Adsorption of sevoflurane by soda-limes

Dry soda-lime adsorbs significant quantities of halothane, thus influencing on the speed of the induction of anaesthesia with the agent and also on the recovery from anesthesia. Sevoflurane is a new inhaled anesthetic. Although the chemical degradation of sevoflurane with soda-lime has been studied, no information is available about its adsorption by soda-lime. This issue can not be neglected clinically. Two different soda-limes were placed in saturated vapour of sevoflurane for 17 hours to weight adsorbed sevoflurane. Then soda-limes adsorbing sevoflurane was sealed in a test tube after air-drying for 1) 0 min, 2) 10 min, 3) 30 min and 4) 17 hours. The vapour phase of sevoflurane in the test tube at various temperatures were determined using gas chromatography. Sevoflurane vapour concentrations in the test tubes increased in a temperature-dependent manner. Those in the conventional soda-lime were higher than those in the new soda-lime under any experimental conditions. Sevoflurane was released from soda-limes even after air-drying for 17 hours. These results show that much amount of sevoflurane is adsorbed by soda-limes and is released easily in the air. Thus there is a possibility for our patients to inhale unexpected inhaled anesthetics, if we use our anesthetic machine repeatedly.