VN April 2023

Vetnews | April 2023 9 Correction of hypothermia is challenging and every effort should be made to maintain normothermia or minimize hypothermia in the exotic animal patient (Table 3). 10,22 EXOTIC COMPANION MAMMALS Body temperature can quickly plummet below 35ºC (95ºF) when small mammals are not provided with supplemental heat. 23,27 Flecknell (2015) has described reductions in body temperature up to 10ºC in anesthetized mice in as little as 15-20 minutes. Since tiny patients can sometimes heat up just as quickly as they cool down, it is also important to carefully monitor temperature during recovery to prevent hyperthermia and/or burns. 17 Marsupials normally have a lower body temperature than eutherian mammals (Table 1). To effectively measure temperature, insert the thermometer into the dorsal part of the cloaca, which communicates with the rectum. 15 BIRDS Birds, particularly smaller species, have higher metabolic rates and higher body temperatures when compared to mammals of similar size. Normal body temperature ranges between 39-42ºC (102.2-107.6ºF) in many avian species. 4,6,17,18,22,32 This high body temperature creates a steep temperature gradient between the bird’s core temperature and the temperature of the environment, which can to lead to rapid and dramatic heat loss when a bird is placed under general anesthesia. 6,17 The superior insulation provided by plumage in waterfowl and other aquatic birds can cause significant hyperthermia, particularly if the bird struggles during induction or must be captured under field conditions. 12,22 Additionally, some aquatic birds can shunt blood from their periphery to preserve core body temperature, making cloacal temperatures inaccurate. 12 REPTILES Reptiles are poikilotherms. General metabolism and cardiovascular physiology, which affects drug clearance, oxygen demand, acid base status, as well as induction time and recovery, are highly temperature dependent. 2,8,17,23,31 Hypothermia leads to a progressive decrease in cardiac output and an increase in cardiac shunting. 8 This ability to selectively shunt blood flow away from pulmonary circulation is likely the cause of prolonged recovery from inhalant anesthesia in the reptile patient. 31 In anesthetized garter snakes ( Thamnophis sirtalis parietalis ), recovery time at 21ºC (69.8ºF) was twice as long as at 31ºC (87.8ºF). 2,25 Maintain body temperature within the preferred optimum temperature zone (POTZ) for your species of interest during anesthesia and recovery. 2,21 Although POTZ is species specific, 25-35ºC (77-95ºF) will be appropriate for most temperate and tropical squamates during induction, anesthesia, and recovery. 2 Many freshwater turtles will tolerate temperatures between 20-25ºC (68-77ºF), while sea turtles and land tortoises are better adapted to temperatures between 25-30ºC (77-86ºF). 20,31 Monitor reptiles carefully during recovery to prevent overheating and/or burns. 17,31 Thermal burns can occurmore easily in reptiles that are dehydratedwith poor peripheral perfusion. 2 Although low ambient temperatures will slow or halt reptile activity, hypothermia should never be considered part of the anesthesia or sedation protocol. Heart rate Changes in this vital sign can be a sensitive clue to the physiologic status of the patient (Table 4). 9 There is no clinical consensus over when bradycardia or tachycardia should be treated, but conservative guidelines for intervention are approximately 20% below or 20% above normal. 9 Both bradycardia and tachycardia should always be addressed when associated with evidence of poor cardiac output, reduced blood pressure , or inadequate tissue perfusion. Leading Article >>> 10 Table 3. Forms of thermal support during anesthesia (Skorupski et al 2017) Increase ambient temperature of prep and surgical areas Follow surgical prep with sterile saline instead of alcohol Provide clear plastic drapes for additional insulation Minimize surgical time and surgical preparation time Warm flushing solutions Appropriate use of thermal support such as circulating hot water blankets, convective forced air warming devices, warm water bottles (wrapped in towels to minimize burns), and even bubble wrap Use radiant heat lamps with EXTREME caution only