Skin conductance monitoring compared with bispectral index® monitoring to assess emergence from general anaesthesia using sevoflurane and remifentanil

Background. Changes in skin conductance have previously been reported to correlate well with plasma levels of stress hormones and awakening stimuli. In this study, monitoring of skin conductance during emergence from general anaesthesia was compared with the monitoring of bispectral index (BIS). Methods. Twenty-five patients undergoing minor elective surgery were investigated. The number of fluctuations in mean skin conductance (NFSC), BIS and haemodynamic parameters were recorded simultaneously. The performance of the monitoring devices to predict and distinguish between the clinical states 'steady-state anaesthesia', 'first reaction' and 'extubation' were compared using the method of prediction probability (P-K) calculation. Results. Both monitors showed similar performance in distinguishing between 'steady-state anaesthesia' vs 'first reaction' (P-K NFSC 0.89; BIS (R) 0.94) and 'steady-state anaesthesia' vs 'extubation' (P-K NFSC 0.96; BIS (R) 0.96). The response times of the monitors, to indicate the likelihood of 'first reaction', were not significantly different. Conclusions. NFSC, as a parameter of skin conductance, performed similarly to BIS in patients waking after a general anaesthetic.