Comparison of three different methods to prevent heat loss in healthy dogs undergoing 90 minutes of general anesthesia.

Objective To compare a towel under, a warm water pad under or a forced warm air blanket over dogs as techniques to reduce heat loss during a standardized anesthetic. Study design Prospective, randomized, crossover study. Animals Eight, healthy, mixed breed dogs weighing 16.319.6kg. Methods Dogs were anesthetized four times for 90minutes. Dogs were placed on a steel table (treatment TA), with a cotton towel (treatment TO) or a circulating warm water pad (treatment WP) between the dog and the table, or with, a towel under the dog and covered with a forced warm air blanket (treatment WAB). Rectal temperature (RT) was recorded at 5minute intervals. Changes in temperature (RT) were calculated as the RT at a given point subtracted from the RT before anesthesia (baseline) and compared over time. Results After 90minutes of anesthesia, the RT was 3.42 degrees C +/- 0.29 for TA, 2.78 degrees C +/- 0.43 for TO, 1.98 degrees C +/- 0.29 for WP, and 0.91 degrees C +/- 0.27 for WAB. Significant differences in RT occurred between TA and WAB at 20minutes (0.94 degrees C +/- 0.42, p=0.0206), between TO and WAB at 30minutes (1.16 degrees C +/- 0.62, p=0.0063), between WP and WAB at 50minutes (0.96 degrees C +/- 0.98, p=0.0249), between TA and WP at 35minutes (1.19 degrees C +/- 0.54, p=0.0091), between TO and WP at 70minutes (1.12 degrees C +/- 0.56, p=0.0248), and between TA and TO at 75minutes (0.96 degrees C +/- 0.62, p=0.0313). These differences in RT between each treatment persisted from the times indicated until the end of the anesthesia. Conclusion and clinical relevance During anesthesia, forced warm air blankets were superior to other methods tested for limiting heat loss. An efficient heat loss technique should be used for anesthesia longer than 20minutes duration in medium sized dogs.