Quantitative electroencephalographic analysis as a tool for predicting the depth of sedation of sedation induced by propofol, midazolam and ketamine / 中华麻醉学杂志

ABSTRACT

Objective To evaluated the acccuracy of the two quantitative electroencephalographic parameters-bispectral index (BIS) and 95% specrral edge frequency (95% SEF) for measuring the depth of sedation induced by propofol, midazolam and ketamine. Methods Forty-five ASA Ⅰ - Ⅱ patients aged 30-59 yr weighing 46-80 kg scheduled for elective general thoracic or abdominal surgery were randomized to receive an infusion of propofol at a rate of 8 mg?kg-1?h-1 (group P , n = 15) or midazolam at 0.5 mg?kg-1?h-1 (group M, n = 15) or ketamine at 4 mg?kg-1? h-1 (group K, n = 15) . The patients were unpremedicated. The depth of sedation was assessed using OAAS scale (5 = wide awake , 1 = no response to prodding or shaking ) at 3 min intervals. BIS and 95 % SEF were continuously monitored. The BIS and 95% SEF values at each OAAS score (5-1) were recorded. The relations between BIS, 95 % SEF and sedation scores were determined in each group. The ED50 values of BIS and 95% SEF50 for loss of consciousness and their 95% confidence internals were calculated. Prediction probability(Pk) values for BIS and 95% SEF were compared among the drugs. Results There were no significant differences among the 3 groups with respect to age, body weight, sex and duration of drug infusion. With increasing sedation there was a progressive decrease in BIS and 95 % SEF values in group P and M but no significant changes in BIS and 95 % SEF values were seen in group K. The BIS and 95 % SEF positively correlated with OAAS score in group P and M but not in group K. The BIS50 was 65.9 in group P and 70.7 in group M,but inestimable in group K.The 95% SEF50 was 20.4 in group P and inestimable in group M and K. The Pk values for BIS and 95 % SEF were higher in P group than in M group and were not significantly different from 0.5 indicating a very poor predictive performance . Conclusion The accuracy of BIS and 95 % SEF for assessing the depth of sedation is greater with propofol. BIS is more sensitive than 95% SEF for the same anesthesia.