Abstract

Inhalant anesthesia is commonly used to restrain reptiles for a range of procedures, but rarely have comparisons between different gases been performed in rattlesnakes.^1,2 Prairie rattlesnakes (Crotalus viridis, n=12) were anesthetized using isoflurane, sevoflurane, or desflurane in a randomized cross-over study design to characterize the potency and physiologic effects of each anesthetic gas in the species. Parameters of anesthetic depth were recorded throughout induction and recovery, including loss and return of righting reflex, muscle tone, ability to intubate, response to tactile stimulation (monofilament), and return to spontaneous respiration. Physiologic data were recorded every 5 min throughout the anesthetic procedures, including heart rate, respiratory rate, and percent expired anesthetic gas. Snakes anesthetized with sevoflurane exhibited an anesthetic gas avoidance behavior during induction and had the longest recovery times to extubation (p=0.01601) and return of pressure response (p=0.04575). Snakes anesthetized with isoflurane had the longest righting reflex return (p=0.007488). There was no significant difference between anesthetic gas and loss of pressure response (p>0.05). Snakes anesthetized with desflurane had the quickest loss of righting reflex (p=0.02914) but did not achieve a deep surgical anesthetic plane as 4/12 snakes were unable to be intubated. Sevoflurane and isoflurane provided safe and effective anesthesia, whereas use of desflurane in rattlesnakes, and potentially other vipers, is not recommended.

Literature Cited

1.  Barter LS, Hawkins MG, Brosnan RJ, Antognini JF, Pypendop BH. Median effective dose of isoflurane, sevoflurane, and desflurane in green iguanas. Am J Vet Res. 2006;67:392–397.

2.  Maas A, Brunson DB. Comparison of anesthetic potency and cardiopulmonary effects of isoflurane and sevoflurane in colubrid snakes. In: Proceedings from the American Association of Zoo Veterinarians. 2002:306–308.