Effect of prewarming on the body temperature of small dogs undergoing inhalation anesthesia

To investigate whether prewarming affects body temperature of small dogs (weighing < 10 kg [22 lb]) undergoing inhalation anesthesia.

Prospective, randomized, blinded clinical trial. Animals: 20 dogs weighing < 10 kg with American Society of Anesthesiologists physical status I or II.

Baseline rectal temperature was recorded. Before IM administration of buprenorphine hydrochloride and acepromazine maleate, dogs were randomly assigned to be placed in a pediatric incubator at 33°C (91.4°F) for approximately 30 to 60 minutes (prewarming group) or to receive no prewarming (control group); subsequently, dogs underwent inhalation anesthesia with isoflurane in oxygen. Rectal, esophageal, and ambient temperatures were measured every 5 minutes from induction of anesthesia (IOA) for > 1 hour by an observer who was unaware of treatment. If a dog became hypothermic (esophageal temperature < 36°C [96.8°F]), it was withdrawn from the study. Variables of interest relating to dogs, anesthesia, temperatures, hypothermia, and study withdrawal were compared between groups.

1 dog was excluded from the prewarming group after becoming excessively excited in the incubator. Between groups, age, weight, body condition score, degree of preanesthesia sedation, interval from sedation to IOA, duration of anesthesia, baseline rectal temperature, rectal temperatures immediately prior to IOA, esophageal temperature following IOA, ambient temperature during the first 70 minutes of anesthesia, esophageal or rectal temperature during the first 90 minutes of anesthesia, and incidence of hypothermia and study withdrawal (5 dogs/group) did not differ significantly.

Prewarming in an incubator prior to IOA failed to improve or maintain body temperature of dogs weighing < 10 kg during inhalation anesthesia.