Which anaesthetic agent for maintenance during normothermic cardiopulmonary bypass?
R. R. D. Marks1 1 The Northern General Hospital, Herries Road, Sheffield S5 7AU, UK E-mail: richardmarks@doctors.org.uk The choice of agent for anaesthetic maintenance during cardiopulmonary bypass has developed in an arbitrary manner. As a result, strong personal preferences for i.v. or volatile agent anaesthesia are frequently expressed, with a dearth of carefully considered evidence to support either argument. The process of cardiopulmonary bypass itself has complex effects on the pharmacokinetics of i.v. anaesthetic agents, because of haemodilution and altered visceral perfusion.1 The relatively advanced age of the patient population undergoing heart surgery may also increase the variability of effect of i.v. anaesthetics. The coexistence of systemic atheroma further reduces visceral perfusion and may affect the clearance of these drugs. Extracorporeal circulation effectively substitutes for the patient s own heart and lungs, and during bypass, gas exchange is achieved via an artif
