Measuring the costs of inhaled anaesthetics

The cost of inhalation anaesthesia has received considerablestudy and is undoubtedly reduced by the use of low fresh gasflows. However, comparison between anaesthetics of the economiesachievable has only been made by computer modelling. We havecomputed anaesthetic usage for MAC-equivalent anaesthesia withisoflurane, desflurane, and sevoflurane in closed and open breathingsystems. We have compared these data with those derived duringclinical anaesthesia administered using a computer-controlledclosed system that measures anaesthetic usage and inspired concentrations.The inspired concentrations allow the usage that would haveoccurred in an open system to be calculated. Our computed predictionslie within the 95% confidence intervals of the measured data.Using prices current in our institution, sevoflurane and desfluranewould cost approximately twice as much as isoflurane in opensystems but only about 50% more than isoflurane in closed systems.Thus computer predictions have been validated by patient measurementsand the cost saving achieved by reducing the fresh gas flowis greater with less soluble anaesthetics. Br J Anaesth 2001; 87: 559–63