RIFLE criteria and for operative mortality were identified in patients undergoing valvular procedures.



A single-center prospective cohort study of 1424 patients who were not receiving renal replacement therapy preoperatively was conducted between January 2004 and December 2007. A total of 100 variables was collected from each patient.



The main features were: mean age 61.9 +/- 12.9 years (range: 15-88 years), 47% females, 6% endocarditis, 11% redo surgery, 8% urgent/emergent surgery, 30% combined procedures, 5% complex, and 16% associated coronary artery bypass grafting (CABG). The overall AKI prevalence was 10%, with RIFLE scores of I or F being detected in 8% and continuous veno-venous hemofiltration being required in 5%. Risk factors for AKI were age (OR 1.03; 95% CI 1.14-4.15), time of extracorporeal circulation (ECC) (OR 1.09; 95% CI 1.005-1.013), redo procedure (OR 2.35; 95% CI 1.42-3.8), chronic kidney disease (OR 3.2; 95% CI 1.6-6.1), and blood transfusion (OR 3.8; 95% CI 2.5-6.5). The transfusion of leukodepleted blood exerted a protective effect on AKI development (OR 0.6; 95% CI 0.4-0.9). The average overall hospital mortality was 4.8%. Risk factors for operative mortality included: ECC time (OR 1; 95% CI 1.002-1.014), age (OR 1.043; 95% CI 1.01-1.07), chronic kidney disease (OR 4.8; 95% CI 2.2-10.6), blood transfusion (OR 6.43; 95% CI 2.8-14.7), surgical priority (OR 6.5; 95% CI 2.8-14.7), RIFLE class I (OR 11.9; 95% CI 5.5-25.7), and RIFLE class F (OR 30; 95% CI 8.1-111.7). Mortality increased with each RIFLE stratification (Normal 1.7%, RIFLE R = 4.1%, RR = 2.5; RIFLE I = 27.6%, RR = 16.2; and RIFLE F = 43.8% RR = 25.8).



AKI is a highly prevalent and prognostically important complication, for which the majority of risk factors that have been identified are not modifiable. The transfusion of leukodepleted blood products was seen to exert a preventive effect.

title: Off-pump coronary artery bypass surgery and acute kidney injury: a meta-analysis of randomized controlled trials.
abstract: Off-pump coronary artery bypass grafting (CABG) has been advocated to cause less inflammation, morbidity, and mortality than the more traditional on-pump technique. This meta-analysis compares these two surgical techniques with respect to causing acute kidney injury (AKI).



This study searched for randomized controlled trials in MEDLINE and abstracts from the proceedings of scientific meetings through February 2010. Included were trials comparing off-pump to on-pump CABG that reported the incidence of AKI, as defined by a mixture of criteria including biochemical parameter/urine output/dialysis requirement. Mortality was evaluated among the studies that reported kidney-related outcomes. For primary and subgroup analyses, fixed-effect meta-analyses of odds ratios (OR) were performed.



In 22 identified trials (4819 patients), the weighted incidence of AKI in the on-pump CABG group was 4.0% (95% confidence interval [CI] 1.8%, 8.5%), dialysis requirement 2.4% (95% CI 1.6%, 3.7%), and mortality 2.6% (95% CI 1.6%, 4.0%). By meta-analysis, off-pump CABG was associated with a 40% lower odds of postoperative AKI (OR 0.60; 95% CI 0.43, 0.84; P = 0.003) and a nonsignificant 33% lower odds for dialysis requirement (OR 0.67; 95% CI 0.40, 1.12; P = 0.12). Within the selected trials, off-pump CABG was not associated with a significant decrease in mortality.



Off-pump CABG may be associated with a lower incidence of postoperative AKI but may not affect dialysis requirement, a serious complication of cardiac surgery. However, the different definitions of AKI used in individual trials and methodological concerns preclude definitive conclusions.

title: Predictive models for acute kidney injury following cardiac surgery.
abstract: Accurate prediction of cardiac surgery-associated acute kidney injury (AKI) would improve clinical decision making and facilitate timely diagnosis and treatment. The aim of the study was to develop predictive models for cardiac surgery-associated AKI using presurgical and combined pre- and intrasurgical variables.



Prospective observational cohort.



25,898 patients who underwent cardiac surgery at Cleveland Clinic in 2000-2008.



Presurgical and combined pre- and intrasurgical variables were used to develop predictive models.



Dialysis therapy and a composite of doubling of serum creatinine level or dialysis therapy within 2 weeks (or discharge if sooner) after cardiac surgery.



Incidences of dialysis therapy and the composite of doubling of serum creatinine level or dialysis therapy were 1.7% and 4.3%, respectively. Kidney function parameters were strong independent predictors in all 4 models. Surgical complexity reflected by type and history of previous cardiac surgery were robust predictors in models based on presurgical variables. However, the inclusion of intrasurgical variables accounted for all explained variance by procedure-related information. Models predictive of dialysis therapy showed good calibration and superb discrimination; a combined (pre- and intrasurgical) model performed better than the presurgical model alone (C statistics, 0.910 and 0.875, respectively). Models predictive of the composite end point also had excellent discrimination with both presurgical and combined (pre- and intrasurgical) variables (C statistics, 0.797 and 0.825, respectively). However, the presurgical model predictive of the composite end point showed suboptimal calibration (P < 0.001).



External validation of these predictive models in other cohorts is required before wide-scale application.



We developed and internally validated 4 new models that accurately predict cardiac surgery-associated AKI. These models are based on readily available clinical information and can be used for patient counseling, clinical management, risk adjustment, and enrichment of clinical trials with high-risk participants.

title: Risk factors for perioperative acute kidney injury after adult cardiac surgery: role of perioperative management.
abstract: The development of acute kidney injury (AKI) after adult cardiac surgery is associated with increased morbidity and mortality. Our aim was to assess the risk factors for postoperative AKI and whether the addition of perioperative management variables can improve AKI prediction.



We studied 3,219 patients operated from January 2006 to December 2009. The AKI was defined as proposed by the Acute Kidney Injury Network. Patient preoperative characteristics, as well as intraoperative, cardiopulmonary bypass (CPB), and postoperative management variables, were evaluated for association with AKI with logistic regression analysis. The model including all variables was assessed first, then separate models including only preoperative variables followed by the sequential addition of intraoperative, CPB, and postoperative management variables were tested; receiver operating characteristic analysis was used to evaluate and compare models' discriminatory power.



The AKI occurred in 288 of 3,219 patients (8.9%). Logistic regression analysis identified 15 predictors of AKI; 4 were preoperative (age, diabetes, smoking, and serum creatinine), 4 intraoperative (inotropes, erythrocytes transfusion, cross-clamp time, and need of a new pump run), 2 CPB-related (urine output and furosemide administration during CPB), and 5 postoperative (erythrocytes transfusion, administration of vasoconstrictors, inotropes, diuretics, and antiarrhythmics). Model-discrimination performance improved from an area under the curve of 0.830 (95% confidence interval 0.807 to 0.854) for the model including only preoperative variables to an area under the curve of 0.904 (95% confidence interval 0.886 to 0.921) for the model including all variables (p<0.001).



Several factors influence AKI development after cardiac surgery and perioperative patient management significantly affects AKI occurrence. Predictive models can be sensibly improved by the addition of these variables.

title: Preoperative statin use and postoperative acute kidney injury.
abstract: Acute kidney injury is a frequent postoperative complication that confers increased mortality, morbidity, and costs. The purpose of this study was to evaluate whether preoperative statin use is associated with a decreased risk of postoperative acute kidney injury.



We assembled a retrospective cohort of 98,939 patients who underwent a major open abdominal, cardiac, thoracic, or vascular procedure between 2000 and 2010. Statin users were pair-matched to nonusers on the basis of surgery type, baseline kidney function, days from admission until surgery, and propensity score based on demographics, comorbid conditions, and concomitant medications. Acute kidney injury was defined based on changes in serum creatinine measurements applying Acute Kidney Injury Network and Risk-Injury-Failure staging systems, and on the need for renal replacement therapy. Associations between statin use and acute kidney injury were estimated by conditional logistic regression.



Across various acute kidney injury definitions, statin use was consistently associated with a decreased risk: adjusted odds ratios (95% confidence intervals) varied from 0.74 (0.58-0.95) to 0.80 (0.71-0.90). Associations were similar among diabetics and nondiabetics, and across strata of baseline kidney function. The protective association of statins was most pronounced among patients undergoing vascular surgery and least among patients undergoing cardiac surgery.



Preoperative statin use is associated with a decreased risk of postoperative acute kidney injury. Future randomized clinical trials are needed to determine causality.

title: Risk factors of postoperative acute kidney injury in patients undergoing esophageal cancer surgery.
abstract: The purpose of this study was to identify perioperative risk factors for postoperative acute kidney injury (AKI) in patients undergoing esophageal cancer surgery.



A retrospective analysis of the prospectively collected medical data.



A tertiary care university hospital.



All consecutive adult patients (n=595) who underwent elective esophageal surgery for cancer between January 2005 and April 2012.



None.



AKI was defined by the AKI Network criteria based on serum creatinine changes within the first 48 hours after esophageal cancer surgery. The relationship between perioperative variables and AKI was evaluated using multivariate logistic regression. Postoperative AKI developed in 210 (35.3%) patients. Risk factors for AKI were body mass index (odds ratio [OR] 1.07; 95% confidence interval [CI] 1.01-1.14), preoperative serum albumin level (OR 0.52; 95% CI 0.33-0.84), use of angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers (OR 1.35; 95% CI 1.05-1.75), colloid infusion during surgery (OR 1.11; 95% CI 1.06-1.18), and postoperative 2-day C-reactive protein (OR 1.05; 95% CI 1.01-1.09). Postoperative AKI was associated with prolonged length of hospital stay.



Postoperative AKI is common in patients undergoing esophageal surgery for cancer. Closer evaluation and monitoring in patients with risk factors for AKI may be warranted.

title: Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement
abstract: Systematic reviews should build on a protocol that describes the rationale, hypothesis, and planned methods of the review; few reviews report whether a protocol exists. Detailed, well-described protocols can facilitate the understanding and appraisal of the review methods, as well as the detection of modifications to methods and selective reporting in completed reviews. We describe the development of a reporting guideline, the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Protocols 2015 (PRISMA-P 2015). PRISMA-P consists of a 17-item checklist intended to facilitate the preparation and reporting of a robust protocol for the systematic review. Funders and those commissioning reviews might consider mandating the use of the checklist to facilitate the submission of relevant protocol information in funding applications. Similarly, peer reviewers and editors can use the guidance to gauge the completeness and transparency of a systematic review protocol submitted for publication in a journal or other medium.

title: World incidence of AKI: a meta-analysis.
abstract: The burden of AKI around the globe has not been systematically examined.



A systematic review (2004-2012) of large cohort studies was conducted to estimate the world incidence of AKI and its stages of severity and associated mortality, and to describe geographic variations according to countries, regions, and their economies. AKI definitions were reclassified according to the Kidney Disease Improving Global Outcomes (KDIGO) staging system. Random-effects model meta-analyses and meta-regressions were used to generate summary estimates and explore sources of heterogeneity.



There were 312 studies identified (n=49,147,878) , primarily in hospital settings. Most studies originated from North America, Northern Europe, and Eastern Asia, from high-income countries, and from nations that spent ≥5% of the gross domestic product on total health expenditure. Among the 154 studies (n=3,585,911) that adopted a KDIGO-equivalent AKI definition, the pooled incidence rates of AKI were 21.6% in adults (95% confidence interval [95% CI], 19.3 to 24.1) and 33.7% in children (95% CI, 26.9 to 41.3). The pooled AKI-associated mortality rates were 23.9% in adults (95% CI, 22.1 to 25.7) and 13.8% in children (95% CI, 8.8 to 21.0). The AKI-associated mortality rate declined over time, and was inversely related to income of countries and percentage of gross domestic product spent on total health expenditure.



Using the KDIGO definition, 1 in 5 adults and 1 in 3 children worldwide experience AKI during a hospital episode of care. This analysis provides a platform to raise awareness of AKI with the public, government officials, and health care professionals.

title: The impact of pre-operative serum creatinine on short-term outcomes after liver resection.
abstract: The aim of the present study was to determine whether raised pre-operative serum creatinine increased the risk of renal failure after liver resection.



Data were studied from 1535 consecutive liver resections. Outcomes in patients with pre-operative creatinine </=124 micromol/l (Group 1) were compared with those with pre-operative creatinine >/=125 micromol/l (Group 2).



The median age of the 1446 (94.3%) patients resected in Group 1 was 62 years compared with 67 years in the 88 (5.7%) patients in Group 2 (P < 0.0001). Similarly this latter group had double the number of patients who were American Society of Anesthesiologists (ASA) III or IV (34.1% vs. 15.2%, P= 0.00004). Overall, the incidence of post-operative renal failure requiring haemofiltration was low (0.9%) but significantly more in Group 2 patients (5.7% vs. 0.6, P= 0.0007). In addition, patients in Group 2 were more likely to suffer acute kidney injury post-operatively (18.2% vs. 4.3%, P < 0.0001). Patients with acute kidney injury had significantly higher blood loss. Although there was no difference in mortality, patients in Group 2 had higher post-operative morbidity (37.5%) than Group 1 (21.7%, P= 0.0006), with the incidence of cardiorespiratory complications being higher in Group 2 (25.9% vs. 8.9%, P= 0.0025).



After liver resection, renal failure is rare but patients with an elevated creatinine pre-operatively are at an increased risk of both renal and non-renal complications.

title: Risk of AKI with gentamicin as surgical prophylaxis.
abstract: In 2009, the Scottish government issued a target to reduce Clostridium difficile infection by 30% in 2 years. Consequently, Scottish hospitals changed from cephalosporins to gentamicin for surgical antibiotic prophylaxis. This study examined rates of postoperative AKI before and after this policy change. The study population comprised 12,482 adults undergoing surgery (orthopedic, urology, vascular, gastrointestinal, and gynecology) with antibiotic prophylaxis between October 1, 2006, and September 30, 2010 in the Tayside region of Scotland. Postoperative AKI was defined by the Kidney Disease Improving Global Outcomes criteria. The study design was an interrupted time series with segmented regression analysis. In orthopedic patients, change in policy from cefuroxime to flucloxacillin (two doses of 1 g) and single-dose gentamicin (4 mg/kg) was associated with a 94% increase in AKI (P=0.04; 95% confidence interval, 93.8% to 94.3%). Most patients who developed AKI after prophylactic gentamicin had stage 1 AKI, but some patients developed persistent stage 2 or stage 3 AKI. The antibiotic policy change was not associated with a significant increase in AKI in the other groups. Regardless of antibiotic regimen, however, rates of AKI were high (24%) after vascular surgery, and increased steadily after gastrointestinal surgery. Rates could only be ascertained in 52% of urology patients and 47% of gynecology patients because of a lack of creatinine testing. These results suggest that gentamicin should be avoided in orthopedic patients in the perioperative period. Our findings also raise concerns about the increasing prevalence of postoperative AKI and failures to consistently measure postoperative renal function.

title: Incidence, risk factors, and outcomes of perioperative acute kidney injury in noncardiac and nonvascular surgery.
abstract: The aim of this study was to determine the incidence rate, identify the risk factors, and describe the clinical outcome of perioperative acute kidney injury (AKI) in patients undergoing noncardiac, nonvascular surgery (NCS).



A total of 1,200 adult consecutive patients undergoing NCS were prospectively evaluated. Patients with pre-existing renal dysfunction were excluded. The primary outcome of this study was perioperative AKI defined by the RIFLE (risk, injury, failure, loss of function, and end-stage kidney disease) criteria.



Eighty-one patients (6.7%) met the AKI criteria. Multivariate analysis identified age, diabetes, revised cardiac risk index, and American Society of Anesthesiologists physical status as independent predictors of AKI. Patients with AKI had more cardiovascular (33.3% vs 11.3%, P < .001) complications and a higher in-hospital mortality rate (6.1% vs 0.9%, P = .003) compared with patients without AKI.



Several preoperative predictors are found to be associated with AKI after NCS. Perioperative AKI is an independent risk factor for outcome after NCS.

title: Identifying risk factors for renal failure and myocardial infarction following colorectal surgery.
abstract: The development of acute renal failure and myocardial infarction (MI) following colectomy prolongs recovery and is associated with worse outcomes. The purpose of this study is to identify perioperative factors that predispose patients to an adverse cardiac or renal complication.



We conducted a retrospective review of colectomies from 2001 to 2009. Patients were evaluated based upon the electronic inpatient record and followed to determine the incidence of acute renal failure (creatinine elevation over 50% of baseline) and myocardial injury.



A total of 339 inpatient records were reviewed, of which 134 were female (40%) and 205 male (60%). The mean age was 61.96 ± 16.2 years with 39.5% right hemicolectomies, 22.7% sigmoidectomy, 13.9% Left hemicolectomy, 11.5% total abdominal colectomy, and 6.2% for ileocectomy and transverse colectomy. Within the cohort, 13.9% had baseline renal insufficiency (Cr > 1.4), 7.1% sustained anastomotic leak, 23.9% required postoperative intubation, 15% sustained postoperative sepsis, 11.2% postoperative MI, and 5% clinically significant acidosis. Excluding patients with an anastomotic leak, postoperative intubation, and sepsis, we found that the need for blood product transfusion was associated with postoperative acute renal failure (OR= 7.15 [2.4-20.7]). Preoperative creatinine > 1.5, limited functional capacity, and preoperative systolic blood pressure < 90 mm Hg were all associated with increased MI rates (OR= 15.7 [3.6-66.8], 9.5 [2.1-42.2], 12.0 [5.523-26.072], and 40.6 [1.7-968], respectively).



This study demonstrates that several potentially modifiable preoperative and intraoperative factors exist that predispose patients to postoperative cardiac and renal dysfunction in the absence of major surgical complications.

title: Acute kidney injury network staging in geriatric postoperative acute kidney injury patients: shortcomings and improvements.
abstract: The incidence of acute kidney injury (AKI) is rising, particularly among the elderly. However, the optimal risk stratification scheme for these patients is unknown. The Acute Kidney Injury Network (AKIN) classification application in geriatric patients has not been previously confirmed.



In this multicenter study, elderly patients (>65 years old) who had major surgery and were admitted to ICUs between January 1, 2002 and December 31, 2008 were recruited and grouped according to the AKIN creatinine criteria. The utility of the AKIN criteria for the prediction of in-hospital mortality was determined using Cox proportional hazard regression modeling.



A total of 4,240 eligible patients were identified and separated into "non-AKI" (n = 3,259), AKIN 1 (n = 582), AKIN 2 (n = 78), and AKIN 3 groups (n = 321). Cox proportional hazard regression analysis revealed that the AKIN 3 group has a significantly higher hospital mortality compared with the non-AKI group (hazard ratio [HR] 3.19, 95% CI 2.16 to 4.71; p < 0.001); the AKIN 1 (p = 0.611) and AKIN 2 (p = 0.104) groups have no significant differences compared with the non-AKI group. After excluding patients who received hemodialysis 1 week postoperatively, the AKIN 2 group predicted a significantly higher risk of hospital mortality compared with the non-AKI group (HR 2.31; p = 0.008).



This is the first study to demonstrate the poor applicability of the AKIN classification in the prediction of in-hospital mortality in geriatric postoperative AKI patients. Consideration of late dialysis status may enhance the discriminative power of AKIN in this specific population.

title: The incidence and risk factors of acute kidney injury after hepatobiliary surgery: a prospective observational study
abstract: BackgroundAlthough intraperitoneal surgery is a major operation associated with postoperative acute kidney injury (AKI), the incidence, risk factors, and long-term renal outcome are not well known. We aimed to determine the risk factors and 6 months renal outcome in patients with clinical or subclinical AKI after hepatobiliary surgery. We also assessed the validity of urine neutrophil gelatinase-associated lipocalin (NGAL) in the early detection of AKI or prediction of renal outcome.MethodsThis prospective observational study enrolled patients with normal renal function who underwent hepatobiliary surgeries. Urine and serum samples were collected for NGAL measurement.ResultsAmong 131 patients, 10 (7.6%) developed postoperative AKI. Urine NGAL at 12 h postsurgery was the most predictive parameter for the diagnosis of AKI (cutoff, 92.85 ng/mL). With the cutoff value, subclinical AKI was diagnosed in 42 (32.1%) patients. Patients with clinical AKI and those with subclinical AKI were assigned to the AKI group. The AKI group had significantly higher model for end-stage liver disease and sodium (MELD-Na) score, lower albumin level, and longer hospital stay after surgery than the non-AKI group. Older age and higher MELD-Na score were independent risk factors for the development of postoperative AKI. At 6 months postsurgery, the estimated glomerular filtration rate (eGFR) in the AKI group was significantly lower than that in the non-AKI group, although the baseline eGFR was not different. In multiple linear regression analysis, the maximum urine NGAL level during 24 h postsurgery, intraoperative fluid balance, and having liver transplantation were significantly associated with a poor 6 months renal outcome.ConclusionUrine NGAL was useful in the early diagnosis of postoperative AKI as well as in predicting the 6 months renal outcome after hepatobiliary surgery. A considerable proportion of patients developed subclinical AKI, and these patients showed worse renal outcome compared with the non-AKI group.

title: The duration of postoperative acute kidney injury is an additional parameter predicting long-term survival in diabetic veterans.
abstract: Acute kidney injury (AKI) is primarily defined and staged according to the magnitude of the rise in serum creatinine. Here we sought to determine if the duration of AKI adds additional prognostic information above that from the magnitude of injury alone. We prospectively studied 35,302 diabetic patients from 123 Veterans Affairs Medical Centers undergoing their first noncardiac surgery. The main outcome was long-term mortality in those who survived the index hospitalization. AKI was stratified by magnitude according to AKI Network stages and by the duration (short (less than 2 days), medium (3-6 days) or long (7 days or more)). Overall, 17.8% of patients experienced at least stage 1 AKI or greater following surgery. Both the magnitude and duration of AKI were significantly associated with long-term survival in a dose-dependent manner. Within each stage, longer duration of AKI was significantly associated with a graded higher rate of mortality. However, within each of the duration categories, the stage was not associated with mortality. When considered separately in multivariate analyses, both a higher stage and duration were independently associated with increased risk of long-term mortality. Hence, the duration of AKI adds additional information to predict long-term mortality.

title: Renal function after low central venous pressure-assisted liver resection: assessment of 2116 cases.
abstract: Low central venous pressure (LCVP)-assisted hepatectomy is associated with decreased blood loss and lower transfusion rates. Concerns about its impact on renal function have prevented widespread application. This study was conducted to review the dynamics of renal function after LCVP-assisted hepatectomy.



A retrospective analysis of a prospective surgical database was carried out. Estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease (MDRD) equation. The RIFLE (risk-injury-failure-loss-end-stage) criteria were used to define postoperative biochemical acute kidney injury (bAKI). Occurrences of clinically relevant AKI (cAKI) were identified in the study center postoperative database.



During the period 2003-2012, 2116 LCVP-assisted hepatectomies were performed. The median patient age was 61 years [interquartile range (IQR): 51-70 years] and 51% of patients were male. The median number of resected segments was two; resections involved from one to four segments. Median estimated blood loss was 300 ml (IQR: 200-600 ml). Rates of morbidity and 90-day mortality were 21% and 2%, respectively. Low baseline eGFR (<90 ml/min) was seen in 84% of patients; 29% of patients had eGFR of <30 ml/min. Postoperative bAKI was seen in 17% (n = 350) of patients. Biochemical AKI with low eGFR was seen in 336 patients, representing 16% of the whole cohort; 13% of patients had been at risk, 2% experienced injury and 1% experienced failure. Kidney function had normalized at discharge in 159 of these patients. Nine patients (<1%) developed postoperative cAKI.



The majority of patients in the study cohort had low baseline eGFR. Biochemical alterations in eGFR are transient in the vast majority of patients after LCVP-assisted hepatectomy and their clinical impact is limited. The present data suggest that clinically relevant renal dysfunction is a very uncommon event in patients undergoing LCVP-assisted liver resection.

title: Incidence, Predictive Factors, and Clinical Outcomes of Acute Kidney Injury after Gastric Surgery for Gastric Cancer
abstract: Postoperative acute kidney injury (AKI), a serious surgical complication, is common after cardiac surgery; however, reports on AKI after noncardiac surgery are limited. We sought to determine the incidence and predictive factors of AKI after gastric surgery for gastric cancer and its effects on the clinical outcomes.  We conducted a retrospective study of 4718 patients with normal renal function who underwent partial or total gastrectomy for gastric cancer between June 2002 and December 2011. Postoperative AKI was defined by serum creatinine change, as per the Kidney Disease Improving Global Outcomes guideline.  Of the 4718 patients, 679 (14.4%) developed AKI. Length of hospital stay, intensive care unit admission rates, and in-hospital mortality rate (3.5% versus 0.2%) were significantly higher in patients with AKI than in those without. AKI was also associated with requirement of renal replacement therapy. Multivariate analysis revealed that male gender; hypertension; chronic obstructive pulmonary disease; hypoalbuminemia (<4 g/dl); use of diuretics, vasopressors, and contrast agents; and packed red blood cell transfusion were independent predictors for AKI after gastric surgery. Postoperative AKI and vasopressor use entailed a high risk of 3-month mortality after multiple adjustments.  AKI was common after gastric surgery for gastric cancer and associated with adverse outcomes. We identified several factors associated with postoperative AKI; recognition of these predictive factors may help reduce the incidence of AKI after gastric surgery. Furthermore, postoperative AKI in patients with gastric cancer is an important risk factor for short-term mortality.

title: Development and Validation of a Prediction Score for Postoperative Acute Renal Failure Following Liver Resection
abstract: To develop and validate a score to predict postoperative acute renal failure (ARF) after liver resection. Postoperative ARF after major surgery is associated with morbidity and mortality. Early identification of patients at risk of ARF is important in order to provide protective kidney treatment. Postoperative ARF was prospectively assessed in consecutive patients undergoing liver resection. In randomly selected two-third of the total number of patients, multivariate logistic regression analysis was used to develop a new prediction score (including a full and a reduced model), based on the preoperative parameters of age, gender, preexisting chronic renal dysfunction, cardiovascular disease, diabetes, bilirubin, and alanine aminotransferase (ALT) levels. In the remaining last third of the patients, the new score was validated by calibrating the accuracy of the score (ClinicalTrials.gov NCT 00743132). Postoperative ARF occurred in 15.1% (86 of 569 consecutive patients) from 2002 to 2007 and was highly associated with mortality (22.5% vs. 0.8% without ARF, P < 0.001). In the 380 (two-third of the population) patients selected for the development of the prediction score, preoperatively elevated ALT, preexisting cardiovascular disease, chronic renal failure, and diabetes were the strongest predictors of ARF. Validating the full prediction model (0–22 points) to the remaining 189 patients (one-third of the population), the risk could be predicted accurately (mean predicted risk of 11.5% vs. an observed risk of 14.8%) without significant differences between predicted and observed risks across different risk categories (P = 0.98). Prediction with the reduced model including the 4 strongest predictors (0–7 points) was almost as accurate as with the full model (11.4% predicted vs. 14.8% observed) and also without significant differences across different risk categories (P = 0.75). The new prediction score (the full as well as the reduced model) accurately predicted postoperative ARF after liver resection. The use of these scores allows early identification of patients at high risk of ARF, and may support decision making for protective kidney interventions perioperatively.

title: Acute Kidney Injury after Major Abdominal Surgery: A Retrospective Cohort Analysis
abstract: We analyzed the incidence, risk factors, and prognosis of acute kidney injury (AKI) in a cohort of patients undergoing major abdominal surgery.  A total of 450 patients were retrospectively studied. AKI was defined by an increase in serum creatinine (SCr) ≥ 0.3 mg/dl or by an increase in SCr ≥ 50% and/or by a decrease in urine output to 0.5 ml/kg/hour for 6 hours, in the first 48 hours after surgery. Logistic regression method was used to determine predictors of AKI and in-hospital mortality. A two-tailed P value <0.05 was considered significant.  One hundred one patients (22.4%) had postoperative AKI. Age (adjusted odds ratio (OR) 1.02, 95% confidence interval (CI) 1.01–1.05), nonrenal Revised Cardiac Risk Index score (adjusted OR 1.9, 95% CI 1.3–3.1, P = 0.003), intraoperative erythrocytes transfusions (adjusted OR 2.2, 95% CI 1.4–3.5, P <.0001), and nonrenal Simplified Acute Physiology Score II (adjusted OR 1.03, 95% CI 1.01–1.06, P = 0.0191) were associated with postoperative AKI. AKI was associated with increased in-hospital mortality (20.8% versus 2.3%, P <.0001; unadjusted OR 11.2, 95% CI 4.8–26.2, P <.0001; adjusted OR 3.7, 95% CI 1.2–11.7, P = 0.024).  AKI was common in patients undergoing major abdominal surgery and was associated with in-hospital mortality.

title: Acute kidney injury in major gynaecological surgery: an observational study
abstract: To assess the prevalence, outcomes and cost associated with acute kidney injury (AKI) defined by consensus risk, injury, failure, loss, and end‐stage kidney (RIFLE) criteria after gynaecologic surgery.

title: Acute Kidney Injury After Major Surgery: A Retrospective Analysis of Veterans Health Administration Data.
abstract: Few trials of acute kidney injury (AKI) prevention after surgery have been conducted, and most observational studies focus on AKI following cardiac surgery. The frequency of, risk factors for, and outcomes after AKI following other types of major surgery have not been well characterized and may present additional opportunities for trials in AKI.



Observational cohort study.



3.6 million US veterans followed up from 2004 to 2011 for the receipt of major surgery (cardiac; general; ear, nose, and throat; thoracic; vascular; urologic; and orthopedic) and postoperative outcomes.


FACTORS
Demographics, health characteristics, and type of surgery.



Postoperative AKI defined by the KDIGO creatinine criteria, postoperative length of stay, end-stage renal disease, and mortality.



Postoperative AKI occurred in 11.8% of the 161,185 major surgery hospitalizations (stage 1, 76%; stage 2, 15%, stage 3 [without dialysis], 7%; and AKI requiring dialysis, 2%). Cardiac surgery had the highest postoperative AKI risk (relative risk [RR], 1.22; 95% CI, 1.17-1.27), followed by general (reference), thoracic (RR, 0.92; 95% CI, 0.87-0.98), orthopedic (RR, 0.70; 95% CI, 0.67-0.73), vascular (RR, 0.68; 95% CI, 0.64-0.71), urologic (RR, 0.65; 95% CI, 0.61-0.69), and ear, nose, and throat (RR, 0.32; 95% CI, 0.28-0.37) surgery. Risk factors for postoperative AKI included older age, African American race, hypertension, diabetes mellitus, and, for estimated glomerular filtration rate < 90mL/min/1.73m(2), lower estimated glomerular filtration rate. Participants with postoperative AKI had longer lengths of stay (15.8 vs 8.6 days) and higher rates of 30-day hospital readmission (21% vs 13%), 1-year end-stage renal disease (0.94% vs 0.05%), and mortality (19% vs 8%), with similar associations by type of surgery and more severe stage of AKI relating to poorer outcomes.



Urine output was not available to classify AKI; cohort included mostly men.



AKI was common after major surgery, with similar risk factor and outcome associations across surgery type. These results can inform the design of clinical trials in postoperative AKI to the noncardiac surgery setting.

title: Epidural analgesia and perioperative kidney function after major liver resection
abstract: Epidural analgesia (EDA) is a common analgesia regimen in liver resection, and is accompanied by sympathicolysis, peripheral vasodilatation and hypotension in the context of deliberate intraoperative low central venous pressure. This associated fall in mean arterial pressure may compromise renal blood pressure autoregulation and lead to acute kidney injury (AKI). This study investigated whether EDA is a risk factor for postoperative AKI after liver surgery.

title: Association of Intraoperative Hypotension with Acute Kidney Injury after Elective Noncardiac Surgery
abstract: Intraoperative hypotension (IOH) may be associated with postoperative acute kidney injury (AKI), but the duration of hypotension for triggering harm is unclear. The authors investigated the association between varying periods of IOH with mean arterial pressure (MAP) less than 55, less than 60, and less than 65 mmHg with AKI. The authors conducted a retrospective cohort study of 5,127 patients undergoing noncardiac surgery (2009 to 2012) with invasive MAP monitoring and length of stay of 1 or more days. Exclusion criteria were preoperative MAP less than 65 mmHg, dialysis dependence, urologic surgery, and surgical duration less than 30 min. The primary exposure was IOH. The primary outcome was AKI (50% or 0.3 mg/dl increase in creatinine) during the first 2 postoperative days. Multivariable logistic regression was used to model the exposure–outcome relationship. AKI occurred in 324 (6.3%) patients and was associated with MAP less than 60 mmHg for 11 to 20 min and MAP less than 55 mmHg for more than 10 min in a graded fashion. The adjusted odds ratio of AKI for MAP less than 55 mmHg was 2.34 (1.35 to 4.05) for 11- to 20-min exposure and 3.53 (1.51 to 8.25) for more than 20 min. For MAP less than 60 mmHg, the adjusted odds ratio for AKI was 1.84 (1.11 to 3.06) for 11- to 20-min exposure. In this analysis, postoperative AKI is associated with sustained intraoperative periods of MAP less than 55 and less than 60 mmHg. This study provides an impetus for clinical trials to determine whether interventions that promptly treat IOH and are tailored to individual patient physiology could help reduce the risk of AKI.

title: Acute renal failure in critically ill surgical patients: persistent lethality despite new modes of renal replacement therapy.
abstract: Despite improved resuscitation and sepsis care, acute renal failure (ARF) remains common in critically ill surgical patients. New methods of renal replacement therapy (RRT) are being used in surgical intensive care units (SICUs), including high-flux hemodialysis (HD) and continuous RRT (CRRT). RRT is being used increasingly early in the course of ARF, but data are scant to suggest that mortality is improved. Consequently, we determined whether outcomes were improved with CRRT in SICU patients, and hypothesized that CRRT lowers mortality for patients with ARF.



Patients who developed ARF (acute increase in serum creatinine concentration >or=2.4 mg/dL) in the SICU from 1993 to 2004 were identified. Data collected prospectively included year of admission, age, gender, Acute Physiology and Chronic Health Evaluation (APACHE) III score, cumulative multiple organ dysfunction score and its individual components, cumulative nonrenal organ dysfunction score, and need for RRT. Patients were stratified January 1994 to January 2001 (pre-CRRT) and February 2001 to December 2004 (post-CRRT). The primary endpoint was mortality.



Among 8,505 SICU patients, 530 (6.2%) developed ARF. Three hundred and eleven patients were treated pre-CRRT and 219 thereafter. Female patients comprised 35% of ARF patients. The mean age was 69 years +/- 2 years, and the mean APACHE III score was 81 +/- 1 point for ARF patients. HD was performed in 15.6% of ARF patients before 2001 and 5.5% of ARF patients in 2001 and thereafter. CRRT was performed in 20.1% of ARF patients in 2001 and thereafter. Overall mortality for ARF patients was 45% (APACHE III normative predicted mortality: 55%) with no difference over time (pre-CRRT = 46.3%, post-CRRT = 45.2%, p = 0.86). Patients who required RRT had a mean APACHE III score of 91 +/- 1 point, with 61% mortality (predicted mortality: 67%), with no difference over time. Independent predictors of mortality overall and for ARF patients included age and the magnitude of renal, cardiovascular, hepatic, and neurologic dysfunction. In comparison with CRRT, HD was associated with a decreased risk of death.



Despite more frequent RRT and the use of CRRT, the mortality of ARF in critically ill surgical patients remains high because of nonrenal organ dysfunction. Considering that ARF-related mortality was decreased by intermittent HD, and that intermittent RRT is less costly, patients who need RRT should be treated preferentially with HD.

title: Clinical accuracy of RIFLE and Acute Kidney Injury Network (AKIN) criteria for acute kidney injury in patients undergoing cardiac surgery
abstract: IntroductionThe RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for acute kidney injury (AKI) was recently modified by the Acute Kidney Injury Network (AKIN). The two definition systems differ in several aspects, and it is not clearly determined which has the better clinical accuracy.MethodsIn a retrospective observational study we investigated 4,836 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass from 2005 to 2007 at Mayo Clinic, Rochester, MN, USA. AKI was defined by RIFLE and AKIN criteria.ResultsSignificantly more patients were diagnosed as AKI by AKIN (26.3%) than by RIFLE (18.9%) criteria (P < 0.0001). Both definitions showed excellent association to outcome variables with worse outcome by increased severity of AKI (P < 0.001, all variables). Mortality was increased with an odds ratio (OR) of 4.5 (95% CI 3.6 to 5.6) for one class increase by RIFLE and an OR of 5.3 (95% CI 4.3 to 6.6) for one stage increase by AKIN. The multivariate model showed lower predictive ability of RIFLE for mortality. Patients classified as AKI in one but not in the other definition set were predominantly staged in the lowest AKI severity class (9.6% of patients in AKIN stage 1, 2.3% of patients in RIFLE class R). Potential misclassification of AKI is higher in AKIN, which is related to moving the 48-hour diagnostic window applied in AKIN criteria only. The greatest disagreement between both definition sets could be detected in patients with initial postoperative decrease of serum creatinine.ConclusionsModification of RIFLE by staging of all patients with acute renal replacement therapy (RRT) in the failure class F may improve predictive value. AKIN applied in patients undergoing cardiac surgery without correction of serum creatinine for fluid balance may lead to over-diagnosis of AKI (poor positive predictive value). Balancing limitations of both definition sets of AKI, we suggest application of the RIFLE criteria in patients undergoing cardiac surgery.

title: Determinants of postoperative acute kidney injury
abstract: IntroductionDevelopment of acute kidney injury (AKI) during the perioperative period is associated with increases in morbidity and mortality. Our aim was to evaluate the incidence and determinants of postoperative AKI after major noncardiac surgery in patients with previously normal renal function.MethodsThis retrospective cohort study was carried out in the multidisciplinary Post-Anaesthesia Care Unit (PACU) with five intensive care beds. The study population consisted of 1166 patients with no previous renal insufficiency who were admitted to these intensive care unit (ICU) beds over 2 years. After admission patients were followed for the development of AKI, defined as proposed by The Acute Kidney Injury Network (increment of serum creatinine [greater than or equal to] 0.3 mg/dL or 50% from baseline within 48 hours or urine output < 0.5 mL/kg/hr for > 6 hours despite fluid resuscitation when applicable). Patient preoperative characteristics, intraoperative management and outcome were evaluated for associations with acute kidney injury using an univariate and multiple logistic regression model. total of 1597 patients were admitted to the PACU and of these, 1166 met the inclusion criteria. Eighty-seven patients (7.5%) met AKI criteria. Univariate analysis identified age, American Society of Anesthesiologists (ASA) physical status, emergency surgery, high risk surgery, ischemic heart disease, congestive heart disease and Revised Cardiac Risk Index (RCRI) score as independent preoperative determinants for AKI in the postoperative period. Multivariate analysis identified ASA physical status, RCRI score, high risk surgery and congestive heart disease as preoperative determinants for AKI in the postoperative period. Patients that developed AKI had higher Simplified Acute Physiology Score (SAPS) II and Acute Physiology and Chronic Health Evaluation (APACHE) II, higher PACU length of stay (LOS), higher PACU mortality, higher hospital mortality and higher mortality at 6 months follow-up. AKI was an independent risk factor for hospital mortality (OR 3.12, 95% CI 1.41 to 6.93, P = 0.005).ConclusionsThis study shows that age, emergency and high risk surgery, ischemic heart disease, congestive heart disease, ASA physical status and RCRI score were considered risk factors for the development of AKI, in patients needing intensive care after surgery. AKI has serious impact on PACU length of stay and mortality. AKI was an independent risk factor for hospital mortality.

title: Experience with 1509 patients undergoing thoracoabdominal aortic operations.
abstract: The purpose of this study was to retrospectively identify variables associated with early death and postoperative complications in patients undergoing thoracoabdominal aortic operations.



The data on 1509 patients who underwent 1679 thoracoabdominal aortic repairs between 1960 and 1991 were retrospectively reviewed. The median age was 66 years (range 1.5 years to 86 years), and aortic dissection was present in 276 (18%) patients. The extent of the first repair performed included 378 (25%) type I (proximal descending to upper abdominal aorta), 442 (29%) type II (proximal descending aorta to below the renal arteries), 343 (23%) type III (distal descending and abdominal aorta), and 346 (23%) type IV (most of the abdominal aorta). The median total aortic clamp time was 43 minutes.



The 30-day survival rate was 92% (1386/1509) for the 30-year period. On multivariate analysis the preoperative and operative variables associated with death included (p < 0.05) increasing age, preoperative creatinine level, concurrent proximal aortic aneurysms, coronary artery disease, chronic lung disease, and total aortic clamp time. When the postoperative variables were also included in the stepwise logistic regression model, then in addition, cardiac complications, stroke, kidney failure, and gastrointestinal hemorrhage became significant (p < 0.05). The overall incidence of paraplegia or paraparesis was 16% (234/1509). By use of stepwise logistic regression analysis, the significant predictors (p < 0.05) of paraplegia or paraparesis developing were total aortic clamp time, extent of aorta repaired, aortic rupture, patient age, proximal aortic aneurysm, and history of renal dysfunction. Kidney failure (postoperative creatinine level > 3 mg/dl or dialysis) occurred in 18% (269/1509) of patients; dialysis was required in 9% (136/1509). Gastrointestinal complications manifested in 7% (101/1509) of patients.



Although the survival rate has improved, paraplegia/paraparesis and kidney failure continue to be vexing problems that require further research.