Bispectral index monitoring: comparison of two types of electrode

Bis-monitoring is a new method of monitoring anaesthetic depth. Bis-monitoring is easy to perform, but the Bis-monitor and the original, disposable electrodes are expensive. The aim of this study was to determine whether the original Zipprep electrodes could be replaced by the much cheaper electrocardiogram electrodes. We compared bispectral index measurements, conducted using both types of electrode in the same patients before anaesthesia, and during light and deep anaesthesia, in patients randomly allocated to receive either sevoflurane or propofol anaesthesia. We found very good agreement between the measurements from the two different sets of electrodes. The impedance in the electrocardiogram electrodes was higher than in the Zipprep electrodes, but this did not affect the bispectral index. No other problems with either type of electrode were detected. It is concluded that Zipprep electrodes can be replaced by electrocardiogram electrodes in normal clinical practice.