Lack of degradation of sevoflurane by a new carbon dioxide absorbent in humans

Abstract

Background: Potent inhaled anesthetics degrade in the presence of the strong bases (sodium hydroxide or potassium hydroxide) in carbon dioxide (CO2) absorbents. A new absorbent, Amsorb (Armstrong Medical Ltd., Coleraine, Northern Ireland), does not employ these strong bases. This study compared the scavenging efficacy and compound A production of two commercially available absorbents (soda lime and barium hydroxide lime) with Amsorb in humans undergoing general anesthesia. Methods: Four healthy volunteers were anesthetized on different days with desflurane, sevoflurane, enflurane, and isoflurane. End-tidal carbon dioxide (ETco2) and anesthetic concentrations were measured with infrared spectroscopy; blood pressure and arterial blood gases were obtained from a radial artery catheter. Each anesthetic exposure lasted 3 h, during which the three fresh (normally hydrated) CO2 absorbents were used for a period of 1 h each. Anesthesia was administered with a fresh gas flow rate of 21/min of air:oxygen (50:50). Tidal volume was 10 ml/kg; respiratory rate was 8 breaths/min. Arterial blood gases were obtained at baseline and after each hour. Inspired concentrations of compound A were measured after 15, 30, and 60 min of anesthetic administration for each CO2 absorbent. Results: Arterial blood gases and ETco2 were not different among three CO2 absorbents. During sevoflurane, compound A formed with barium hydroxide lime and soda lime, but not with Amsorb. Conclusions: This new CO2 absorbent effectively scavenged CO2 and was not associated with compound A production.