Measuring the costs of inhaled anaesthetics

The cost of inhalation anaesthesia has received considerable study and is u ndoubtedly reduced by the use of low fresh gas flows. However, comparison b etween anaesthetics of the economies achievable has only been made by compu ter modelling. We have computed anaesthetic usage for MAC-equivalent anaest hesia with isoflurane, desflurane, and sevoflurane in closed and open breat hing systems. We have compared these data with those derived during clinica l anaesthesia administered using a computer-controlled closed system that m easures anaesthetic usage and inspired concentrations. The inspired concent rations allow the usage that would have occurred in an open system to be ca lculated. Our computed predictions lie within the 95% confidence intervals of the measured data. Using prices current in our institution, sevoflurane and desflurane would cost approximately twice as much as isoflurane in open systems but only about 50% more than isoflurane in closed systems. Thus co mputer predictions have been validated by patient measurements and the cost saving achieved by reducing the fresh gas flow is greater with less solubl e anaesthetics.