Electrocardiographic electrodes provide the same results as expensive special sensors in the routine monitoring of anesthetic depth.

Abstract

The Bispectral Index (BIS) is a mathematically derived electroencephalographic (EEG) derivative that has been introduced to monitor depth of anesthesia (1,2). The A-2000 BIS monitoring system (Aspect Medical Systems, Inc., Newton, MA) is currently the only commercially available system to monitor depth of anesthesia. In several studies, its propensity to optimize the use of hypnotics to maintain and achieve a certain depth of anesthesia has been described (3,4). Some studies have even proposed that the routine use of the monitoring system can decrease awareness (1,5), an increasing factor in malpractice claims. The cost-benefit calculations for BIS monitoring suffer from the fact that like its predecessor, the 1000-A BIS monitor, the A-2000 BIS monitoring system demands the use of expensive, special electrodes (6). Although the application of the single-use BIS sensor is very comfortable and easy to use, its high price of approximately $10-20 US prevents many anesthesiologists from using it. Furthermore, whereas the former model of the monitor (1000-A BIS monitor; Aspect Medical Systems, Inc.) used standardized connectors, which allowed the use of other electrodes such as electrocardiogram (ECG), the new monitoring system makes this very difficult because of special connectors that match the equivalent connector at the proximal BIS sensor site. The purpose of this prospective study was to compare BIS values derived from the original BIS sensor with BIS values derived from commercially available ECG electrodes. This comparison was made possible by designing and manufacturing a connector allowing the use of ECG electrodes. The Bispectral Index (BIS) monitor adequately monitors depth of anesthesia. The routine use of this monitor has been hampered by the benefit-cost equation because only special expensive electrodes can be used. We examined the agreement of BIS values obtained by original sensor electrodes and commercial electrocardiogram (ECG) electrodes. These ECG electrodes can replace more expensive BIS sensors.