title: Effect of total flow rate on the concentration of degradation products generated by reaction between sevoflurane and soda lime.
abstract: We have compared concentrations of degradation products in the circle system during sevoflurane anaesthesia at different fresh gas flows. Twenty-four patients underwent sevoflurane anaesthesia with fresh gas flows of 1 litre min-1 (1L group), 3 litre min-1 (3L group), or 6 litre min-1 (6L group) (n = 8 in each group). During anaesthesia, the concentrations of degradation products were measured every hour, and the temperature of soda lime, end-tidal carbon dioxide concentrations, inspired and end-tidal sevoflurane concentrations, and carbon dioxide elimination were measured. CF2 = C (CF3)-O-CH2F (compound A) was the only degradation product detected. The mean maximum concentration of compound A was 19.7 (SD 4.3) ppm in the 1L group, 8.1 (2.7) ppm in the 3L group and 2.1 (1.0) ppm in the 6L group (P < 0.05). The maximum temperature of soda lime was 44.6 (1.5) degrees C in the 1L group, 37.0 (4.4) degrees C in the 3L group and 29.1 (5.1) degrees C in the 6L group (P < 0.05). There were no significant differences in end-tidal sevoflurane concentration or mean carbon dioxide elimination between the groups. Only compound A was detected following anaesthesia, with higher concentrations observed at lower flow rates.
authors.affiliation: Department of Anaesthesiology and Intensive Care, Hamamatsu University School of Medicine, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Bito
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D000776:Anesthesiology / Q000379:methods*; D000777:Anesthetics; D017610:Calcium Compounds; D002245:Carbon Dioxide / Q000032:analysis; D004987:Ethers; D006801:Humans; D008738:Methyl Ethers; D008875:Middle Aged; D010087:Oxides; D012212:Rheology; D000077149:Sevoflurane; D012972:Sodium Hydroxide; D013696:Temperature; D013990:Tidal Volume; D014433:Tympanoplasty
chemical_list: D000777:Anesthetics; D017610:Calcium Compounds; D004987:Ethers; D008738:Methyl Ethers; D010087:Oxides; D002245:Carbon Dioxide; D000077149:Sevoflurane; C004569:soda lime; D012972:Sodium Hydroxide