title: Sevoflurane degradation by soda lime in a circle breathing system.
abstract: Sevoflurane is degraded by soda lime to a vinyl ether commonly referred to as compound A. We measured the concentration of compound A in the circle breathing system of 31 patients receiving sevoflurane anaesthesia. Inspiratory and expiratory gas samples were analysed using gas chromatography and flame ionisation detection. The end-tidal sevoflurane concentration and soda lime temperature were recorded. The peak compound A concentration ranged between 10 to 32 ppm in the inspiratory limb and 7 to 26 ppm in the expiratory limb. There was a positive correlation between the peak compound A concentration and the end-tidal sevoflurane concentration (r2 = 0.545, p < 0.0001) and the soda lime temperature (r2 = 0.301, p = 0.0014). We conclude that the end-tidal concentration of sevoflurane and the temperature of the soda lime are important variables in determining concentration of compound A in a circle system.
authors: Academic Department of Anaesthetics, St Mary's Hospital Medical School, Imperial College of Science, London.
authors: I T
authors: IT
authors: Munday
authors: P M
authors: PM
authors: Ward
authors: N D
authors: ND
authors: Foden
authors: R M
authors: RM
authors: Jones
authors: F N
authors: FN
authors: Van Pelt
authors: J G
authors: JG
authors: Kenna
mesh_terms: D000328:Adult; D000764:Anesthesia, Closed-Circuit; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000737:chemistry*; D017610:Calcium Compounds; D004334:Drug Administration Schedule; D004987:Ethers / Q000008:administration & dosage / Q000737:chemistry*; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry; D008738:Methyl Ethers; D010087:Oxides; D000077149:Sevoflurane; D012972:Sodium Hydroxide; D013696:Temperature
chemical_list: D018685:Anesthetics, Inhalation; D017610:Calcium Compounds; D004987:Ethers; D006845:Hydrocarbons, Fluorinated; D008738:Methyl Ethers; D010087:Oxides; D000077149:Sevoflurane; C004569:soda lime; D012972:Sodium Hydroxide; C078742:fluoromethyl 2,2-difluoro-1-(trifluoromethyl)vinyl ether