Maintain dogs’ presurgery warmth to avoid hypothermia

By Sarah Guy, medwireNews Reporter

Hypothermia is common in dogs after undergoing surgery under anesthetic, especially for diagnostic procedures and when the animal is in poor condition, research indicates.

Smaller dogs, those undergoing lengthy surgeries, and those receiving thoracic surgery are also all at increased risk for postoperative hypothermia, say the researchers.

Conversely, the study results show that a higher baseline (preoperative) body temperature was a significant protective factor against hypothermia in dogs, suggesting that increasing operating room temperatures may prevent heat loss during procedures.

"Consequently, basic preventive measures would be to accelerate the animal's preparation during the preanesthetic time, and to shorten the procedure if possible," remark Rafael Gómez-Villamandos (Universidad de Córdoba, Spain) and colleagues in Veterinary Record.

The team reviewed the anesthetic records of 1525 dogs, aged a mean of 3.8 years and weighing a mean of 18.0 kg, which were treated in a hospital with controlled air conditioning at 20-25ºC.

After the procedures, 2.9% of dogs had hyperthermia (>39.50ºC), 14.4% had normothermia (38.50ºC-39.50ºC), 51.5% had slight hypothermia (38.49ºC-36.50ºC), 29.3% had moderate hypothermia (36.49ºC-34.00ºC), and 2.8% had severe hypothermia (<34.00ºC), report the researchers.

Multiple regression analysis revealed that higher temperature before surgery (mean 38.7ºC) independently predicted an increased temperature at the end of the procedure, while lower body surface area also predicted increased temperatures postanesthetic.

"Smaller animals have a relatively large surface area in relation to body weight, so proportionally, more heat is lost through their skin, leaving them more susceptible to perioperative hypothermia than larger animals," write Gómez-Villamandos and co-investigators.

They found several variables significantly associated with a decrease in postsurgery temperature, including longer preanesthetic time, longer duration of anesthesia, worse physical condition (American Society of Anesthesiologists [ASA] criteria III and IV dogs had lower temperatures than ASA I dogs), the reason for the anesthesia (diagnostic procedures and thoracic surgery induced lower postprocedure temperatures than more minor operations), and the recumbency of the animal during anesthesia (sterna- and dorsal-induced lower temperatures than lateral recumbency).

Finally, the time to extubation was significantly longer among dogs that developed severe hypothermia compared with animals in all other groups, note the authors.

"Anesthetics inhibit thermoregulation in a dose-dependent manner, and inhibit vasoconstriction and shivering," explains the team.

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