Monitoring of Depth of Anesthesia using Entropy Monitor during Cardiopulmonary Bypass

Abstract

Aim:To monitor the depth of anesthesia using entropy monitor during cardiopulmonary bypass (CPB) using (1) numerical indices provided by entropy monitor [response entropy (RE) and state entropy (SE), burst suppression ratio (BSR)] and (2) modified version of Brice questionnaire used after 48 hours of surgery. Materials and methods:Design: Prospective observational study. Setting: Cardiovascular thoracic surgery (CVTS) operation theater (OT) of our hospital. Participants: 100 patients undergoing CPB surgery and willing to participate in the study. Intervention: Brain and facial muscular activity recorded using disposable sensor with three electrodes attached to patient's forehead and a sensor cable that connects the sensor to entropy module. Entropy indices were calculated and displayed in real time. All patients were then interviewed 48 hours after surgery about any recall of intraoperative awareness using the modified Brice questionnaire. Measurements and results:Basic statistics was assessed by using MS Excel Office 2007 data analysis Tool Pack. The association between two variables was determined by Pearson chi-square test. After skin incision, mean RT and ST were found to decrease significantly till peak hypothermia. After start of rewarming, mean RT and ST were found to increase significantly till skin closure. Conclusion:In our study, we did not find any awareness in all 100 studied subjects, leading to the conclusion that anesthesia technique used for CPB is optimal.Clinical significance: It can be concluded that entropy monitor might aid CPB surgery in many ways. It monitors the depth of anesthesia and probably prevents intraoperative awareness, helps in reducing anesthetic dosage, and hence, reduction in cost of anesthesia.