A Comparison of Bispectral Index between Spinal and Epidural Anesthesia during Cesarean Section

Background: Many studies have shown spinal anesthesia with sedative drugs to affect bispectral index (BIS). On the other hand, spinal anesthesia, even without sedative drugs, reduces the level of consciousness. It has also been suggested that BIS value decreases in cases of epidural anesthesia. The aim of this study was to compare the effects of spinal and epidural anesthesia on BIS during cesarean section. Methods : In a double-blind randomized controlled clinical trial study, a group of pregnant women with American Society of Anesthesiologists (ASA) class I or II who were elective cesarean candidates in Beheshti Hospital (Isfahan, Iran) were evaluated. The patients were divided into two groups to receive either spinal or epidural anesthesia. BIS, heart rate (HR), mean arterial pressure (MAP), signal quality index (SQI), electromyography (EMG), consciousness block level, and central temperature (tympanic) were measured in all subjects. The values were registered immediately after anesthesia and at the 5th, 10th, 15th, 30th, 45th, 60th, 90th, and 120th minutes after spinal and epidural anesthesia. The mean changes were compared and analyzed in SPSS. Results: From the recruited subjects, 65 individuals completed the study in each group and their data was analyzed. There were no significant differences between the two groups in terms of mean age, height, weight, body mass index, MAP, SQI, percent of EMG, central temperature, or recorded BIS values at any point of time. Conclusion: According to our results, BIS values during surgery start to decrease immediately after the injection of the spinal or epidural anesthesia drugs. The greatest reduction compared to baseline BIS values occurred at 30th, 45th, and 60th minutes after induction of anesthesia. However, spinal or epidural anesthesia did not have different effects on BIS values during cesarean section. Key words: Anesthesia, Bispectral index, Epidural, Spinal