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Abstract

The anatomy and physiology of reptiles and mammals are in many ways different, and will therefore possibly complicate anesthetic administration. Lizards are ectothermic and one should keep in mind that a decrease in the lizard’s environmental temperature may result in reductions in anesthetic metabolism. Respiratory depression is a profound problem because lizards lack a diaphragm, making inhalation and expiration completely active processes. This, in combination with cardiac shunting and breath holding makes the effects of anesthesia unpredictable. Since lizards have a renal-portal-system, anesthetics injected in the caudal half of the body may be eliminated at a different speed than if injected elsewhere.
Premedication may be used to facilitate handling, injection and to reduce stress and high usage of anesthetics.
Inhalant anesthetics are safe to use and provides easily controlled depth and duration. Isoflurane is commonly used and has a rapid induction and recovery period but may cause decreased blood pressure and suppress spontaneous ventilation. Sevoflurane gives an even faster induction than isoflurane. Inhalant anesthetics in general have short duration, does not give adequate analgesia or depth, and require constant maintenance.
Injectable anesthetics often have long duration and thus give longer recovery in comparison to inhalant anesthetics. Most commonly used are ketamine, propofol and tiletamine together with zolazepam. Ketamine in lower doses are tranquillizing, while higher doses achieve surgical anesthesia. However it provides no analgesia, depth of anesthesia is difficult to evaluate and high doses often cause prolonged recovery. Tiletamine and zolazepam together gives anesthesia, analgesia and muscle relaxation. The duration is longer than with ketamine and entail longer recovery, nevertheless tiletamine with zolazepam is recommended when treating larger animals since smaller volumes are required in comparison to ketamine. Propofol can be used to provide induction or maintenance of anesthesia. Recovery is fast and organ toxicity is minimal.