Abstract

In reptiles, respiration differs from mammals, with hypoxia rather than hypercapnia driving ventilation.¹ Therefore, veterinarians have anecdotally limited 100% oxygen supplementation in reptile anesthesia to mitigate respiratory depression and avoid prolonged anesthetic recovery. However, recent studies in lizards challenge this practice, demonstrating 100% oxygen supplementation did not induce hypoventilation, anesthetic recovery time was not significantly different, and rather was beneficial in maintaining higher blood oxygenation compared to room air.^2,3 While these studies in terrestrial lizards are powerful evidence for informing anesthesia optimization, application to other reptile species, such as aquatic chelonians, may be inappropriate due to the differences in respiratory physiology. The objective of the study is a comparison of 100% oxygen versus 21% oxygen supplementation on anesthetic parameters of aquatic turtles anesthetized with alfaxalone. In a randomized, crossover study with a two-week washout period, ten clinically healthy, juvenile common snapping turtles (Chelydra serpentina) were administered intravenous alfaxalone 5 mg/kg, intubated, and allowed to spontaneously ventilate 100% oxygen (fraction of inspired oxygen [FiO₂] 1.0, 1 L/min) or room air (FiO₂ 0.21) until extubation. Collected data included induction and recovery times, and serial physiologic parameters including heart rate and rhythm, respiratory rate, cloacal temperature, end-tidal CO₂, and anesthetic depth. Serial venous blood gas analysis (baseline, 30 and 60 minutes) was performed. Collected data were compared between groups. Preliminary data demonstrated no change from baseline in respiratory rate with 100% oxygen supplementation. This research serves to optimize anesthesia of aquatic turtles and may support conservation efforts in at-risk species, including sea turtles.

Acknowledgments

The authors wish to thank the Mystic Aquarium husbandry team for their efforts caring for the turtles and support in data collection. Research was conducted under the Connecticut Department of Energy and Environmental Protection permit and approved by the Mystic Aquarium Institutional Animal Care and Use Committee.

*Presenting author

Literature Cited

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2.  Ratliff C, Parkinson L, Christoph M. Effects of the fraction of inspired oxygen on alfaxalone-sedated inland bearded dragons (Pogona vitticeps). Am J Vet Res. 2019;80:129–134.

3.  Odette O, Churgin S, Sladky K, Lesley S. Anesthetic induction and recovery parameters in bearded dragons (Pogona vitticeps): comparison of isoflurane delivered in 100% oxygen versus 21% oxygen. J Zoo Wildl Med. 2015;46:534–539.