Today's Veterinary Practice

MAY-JUN 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 74 FOCUS ON MONITORING DURING TREATMENT Monitoring during treatment for hypothermia should consist of blood pressure monitoring and electrocardiography, as well as measurement of blood glucose, electrolytes, and hematocrit. Peripheral vasoconstriction can affect blood pressure and make readings unreliable with use of indirect methods. The hematocrit will increase by 2% for every 1°C (1.8°F) drop in core body temperature. A coagulation panel, lactate levels, and oxygen saturation by pulse oximetry should also be monitored, but vasoconstriction may affect the usefulness of pulse oximetry.2 Do not turn the animal side to side as a form of stimulation because the change in body position results in an acute drop in blood pressure or gastric reflux in some animals.8 COMPLICATIONS FROM HYPOTHERMIA Because an animal recovering from anesthesia may experience hypothermia, it must be treated appropriately to improve patient recovery and decrease potential morbidity. Several complications can occur with hypothermia. For example, impaired cardiovascular function may develop, with decreased cardiac output that leads to vasoconstriction. When the animal is rewarmed, vasodilation can enhance hypovolemia and lead to shock. Cardiac arrhythmias can occur at body temperatures of 31°C (87.8°F) or less. Hypothermia can cause hypoventilation, necessitating ventilator support, and liver metabolism and renal excretion of anesthetic drugs are slower because of the decrease in liver and renal blood flow. This may prolong recovery and lead to weakness in recovery. Animals with hypothermia may also have decreased resistance to infection and increased incidence of surgical wound infection. Other complications include decreased oxidative killing by neutrophils, reduction of phagocytosis, and suppression of leukocyte migration. The vasoconstriction and increased blood viscosity decrease oxygen delivery to tissues, contributing to poor wound healing. The increased blood viscosity and slowing of enzymatic reactions of the coagulation pathways can lead to coagulopathy and increased blood loss. There is also increased postoperative protein catabolism. Shivering increases metabolism and heat production, but also increases myocardial oxygen demands and glucose needs. 3,5 These adverse effects can be minimized with appropriate thermal support for the anesthetized patient. See TABLE 1 for the 4 mechanisms of heat loss. It is also important to remember the following: ■ Radiation and convection are the most important causes of heat loss and can account for 80% of the total heat losses in patients. ■ Keeping the air temperature around the patient warm will decrease heat loss. ■ Most types of heat loss depend on amount of exposed skins; minimizing skin exposure can reduce heat loss. 4 References 1. Clark-Price S. Inadvertent perianesthetic hypothermia in small animal patients. Vet Clin North Am Small Anim 2015;45(5):983-994. 2. Todd JM. Hypothermia. In: Silverstein DC, Hopper K (eds). Small Animal Critical Care Medicine. 2 nd ed. St. L ouis: Elsevier Saunders; 2015:789- 795. 3. Lagutchik MS, Ford A. Care of the environmentally injured animal. In: Burkitt-Creedon JM, Davis H (eds). Advanced Monitoring and Procedures for Small Animal Emergency and Critical Care. Ames, IA: Wiley-Blackwell; 2012:799-813. 4. Ko JC. Anesthesia monitoring and management. In: Ko JC (ed). Small Animal Anesthesia and Pain Management. L ondon: Manson Publishing; 2013:123-162. 5. Posner LP. Troubleshooting hypothermia and hyperthermia. In: Smith LJ (ed). Questions and Answers in Small Animal Anesthesia. Ames, IA: Wiley Blackwell; 2016:147-153. 6. Ko JC. Anesthesia monitoring and management. In: Ko JC (ed). Small Animal Anesthesia and Pain Management. L ondon: Manson Publishing; 2013:123-162. 7. Hackett TB. Physical examination and daily assessment of the critical ill patient. In: Silverstein DC, Hopper K (eds): Small Animal Critical Care Medicine. 2 nd ed. St. Louis, MO: Elsevier Saunders; 2015:6-10. 8. Clarke KW, Trim CM, Hall LW. Anesthesia of the dog. In: Clarke KW, Trim CM, Hall LW (eds). Veterinary Anesthesia. 11 th ed. St Louis, MO: Elsevier Saunders; 2014:405-498. 9. Ko JC. Anesthetic emergencies and cardiopulmonary resuscitation. In: Ko JC (ed). Small Animal Anesthesia and Pain Management. London: Manson Publishing; 2013:173-186. Jane Quandt Jane is associate professor of comparative anesthesia at the University of Georgia College of Veterinary Medicine. She received her DVM from Iowa State University and her master's degree in anesthesia from the University of Minnesota. She has diplomate status with the American College of Veterinary Anesthesia and Analgesia and American College of Veterinary Emergency and Critical Care.

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