Minimum alveolar concentration (MAC) of xenon in intubated swine.

Abstract

The minimum alveolar concentration (MAC) is a traditional index of the hypnotic potency of an inhalational anaesthetic. To investigate the anaesthetic as well as the unwanted effects of xenon (Xe) in a swine model, it is useful to know MAC(Xe). The study was performed using ten swine (weight 27.8-35.4 kg) anaesthetized with halothane and Xe 0, 15, 30, 40, 50 and 65% in oxygen. With each Xe concentration, various concentrations of halothane were administered in a step-by-step design. For each combination, a supramaximal pain stimulus (claw clamp) was applied and the appearance of a withdrawal reaction was recorded. The MAC(Xe) with halothane was calculated using a logistic regression model. During stable ventilation, haemodynamics and temperature, MAC(Xe) value was determined as 119 vol. % (95% confidence limits 103-135). MAC(Xe) in swine was calculated by extrapolation of a logistic regression model. Its theoretical value is 119 vol. %.