New parameters of skin conductance compared with Bispectral Index monitoring to assess emergence from total intravenous anaesthesia

Background: Arousal after total i.v. anaesthesia (TIVA) has been reportedto be detectable by monitoring the number of fluctuations persecond (NFSC), a parameter of skin conductance (SC). However,compared with monitoring of the bispectral index (BIS^®),the predictive probability of NFSC was significantly lower.The aim of this study was to determine the value of the twonew, not yet published parameters of SC, area under the curve(AUC) methods A and B, for monitoring emergence from TIVA comparedwith monitoring of NFSC and BIS^®. Methods: Twenty-five patients undergoing surgery were investigated. NFSC,AUC A, AUC B, BIS^®, and haemodynamic parameters (mean arterialpressure and heart rate) were recorded simultaneously. The performanceof the monitoring devices in distinguishing between the clinicalstates ‘steady-state anaesthesia’, ‘firstclinical reaction’, and ‘extubation’ werecompared using the method of prediction probability (Pk) calculation. Results: BIS^® showed the best performance in distinguishing between‘steady-state anaesthesia’ vs ‘first reaction’(Pk BIS^® 0.95; NFSC 0.73; AUC A 0.54; AUC B 0.62) and ‘steady-stateanaesthesia’ vs ‘extubation’ (Pk BIS^®0.99; NFSC 0.73; AUC A 0.71; AUC B 0.67). However, the timefrom first BIS^®>60/SC>0 to a first clinical reactionwas significantly shorter for BIS^® (median BIS^® 180s; NFSC 780 s; AUC A 750 s; AUC B 690 s; P < 0.001). Conclusions: AUC A and AUC B did not improve accuracy of SC monitoring inpatients waking after TIVA.