Compound A production from sevoflurane is not less when KOH-free absorbentis used in a closed-circuit lung model system

In an in vitro study, less compound A was formed when a KOH-free carbon dio xide absorbent was used. To confirm this observation we used a lung model i n which carbon dioxide was fed in at 160 mi min(-1) and sampling gas was ta ken out for analysis at 200 mi min(-1); ventilation aimed for a PE'(CO2) Of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow por ts (T-in and T-out) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH -free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflur ane was injected using a syringe pump to obtain 2.1% E'. Compound A was mea sured by capillary gas chromatography combined with mass spectrometry. Medi an (range) compound A(insp) increased to a maximum of 22.7 (7.9) ppm for So dasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and i ncreased to <similar to>40 degreesC at 240 min. Contrary to expectation, co mpound A concentrations were greater with the KOH-free absorbent despite si milar canister temperatures with both absorbents.