EVALUATION OF 100% VERSUS 21% OXYGEN SUPPLEMENTATION IN COMMON SNAPPING TURTLES (CHELYDRA SERPENTINA) ANESTHETIZED WITH ALFAXALONE

In reptiles, respiration differs from that in mammals, with hypoxia rather than hypercapnia driving ventilation. Although veterinarians have anecdotally limited 100% oxygen supplementation in reptile anesthesia to mitigate respiratory depression and, theoretically, avoid prolonged anesthetic recovery, data to support this practice are lacking. The study objective is a comparison of supplementation with 100% versus 21% oxygen on anesthetic and cardiorespiratory parameters of 10 healthy, spontaneously ventilating common snapping turtles (Chelydra serpentina) anesthetized with alfaxalone. Using a randomized, complete crossover design with a 1-wk interval between treatments, turtles were administered alfaxalone (8 mg/kg IM), intubated, and supplemented with either 21% oxygen (room air) or 100% oxygen (1 L/min). Anesthetic timing (initial effect, intubation, extubation, recovery), venous blood gas data (baseline, 40 min, recovery) and serial physiologic variables (heart and respiratory rates, temperature, inhaled and exhaled gas concentrations, anesthetic depth) were compared between groups. Times to initial effect and intubation, and cumulative anesthetic depth scores were not significantly different between groups. In all turtles, sustained increase in heart rate and transient increase in respiratory rate were observed following alfaxalone administration and were not significantly different between groups. Respiratory rate for the remainder of the anesthesia was not significantly different between groups. Median (range) time to extubation (21%: 100 [90–126] min, 100%: 100 [69–116] min) and time to recovery (21%: 118 [100–130] min, 100%: 115 [85–130] min) were not significantly different between groups. Mean ± SD partial pressure of oxygen in venous blood was significantly higher with supplementation of 100% (104.5 ± 36.0 mm Hg) compared with 21% (35.8 ± 7.0 mm Hg) oxygen (P < 0.01). Supplementation with 100% oxygen did not decrease respiratory rate or delay anesthetic recovery time and resulted in significantly greater blood oxygen concentrations in alfaxalone-anesthetized juvenile snapping turtles, supporting the use of 100% oxygen supplementation during chelonian anesthesia.