Accurate monitoring of oxygenation in reptiles, especially snakes, is challenging for multiple reasons, but vital for assessment of physiologic state, especially during anesthesia. Traditional pulse oximetry (SpO2) is limited by the unique anatomy and physiology of reptiles, and monitoring trends is generally considered the most clinically relevant use.2 Transcutaneous oxygen monitoring utilizes near-infrared spectroscopy to assess a mixture of arterial, venous, and capillary flow to measure regional oxygen saturation (rSO2).4 Uses in human medicine include assessment of cerebral oxygenation during anesthesia and assessment of soft tissues, specifically during wound healing.1,3 In the present study, nine Louisiana pine snakes (Pituophis ruthveni) were monitored through four phases of an anesthetic event: breathing room air, supplied with supplemental oxygen, during sedation, and recovery. rSO2, measured over both the liver (rSO2Liver) and at the midpoint of the body (rSO2Half), and SpO2, were compared to the venous partial pressure of oxygen (PvO2) at the end of each phase. Strong positive associations were found between PvO2 and both rSO2Liver (r=0.72) and rSO2Half (r=0.63) irrespective of phase, but not with SpO2 (r=0.3). Strength of correlation varied with each phase but was universally strongest for rSO2Liver. Strengths of associations were further increased when rSO2Liver values of <60% were excluded from analyses. The use of rSO2 in snakes appears to have merit in assessing oxygenation levels of snakes, particularly when compared to traditional pulse oximetry.
The authors would like to thank the herpetology staff of Zoo Knoxville, in particular Michael Ogle. In addition, statistical assistance from Joshua Price was appreciated, and Mitch Sandifer at Masimo corporation for the use of the equipment.
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