Bispectral index monitors, non-invasive cardiac output monitors, and haemodynamics of induction agents

摘要

Editor-We read with great interest the recent article by Petrun and Kamenik regarding the use of a bispectral index (BIS) monitor as a guide to induce anaesthesia using an infusion technique with propofol compared with etomidate. This infusion technique is a plausible concept because of the BIS monitoring. Infusion techniques using propofol were performed many years ago, dating back to 1983-7 when BIS monitors were not in clinical use. Minimally invasive monitors to measure cardiovascular haemodynamic variables, such as the Lidco rapid monitor (Lidco cardiac sensor system; Cambridge, UK) were also not in clinical use. According to the authors, the monitor provides beat-to-beat measurements of cardiac index (Cl) by analysing the arterial pressure (AP) tracing. The displayed values are nominal and are derived from a population-based nomogram which may not be absolutely accurate. Therefore, the numbers recorded may be even more negative than expressed in the article.