Abstract
Objective
Processed EEG monitoring during cardiopulmonary bypass (CPB) may help determine loss of consciousness and depth of anesthesia. This study compared the SNAP™ II and BIS Vista monitors in patients undergoing isoflurane anesthesia with normothermic CPB.
Methods
40 subjects undergoing CPB with isoflurane anesthesia were enrolled. Subjects were premedicated with 1–2 mg midazolam approximately 5 min prior to acquisition of baseline index values and anesthesia induced with midazolam and fentanyl. Anesthesia was maintained with isoflurane, midazolam, and fentanyl and a cis-atracurium infusion. SNAP™ II (version 1.2.9 algorithm 1.88) and BIS Vista (application version 3.00 platform version 2.03) indices were recorded at baseline, pre-induction, post-intubation, incision, start of CPB, every 15 min during CPB, end of CPB, and end of case. Agreement between methods was determined using Pearson correlation and the Bland–Altman method with repeated observa- tions.
Results
Twenty-four male and 12 female subjects completed the analysis. The correlation between SNAP™ II and BIS Vista index values was 0.61 (P < 0.005). A linear relationship between the difference in the indices and the average index values was observed following the induction of anesthesia. In awake subjects, the bias between the SNAP™ II and BIS Vista was 5 (95% CI 3–7). The limits of agreement were 23 (95% CI 19–26) and −13 (95% CI −9–−16). During anesthesia, the mean difference on a log scale was 0.11 (95% CI 0.09–0.12). The limits of agreement were 0.43 (95% CI 0.40–0.45) and −0.21 (95% CI −0.18–−0.24). The antilog of the mean difference demonstrated that the SNAP™ II value was 28% (95% CI 24–33%) higher than the BIS Vista value following induction of anesthesia.
Conclusions
The SNAP™ II monitor demonstrates a consistently positive bias during cardiopulmonary bypass under isoflurane anesthesia compared with the BIS Vista.
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Financial support for this study was provided by the Department of Anesthesiology, Northwestern University. Stryker Inc. supplied the SNAP™ II devices and disposables used in this study. This study was presented in part at the American Society of Anesthesiologist Annual Meeting Orlando Florida, October 20, 2008.
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Patel KM, Sherwani SS, Fitzgerald PC, McCarthy RJ. Comparison of SNAP™II and BIS Vista indices during normothermic cardiopulmonary bypass under isoflurane anesthesia.
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Patel, K.M., Sherwani, S.S., Fitzgerald, P.C. et al. Comparison of SNAP™ II and BIS Vista indices during normothermic cardiopulmonary bypass under isoflurane anesthesia. J Clin Monit Comput 25, 365–370 (2011). https://doi.org/10.1007/s10877-011-9313-1
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DOI: https://doi.org/10.1007/s10877-011-9313-1