Temporal changes in core body temperature in anesthetized adult horses

Michael Tomasic From the Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348-1692.

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Abstract

Objective

To examine temporal patterns of core body temperatures in adult horses during general anesthesia and to determine the efficacy of forced-air warming blankets in attenuating decreases in core body temperatures.

Animals

5 clinically normal adult horses.

Procedure

Horses were assigned to each of 2 trials, warmer and no-warmer, in a randomized crossover design. Horses were instrumented with a thermistor-tipped pulmonary arterial catheter to measure core body temperature. Induction and maintenance of and recovery from general anesthesia were performed in an air-conditioned surgical suite where room temperature and relative humidity were maintained at approximately 21 C and 40%, respectively. Core body temperature measurements were recorded every 5 minutes during 2.5 hours of anesthesia and during recovery until horses could stand. Data were analyzed, using ANOVA for repeated measures.

Results

Without warming, mean core body temperature decreased steadily (0.37 ± 0.18 C/h). Forced-air warming significantly decreased that rate to 0.19 ± 0.09 C/h. In both trials, there was an additional, rapid, significant decrease in core body temperature when horses were moved to the recovery area, which was apparently the result of conductive heat loss to the cold floor. Recovery time and time required for core body temperature to return to baseline were unaffected by forced-air warming during anesthesia and recovery.

Conclusions and Clinical Relevance

Core body temperature decreases steadily in adult horses anesthetized in a cool, dry environment. Forced-air warming devices can attenuate this decrease. Additional body heat can be lost rapidly when anesthetized horses are positioned on cold surfaces during recovery. (Am J Vet Res 1999;60:556–562)

Abstract

Objective

To examine temporal patterns of core body temperatures in adult horses during general anesthesia and to determine the efficacy of forced-air warming blankets in attenuating decreases in core body temperatures.

Animals

5 clinically normal adult horses.

Procedure

Horses were assigned to each of 2 trials, warmer and no-warmer, in a randomized crossover design. Horses were instrumented with a thermistor-tipped pulmonary arterial catheter to measure core body temperature. Induction and maintenance of and recovery from general anesthesia were performed in an air-conditioned surgical suite where room temperature and relative humidity were maintained at approximately 21 C and 40%, respectively. Core body temperature measurements were recorded every 5 minutes during 2.5 hours of anesthesia and during recovery until horses could stand. Data were analyzed, using ANOVA for repeated measures.

Results

Without warming, mean core body temperature decreased steadily (0.37 ± 0.18 C/h). Forced-air warming significantly decreased that rate to 0.19 ± 0.09 C/h. In both trials, there was an additional, rapid, significant decrease in core body temperature when horses were moved to the recovery area, which was apparently the result of conductive heat loss to the cold floor. Recovery time and time required for core body temperature to return to baseline were unaffected by forced-air warming during anesthesia and recovery.

Conclusions and Clinical Relevance

Core body temperature decreases steadily in adult horses anesthetized in a cool, dry environment. Forced-air warming devices can attenuate this decrease. Additional body heat can be lost rapidly when anesthetized horses are positioned on cold surfaces during recovery. (Am J Vet Res 1999;60:556–562)

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