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doi: 10.1097/ALN.0b013e318289b948

To BIS or Not to BIS

Helwani, Mohammad A. M.D.

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To the Editor:
I read with interest the study by Mashour et al.1 The authors are to be congratulated for having performed this large randomized trial to answer an important question regarding the utility of bispectral index monitor and comparing that to minimum alveolar concentration level alarm system.
There are few points that warrant clarification. First, the author included patients who received total intravenous anesthesia. However, the details of this subgroup of patients were not provided. The method of determining the minimum alveolar concentration level in the no bispectral index total intravenous anesthesia patients, the alarm limits, and the incidence of awareness in these patients were not described.
Second, the inter-rater agreement using Fleiss κ statistic for the three blinded assessments of awareness showed fair agreement (0.25). Can the authors comment on the low level of agreement and provide the confidence interval for κ?
Third, 36% of patients did not have bispectral index data recorded because of technical issues. While this could provide a third arm for comparison, it may also create some bias. Providers who did not receive an alarm might have decreased vigilance as they could have depended on the alarm system. Adding a third arm of routine care in the design might have provided valuable information.
Finally, it would have been interesting to learn more about the 19 definite awareness cases in this large sample which could help in refining the characteristics of high-risk patients.
Mohammad A. Helwani M.D.
, Washington University School of Medicine at Saint Louis, St. Louis, Missouri.
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1. 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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