Insulating the extremities of cats with highly insulating materials during anesthesia reduces core temperature decline with additional benefit from active warming.

Objective: To evaluate whether covering the extremities of cats with highly insulating materials with or without active warming slows the rate of temperature decrease during anesthesia.

Methods: Insulating devices were created from the best insulating material-2 layers of down blanket-as determined by an in vitro study. Female cats undergoing ovariohysterectomy in a veterinary student surgical program were block randomized to active warming (insulation with heating element), passive insulation (insulation only), or control (no covering). Core body temperature was recorded every minute from induction through recovery. Multivariable linear regression was used to evaluate the rate of temperature decrease and lowest recorded temperature, controlling for weight, postinduction temperature, ambient temperature, and (for lowest temperature) anesthesia duration.

Results: 49 female cats were enrolled. In the first 30 minutes, controls decreased by 0.12 °F/min, passive by 0.11 °F/min, and active by 0.09 °F/min. After 30 minutes, temperature decline slowed, with rates of 0.05 °F/min for controls, 0.03 °F/min for passive, and 0.01 °F/min for active. The lowest recorded temperatures were 1.2 and 1.9 °F, higher in the passive and active groups, respectively.

Conclusions: Covering the extremities of cats undergoing anesthesia with highly insulating materials slows core temperature decrease.

Clinical relevance: Covering the extremities of cats resulted in a lowest temperature between 1 and 2 °F greater than controls. While active warming has a greater effect than passive insulation, the absolute difference in lowest temperature, 0.7 °F, may not justify the additional challenges of adding a heating source.