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Anesthesia & Analgesia:
doi: 10.1213/ANE.0b013e318281e9ad
Neuroscience in Anesthesiology and Perioperative Medicine: Brief Report

Assessment of Intraoperative Awareness with Explicit Recall: A Comparison of 2 Methods

Mashour, George A. MD, PhD*; Kent, Christopher MD; Picton, Paul MB, ChB, MRCP, FRCA*; Ramachandran, Satya Krishna MD, FRCA*; Tremper, Kevin K. PhD, MD*; Turner, Christopher R. MD, PhD, MBA; Shanks, Amy MS*; Avidan, Michael S. MBBCh§

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Author Information

From the *Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, Washington; Department of Anesthesiology, Bay Area Medical Center, Marintette, Wisconsin; and §Department of Anesthesiology, Washington University, St. Louis, Missouri.

Accepted for publication November 29, 2012.

The Michigan Awareness Control Study was generously funded by the Cerebral Function Monitoring grant (to G.A.M.) from the Foundation for Anesthesia Education and Research (Rochester, MN) and the American Society of Anesthesiologists (Park Ridge, IL); the National Institutes of Health (Bethesda, MD) (grant KL2 RR024987-01, to G.A.M.); and the Department of Anesthesiology, University of Michigan, Ann Arbor, MI.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to George Mashour, MD, PhD, Division of Neuroanesthesiology, Department of Anesthesiology, University of Michigan Medical School, 1H247 UH/SPC-5048, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5048. Address e-mail to gmashour@umich.edu.

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Abstract

BACKGROUND: Superiority of the modified Brice interview over quality assurance techniques in detecting intraoperative awareness with explicit recall has not been demonstrated definitively.

METHODS: We studied a single patient cohort to compare the detection of definite awareness using a single modified Brice interview (postoperative day 28–30) versus quality assurance data (postoperative day 1).

RESULTS: The incidence of awareness based on the modified Brice interview was 19 per 18,847 or 0.1%. Fewer awareness cases (incidence 0.02%) were detected by the quality assurance approach (P < 0.0001).

CONCLUSION: The modified Brice interview is the preferred modality for assessing intraoperative awareness with explicit recall.

Large prospective studies in Europe1 and the United States2 demonstrated that intraoperative awareness with explicit recall (AWR) occurs in approximately 1 to 2 cases per 1000. A large study of continuous quality improvement data brought these findings into question by demonstrating an incidence of approximately 1 per 14,560.3 It has been suggested that using quality assurance data is insufficient for the accurate capture of AWR events,4 but there has been no direct comparison of the modified Brice interview5,6 and quality assurance reports in the same study population. Since patients may be reluctant to tell their anesthesiologists about AWR,7 it will be important to answer this question to improve ongoing quality improvement initiatives in the field of anesthesiology.

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METHODS

We previously conducted a study of AWR comparing the Bispectral Index monitor to a protocol based on anesthetic concentrations (Michigan Awareness Control Study, clinical trial NCT00689091). Details of the study protocol8 and results of the trial9 have been published. The study received approval from the IRB of the University of Michigan, Ann Arbor, MI; the study was deemed to be of minimal risk, and written consent was waived. A full discussion of risks and benefits was conducted with each patient approached, and verbal consent was electronically documented in our perioperative information system (Centricity®, General Electric Healthcare, Waukesha, WI).

In the primary study, interviewers blinded to the study conditions conducted the modified Brice interview (Table 1) at a single point between postoperative day 28 and 30. On the basis of data obtained from the interviews, any patients responding “Yes” to question #3 specifically assessing recall had a second structured interview by an anesthesiologist, and the anesthesia record was reviewed. After all patients had the modified Brice and follow-up interviews, another committee of blinded reviewers assessed the results of the 2 interviews to determine whether the reported event was definite, possible, or no AWR.

Table 1
Table 1
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The comparison of the modified Brice interview and quality assurance screening for AWR was a prespecified secondary outcome of the parent trial.8 After recruitment and assessment of AWR events in the primary study were completed, we conducted an automated review of our quality assurance database for reports of “Intraoperative Awareness.” The objective of the current study was to assess how many AWR events detected with the modified Brice interview in the primary study were detected during the routine quality assurance follow-up that takes place on postoperative day 1. These interviews are conducted by nurses (for outpatients), anesthesiology residents (for inpatients), or certified registered nurse anesthetists (for inpatients). These interviewers were not investigators in the study and were distinct from the blinded observers conducting the Brice interview, the investigators who interviewed the patients answering yes to question #3 of the Brice interview, and the panel of experts determining the final designation of AWR events. Postoperative interviews typically consist of the open-ended question “Did you have any problems with the anesthesia for your surgery?” Any complaint of AWR is recorded in our anesthesia information management system by selecting “Intraoperative Awareness” from a picklist of postoperative complications.

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Statistics

The McNemar test was used to compare the 2 methods of assessing AWR, using a standard 2 × 2 classification table for positive and negative hits; a 2-tailed test was used to determine whether there was a significant difference in the proportion of AWR events. P < 0.05 was considered statistically significant. The McNemar test was performed using the MedCalc Software, Belgium. The asymptotic 95% confidence interval for the difference between proportions also was calculated.

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RESULTS

In the primary randomized controlled trial, there were 21,601 patients prospectively recruited; of this group, 18,836 patients completed the modified Brice interview at 28 to 30 days.8 The incidence of definite AWR in the entire study cohort was 19 per 18,836 or 0.1%. A review of quality assurance records for the same period revealed that 3 of the 19 patients reported AWR on routine postoperative interview, for an incidence of 3 per 18,836 or 0.02%. The incidence of AWR with the modified Brice interview was significantly higher than that detected by the routine postoperative interview (0.085% difference, 95% confidence interval 0.05%–0.14%, P < 0.0001; Table 2).

Table 2
Table 2
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DISCUSSION

In the current study, we demonstrate that the modified Brice interview is associated with superior detection of AWR compared with data derived from quality assurance measures. This suggests that the reduced incidence of AWR from quality assurance/improvement data in previous reports3,4 is likely due to methodological considerations rather than other factors. This finding is important in guiding future studies of AWR as well as patient care initiatives by data-sharing organizations such as the Anesthesia Quality Institute. Of note, the quality assurance approach in the study by Pollard et al.3 used a structured interview at several time points, which was distinct from the current study. The screening techniques were similar to the extent that neither specifically assessed for explicit recall.

An alternative hypothesis to explain our findings is that the increased incidence of AWR is associated with the later interview (postoperative day 28–30 vs postoperative day 1), rather than any interview technique or methodological consideration. In the study of Sandin et al.,1 35% of awareness events were identified at the 2-week postoperative interview; in Sebel et al.,2 approximately 50% of awareness events were identified in the interview at least 1 week postoperatively. Even assuming the higher percentage in the study of Sebel et al.,2 we would only anticipate a 2-fold difference between early and later interviews, rather than the 5-fold higher incidence (0.1% vs 0.02%) that was observed. We thus conclude that the increased incidence is not due to the timing of the interview, but rather predominantly due to the explicit assessment of AWR.

In conclusion, we demonstrate that the modified Brice interview is superior to quality assurance data in the detection of AWR. The results of this investigation are the strongest evidence to date that all studies or patient safety initiatives pertaining to AWR should be conducted with the modified Brice interview.

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DISCLOSURES

Name: George A. Mashour, MD, PhD.

Contribution: This author helped design the study, analyze data, and prepare the manuscript.

Attestation: George A. Mashour approved the final manuscript and reviewed the original study data. George A. Mashour is the archival author.

Name: Christopher Kent, MD.

Contribution: This author helped collect data and prepare the manuscript.

Attestation: Christopher Kent approved the final manuscript.

Name: Paul Picton, MB, ChB, MRCP, FRCA.

Contribution: This author helped collect data and prepare the manuscript.

Attestation: Paul Picton approved the final manuscript.

Name: Satya Krishna Ramachandran, MD, FRCA.

Contribution: This author helped collect data and prepare the manuscript.

Attestation: Satya Krishna Ramachandran approved the final manuscript.

Name: Kevin K. Tremper, PhD, MD.

Contribution: This author helped collect data and prepare the manuscript.

Attestation: Kevin K. Tremper approved the final manuscript.

Name: Christopher R. Turner, MD, PhD, MBA.

Contribution: This author helped collect data and prepare the manuscript.

Attestation: Christopher R. Turner approved the final manuscript.

Name: Amy Shanks, MS.

Contribution: This author helped analyze the data and prepare the manuscript.

Attestation: Amy Shanks approved the final manuscript.

Name: Michael S. Avidan, MBBCh.

Contribution: This author helped design the study, analyze the data, and prepare the manuscript.

Attestation: Michael S. Avidan approved the final study and reviewed the original study data.

This manuscript was handled by: Gregory J. Crosby, MD.

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REFERENCES

1. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet. 2000;355:707–11

2. Sebel PS, Bowdle TA, Ghoneim MM, Rampil IJ, Padilla RE, Gan TJ, Domino KB. The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg. 2004;99:833–9

3. Pollard RJ, Coyle JP, Gilbert RL, Beck JE. Intraoperative awareness in a regional medical system: a review of 3 years’ data. Anesthesiology. 2007;106:269–74

4. Mashour GA, Wang LY, Turner CR, Vandervest JC, Shanks A, Tremper KK. A retrospective study of intraoperative awareness with methodological implications. Anesth Analg. 2009;108:521–6

5. Brice DD, Hetherington RR, Utting JE. A simple study of awareness and dreaming during anaesthesia. Br J Anaesth. 1970;42:535–42

6. Abouleish E, Taylor FH. Effect of morphine-diazepam on signs of anesthesia, awareness, and dreams of patients under N2O for cesarean section. Anesth Analg. 1976;55:702–5

7. Moerman N, Bonke B, Oosting J. Awareness and recall during general anesthesia. Facts and feelings. Anesthesiology. 1993;79:454–64

8. 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;9:7

9. Mashour GA, Shanks A, Tremper KK, Kheterpal S, Turner CR, Ramachandran SK, Picton P, Schueller C, Morris M, Vandervest JC, Lin N, Avidan MS. Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial. Anesthesiology. 2012;117:717–25

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