Determination of Continuous Atracurium Infusion Rate in Dogs Undergoing Whole-Body Hyperthermia¹

Infusion rates for atracurium were calculated from multiple bolus injection data for normothermic (38°C; n = 4) and hyperthermic (42°C; n = 14) dogs anesthetized with thiopental and oxymorphone while undergoing whole-body hyperthermia treatment. The calculated infusion rate for atracurium at 38°C was 6.2 ± 0.3 µg/kg/min and the calculated infusion rate at 42°C was 8.5 ± 0.4 µg/kg/min. Infusion of atracurium at the calculated infusion rate of 8.5 µg/kg/min produced an estimated 90–100% neuromuscular blockade during heating from 38–42°C and at 42°C. Following discontinuation of the infusion and cooling to 38°C, neuromuscular function returned to normal within 20 min with no evidence of recurarization. Atracurium infusion rates appear to be linear and related to body temperature from 26–42°C. Clinically useful neuromuscular blockade in dogs may be obtained during whole-body hyperthermia by utilizing the 42°C atracurium infusion rate throughout the 38–42°C heating phase.