Anesthesia of reptiles (Proceedings)

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Anesthesia of reptiles (Proceedings)

May 01, 2011

General principles

Reptiles are very resilient and capable of surviving physiological changes e.g. severe hypoxemia, that would rapidly kill a mammal.

Hypothermia should not be used as a method of restraint. It will induce immobility but will not provide analgesia. Hypothermia will also impair drug metabolism, digestion and immune function.

For short non-painful procedures such as radiography, the vagal-vagal response can be used. Pressure over the eyes of most large lizards and crocodilians for about a minute will cause a decrease in heart rate and blood pressure and the reptile may become inactive enough for minor non-stimulating procedures.

In reptiles, administration of safe and effective anesthesia and analgesia presents unique challenges to the veterinary practitioner. Compared with mammalian and avian species, reptile anatomy and physiology differs considerably and knowledge of normal anatomy and physiology of the species to be anesthetized is essential. In particular, reptile respiratory anatomy and function is different from mammalian and avian species and affects response to anesthetic agents. In addition, the pathophysiology of many reptilian diseases is different from similar conditions described in mammals. The design of anesthetic and analgesic protocols in reptile patients is further complicated by species and individual differences in response to commonly used anesthetic and analgesic agents. Knowledge and understanding of reptilian anesthesia and analgesia has increased of the past decade, however relatively few studies have investigated the cardiopulmonary responses of reptiles to various anesthetic agents. Assessment of cardiopulmonary performance in reptiles is complicated by the fact that anesthesia monitoring devices (eg, pulse oximetry) commonly used in domestic animals are often of limited value in reptiles and have not been validated for use in reptilian species. Investigations into effective reptile analgesia have become more numerous and have shown species differences in response to analgesic agents and protocols. Effective management of preoperative, intraoperative, and postoperative pain in reptiles is important to eliminate the negative impact of pain on many body functions including the immune system and cardiopulmonary system.

Preanesthetic evaluation

A detailed history of the patient should be obtained including environmental conditions as well as husbandry practices. Many disease problems diagnosed in reptiles are directly associated with inadequate husbandry such as improper nutrition and failure to provide the animal with appropriate temperature and humidity conditions. A complete visual and physical evaluation of the patient is essential. Abnormalities should be recorded while particular attention should be paid to the cardiopulmonary system. Rate and depth of respiration should be evaluated for signs of respiratory tract disease. Baseline heart and respiratory rates should be recorded. Often, reptiles are presented with chronic disease processes and physical and laboratory findings indicating dehydration, malnutrition and presence of secondary bacterial infections are common. If possible, a venous blood sample should be collected for determination of hematological and plasma biochemical parameters. Minimally, a blood sample should be collected for determination of blood glucose, total protein and packed cell volume. Based on physical examination and laboratory findings, abnormalities and deficiencies should be treated prior to anesthesia. The patient should be placed in a temperature and humidity controlled environment. Small animal incubators are ideal for this purpose and supportive measures including fluid therapy, nutritional support and antimicrobial therapy should be instituted. The patient should also be evaluated for any signs of pain and discomfort and if indicated, analgesic therapy should be initiated. For elective surgical procedures were postoperative pain is anticipated, administration of pre-emptive analgesia is most effective for the management of intraoperative and postoperative pain.