PARTLY EXHAUSTED SODA LIME OR SODA LIME WITH WATER ADDED, INHIBITS THE INCREASE IN COMPOUND-A CONCENTRATION IN THE CIRCLE SYSTEM DURING LOW-FLOW SEVOFLURANE ANESTHESIA

We performed low-flow sevoflurane anaesthesia at a flow rate of 1 litr e min(-1) in three groups (n = 8 each) using 600 g of fresh soda lime (control group), 600 g of soda lime with 60 ml of water added (water g roup) or 600 g of soda lime saturated with carbon dioxide, that is par tly exhausted soda lime (carbon dioxide group). Degradation products i n the system were measured hourly. Inspired and end-tidal carbon dioxi de and sevoflurane concentrations, carbon dioxide and temperature of t he soda lime were monitored. CF2 = C(CF3)-O-CH2F (compound A) was the only sevoflurane degradation product detected. The mean maximum concen tration of compound A was significantly higher in the control group (m ean 16.0 (SD 5.0) ppm) than in the water (1.4 (1.0) ppm) or carbon dio xide (4.0 (1.8) ppm) group, and the maximum temperature of the soda li me was significantly lower in the carbon dioxide group (30.7 (3.5)degr ees C) than in the control (43.4 (1.8)degrees C) or water (40.8 (1.8)d egrees C) group (P < 0.05). The use of partly exhausted soda lime or s oda lime with water added reduced compound A concentrations in the sys tem during low-flow sevoflurane anaesthesia.