Ventilation in reptiles is driven by blood O2 concentration rather than by CO2 concentration, wherein hypoxia serves as a stimulus for ventilation.1 Thus, high oxygen-tension environments may decrease spontaneous ventilation.1 Historically, it has been recommended that reptiles should recover from anesthesia while breathing room air rather than 100% O2 to encourage faster return to spontaneous breathing after inhalation anesthesia.2 However, there is limited scientific evidence to support this recommendation. In conscious reptiles, such as elephant trunk snakes (Acrochordus javanicus), savannah monitors (Varanus exanthematicus), and various chelonian species, exposure to 100% O2 results in a significantly reduced frequency of ventilation.3–7 However, more recent studies of Dumeril monitors (Varanus dumerili)8 and inland bearded dragons (Pogona vitticeps)9 anesthetized with inhalation anesthetics revealed that there were no significant or clinically relevant differences in physiologic variables, time to return of spontaneous ventilation, or recovery time when provided 21% O2 or 100% O2.
Sedation with injectable agents, rather than anesthesia with inhalation agents, may be more applicable in clinical settings for a variety of diagnostic and therapeutic procedures that do not require general anesthesia.10 A variety of protocols with injectable agents are used in reptiles, including protocols for dexmedetomidine-midazolam, dexmedetomidine-ketamine, and alfaxalone.10–12 However, the effect of Fio2 in sedated spontaneously breathing reptiles has not been clearly established. In Russian tortoises (Testudo horsfieldi) sedated with pentobarbital (50 mg/kg, SC), exposure to 100% O2 results in a transient reduction of ventilation frequency, a response that is abolished by transecting the vagal nerves.13 Therefore, the provision of supplemental O2 to sedated reptiles in a clinical setting may result in depression of respiration, which would be clinically undesirable because it could necessitate the need for endotracheal intubation and provision of intermittent positive-pressure ventilation in apneic animals.
The objective of the study reported here was to determine whether Fio2 has an effect on the quality of sedation, respiratory rate, and other cardiopulmonary variables of sedated, spontaneously breathing bearded dragons. We hypothesized that breathing a high concentration of O2 (100%) would decrease respiratory rates in sedated bearded dragons. In addition, reduced oxygenation secondary to inspiring room air (21% O2) would have an impact on recovery and postrecovery behavior, such as food intake.
Supported by Abaxis Global Diagnostics Inc.
Fraction of inspired oxygen
Oxygen saturation as measured by pulse oximetry
Total carbon dioxide
Research Randomizer, version 4.0, Geoffrey C. Urbaniak and Scott Plous, Middletown, Conn. Available at: www.randomizer.org. Accessed Oct 2, 2017.
digiDop, Digicare Animal Health, Boynton Beach, Fla.
Alfaxan, Jurox Pty Ltd, Rutherford, NSW, Australia.
Airgas USA LLC, Radnor, Pa.
Masimo Radical, Masimo Corp, Irvine, Calif.
Terumo Medical Corp, Elkton, Md.
CG4+ cartridge, Abaxis North America, Union City, Calif.
i-STAT, Abaxis North America, Union City, Calif.
N40 large mouse cage, Ancare Corp, Bellmore, NY.
SigmaPlot, version 13.0, Systat Software Inc, San Jose, Calif.
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