The benefit of thermal support for canine anesthetic patients has been demonstrated to reduce the risk of decreased core body temperature during anesthetic episodes. Several factors can contribute to patient hypothermia during general anesthesia, including cold operating rooms, cold equipment, and decreased physiologic thermoregulation.
Several of the pharmaceuticals used during anesthesia – including several sedative agents – can make the hypothalamus less responsive to a decrease in body temperature. Alpha-2s lead to vasoconstriction while volatile inhalant anesthetics may lead to vasodilation. Hypothermia also can slow drug metabolism during the anesthetic episode.
For these reasons, external heat sources are often utilized during episodes of general anesthesia. Today, a variety of commercially external heat support sources are available, including heated surgical tables, warm-water circulating blankets, and warm-air circulating systems. Each of these has the common function of providing surface warmth to the contact area with the patient.
It is essential to use devices that have been demonstrated as safe and effective for use in unconscious patients. The patient under anesthesia is unable to move away from excessive heat, which may lead to thermal injury to the skin and subsequent tissue necrosis. The use of items heated in a microwave such as warming discs, rice socks, fluid bags, gloves, or bottles may result in thermal injury. Additionally, direct heating sources such as electrical heating pads are not appropriate for this purpose.
The use of appropriate heating sources should be monitored throughout the anesthetic episode for evidence of excess moisture, temperature changes, or other signs of malfunction. Extended anesthetic episodes, thin skin, and pressure at points of contact can all increase the risk for thermal injury. A temperature sensor should be used consistent with the directions for use of any heating device. Temperature readings should be included in the anesthesia report.
In this case, Dr. B was found to be below the standard of care due to the use of an inappropriate device. The insurance carrier settled the case with the owner for $6,200. The carrier also paid $1,800 in legal defense costs associated with the claim on behalf of Dr. B.
Pottie RG, Dart CM, Perkins NR, Hodgson DR. Effect of hypothermia on recovery from general anaesthesia in the dog. Aust Vet J. 2007 Apr;85(4):158-62. doi: 10.1111/j.1751-0813.2007.00128.x. PMID: 17397389.
2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats, Journal of the American Animal Hospital Association, 2020Mar/Apr; 56(2); accessed online 2/14/2022 https://www.aaha.org/globalassets/02-guidelines/2020-anesthesia/anesthesia_and_monitoring_guidelines_final.pdf