Clinical study of relationships between spectral entropy and movement at skin incision during propofol anaesthesia

Objective:To study if the spectral entropy can predict movement at skin incision during propofol anaesthesia and compare it with BIS.Methods:Twenty ASA II patients undergoing elective abdominal surgery were studied.They were allocated into two groups of mover and non-mover according to whether they had response to skin incision or not.Anaesthesia was induced with propofol,succinylcholine and fentanyl and then was maintained with propofol at 20 mg·kg^-1·h^-1 infusion rate.Operation began 15min later.The propofol infusion rate was decreased by 10 percent for the next patient if movement was not detected or increased by 10 percent if movement was detected.Each case was simutaneously monitered with spectral entropy and BIS.Data was recorded at following time: baseline values,60 and 30s before skin incision,45 and 120s after skin incision.Results:Entropy index had significant differences between two groups（P＜0.05）,but BIS index hadn't（P＞0.05）;Entropy index could predict movement with P_k of 0.8935 and 0.8872 respectively but BIS couldn't with P_k of 0.5719;logistic regressive equations of prediction probability and entropy index were ln P_k/（1-P_k）=26.505-0.394x and ln P_k/（1-P_k）=28.553-0.435x respectively.Conclusion:Entropy index can predict movement during propofol anaesthesia,which can reflect analgesic depth of anesthesia.