Clinical trial NCT00689091: Bispectral Index (BIS) Versus Electronic Alerts in the Prevention of Anesthesia Awareness: the Michigan Awareness Control Study
Official title: A Prospective, Randomized, Controlled Trial Comparing Bispectral Index Monitoring to Electronic Alerts for Prevention of Awareness During Anesthesia in the General Population
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Awareness During General Anesthesia
Keywords: Awareness
BIS Monitor
electronic alerts
minimum
alveolar
concentration
Lead sponsor: University of Michigan
Sponsor class: OTHER
Collaborators: name: Foundation for Anesthesia Education and Research
name: American Society of Anesthesiologists
name: Washington University School of Medicine
name: University of Chicago
name: University of Manitoba
First posted: 2008-06-03
Enrollment: 22185
Sex: ALL
Minimum age (years): 18
Maximum age (years): 100
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: PREVENTION

Brief summary: Awareness during anesthesia is a problem receiving increased attention by patients, clinicians, and the general public. The incidence of intraoperative awareness has been reported to be between 1-2/1000 cases, but recent data suggest that this may be an overestimate. The Bispectral Index (BIS) Monitor is an electroencephalographic method of assessing depth of anesthesia that has been shown in one study to reduce the incidence of awareness during anesthesia in the high-risk population (Myles et al, 2004). In the study of Myles et al, the number needed to treat (NNT) in order to prevent one case of awareness in the high-risk population was 138, with an associated cost of approximately US$2200. Since the NNT and the associated cost of treatment would be much higher in the general population, the efficacy of the BIS monitor in preventing awareness in all anesthetized patients needs to be clearly established. Furthermore, recent data suggest that the BIS may not be useful in the high-risk population. The investigators propose a prospective, randomized, controlled trial comparing the BIS monitor to electronic alerts based on non-electroencephalographic gauges of anesthetic depth.

Detailed description: Electronic alerts have been developed and employed at our institution and have been shown to increase compliance with both clinical and administrative tasks (O'Reilly et al, 2006; Kheterpal et al, 2007). The investigators have developed electronic alerts for the purpose of informing the clinician of potentially insufficient anesthesia based on minimum alveolar concentration (MAC). The algorithm is as follows:

* Every 5 minutes the alerting system checks every active case in our operating rooms. It takes approximately 1 second for this scan of all active cases to occur.
* Conditions for an "active case" are:

  1. data capture is possible (i.e., not a paper record)
  2. data capture is active (i.e., "patient in room" has been electronically entered and end-tidal \[Et\] CO2 is detected)
  3. case has been identified as a general anesthetic
  4. "anesthesia induction end" has already been documented
  5. request for recovery room bed or transport to an intensive care unit has not been documented
  6. surgical dressing completion has not been documented
* The alerting system checks the most recent value (within a specified time period) of:

  1. Et Sevoflurane (MAC=2.0)
  2. Et Isoflurane (MAC=1.2)
  3. Et Desflurane (MAC=6)
  4. Et Nitrous Oxide (MAC=105) and compares it to the MAC of each agent. It adds the resulting MAC values together for "current total MAC."
* The system then checks for a charted propofol infusion in mcg/kg/min and divides by 150, assuming that 150 mcg/kg/min is "1.0 MAC" for propofol. The analogous concept of MAC for propofol is "Cp50"- the plasma or blood concentrations at which 50% of patients do not move in response to a noxious stimulus. Since the investigators do not have the technology at our institution to calculate Cp50 or Cp50-awake, the investigators have chosen the above propofol dose as an initial value based on clinical experience. The resultant MAC equivalent is added to current total MAC.
* The system next checks for a dexmedetomidine infusion with a rate of 0.2 mcg/kg/hour or greater. If present, it multiplies the current total inhalational MAC by 2, as dexmedetomidine can reduce MAC by 50%.
* At this point, the "current total MAC" is defined as: Et Sevo /2 + Et Iso /1.2 + Et Des/6 + Et Nitrous /105 + propofol rate (in mcg/kg/min)/150. If dexmedetomidine is \>0.2 mcg/kg/hour, inhalational MAC is multiplied by 2.
* If this total mac \< 0.50, it checks to see if a bolus of propofol, midazolam, etomidate, or thiopental has been given in the preceding 10 minutes.
* It alerts the clinician signed into the case within 30-60 seconds if total age-adjusted MAC \< 0.50 AND no bolus has been documented in the last 10 minutes.

This will be the protocol in the MAC-guided group. In the BIS-guided group an electronic alert will be sent if the BIS value is \>60. If an alert is triggered, the clinician electronically signed into the case receives an alphanumeric page stating "Potentially insufficient anesthesia, please check vaporizers and intravenous lines."

The investigators are collaborating with Washington University, the University of Chicago, and the University of Mannitoba, who will also be testing a MAC-based protocol in comparison to the BIS.

Eligibility criteria: Inclusion Criteria:

* At least 18 years of age, English-speaking, available for follow-up interview at one month.

Exclusion Criteria:

* Pre-existing neurologic or neuropsychiatric condition, surgical manipulation around forehead, not available for follow-up interview.

Primary outcomes:
measure: The Percentage of Incidences With Explicit Recall in the BIS Versus MAC Alert Groups.
timeFrame: Outcome of awareness is assessed 30-days after the operation
Secondary outcomes:
measure: Number of Participants With Dreams During Anesthesia Compared Between MAC or BIS Monitoring
timeFrame: During surgery (45 minutes - 18 hours), measured based on 30 day interviews
measure: Percentage of Cases With Electronic Alerts
timeFrame: During surgery: (45 minutes - 18 hours)
measure: Overall Use of Anesthetics Comparing the BIS to MAC Alerts.
timeFrame: During surgery (45 minutes - 18 hours)
measure: Time Till Discharge Readiness
timeFrame: During recovery room stay: 30 minutes to 6 hours
measure: Number of Participants Without Nausea or Vomiting
timeFrame: During recovery room stay: 30 minutes to 6 hours
measure: Comparison of the Prospective and Retrospective Approaches to the Study Awareness Incidence.
timeFrame: 30 days after surgery
Other outcomes:
measure: Relationship Between BIS Values and Hemodynamic Parameters.
timeFrame: Outcome of hemodynamic stability is assessed
measure: The Relationship Between Cumulative Deep Hypnotic Time, Anesthetic Doses, and Mortality.
timeFrame: Outcome of mortality is assessed
measure: Predictors of Post-traumatic Stress Disorder Based on the Type of Awareness Event.
timeFrame: Outcome of post-traumatic stress disorder is assessed with the covariate of awareness
measure: Anesthetic Induction Doses, Hypotension, and BIS Values.
timeFrame: Outcome of hypotension in relationship to induction doses and BIS values will be assessed
measure: Meta-Analysis of Awareness Events in Conjunction With the BAG-RECALL Study Based at Washington University.
timeFrame: Outcome of awareness is assessed
measure: Incidence of Post-traumatic Stress Disorder.
timeFrame: NEED VALUE HERE
Locations:
city: Ann Arbor
country: United States
facility: University of Michigan Medical School, University Hospital
state: Michigan
Study officials:
affiliation: University of Michigan
name: George A. Mashour, M.D., Ph.D.
role: PRINCIPAL_INVESTIGATOR
References:
citation: Vance JL, Shanks AM, Woodrum DT. Intraoperative bispectral index monitoring and time to extubation after cardiac surgery: secondary analysis of a randomized controlled trial. BMC Anesthesiol. 2014 Sep 18;14:79. doi: 10.1186/1471-2253-14-79. eCollection 2014.
citation: Shanks AM, Avidan MS, Kheterpal S, Tremper KK, Vandervest JC, Cavanaugh JM, Mashour GA. Alerting thresholds for the prevention of intraoperative awareness with explicit recall: a secondary analysis of the Michigan Awareness Control Study. Eur J Anaesthesiol. 2015 May;32(5):346-53. doi: 10.1097/EJA.0000000000000123.
citation: Avidan MS, Palanca BJ, Glick D, Jacobsohn E, Villafranca A, O'Connor M, Mashour GA; BAG-RECALL Study Group. Protocol for the BAG-RECALL clinical trial: a prospective, multi-center, randomized, controlled trial to determine whether a bispectral index-guided protocol is superior to an anesthesia gas-guided protocol in reducing intraoperative awareness with explicit recall in high risk surgical patients. BMC Anesthesiol. 2009 Nov 30;9:8. doi: 10.1186/1471-2253-9-8.
citation: Mashour GA, Tremper KK, Avidan MS. Protocol for the "Michigan Awareness Control Study": A prospective, randomized, controlled trial comparing electronic alerts based on bispectral index monitoring or minimum alveolar concentration for the prevention of intraoperative awareness. BMC Anesthesiol. 2009 Nov 5;9:7. doi: 10.1186/1471-2253-9-7.