March 1, 2022

Audience: Executive Leadership, Shelter/Rescue Staff & Volunteers, Veterinary Team

Organization: Cornell University
Investigator(s): Dr. Galina Hayes
Grant Amount: $10,767.00
Project Type: Basic Research
Project Status: Research Complete

Project Summary

This Cornell University study was a prospective observational study conducted at five animal high-quality high-volume spay/neuter (HQHVSN) shelters located in the upstate New York area, to investigate the incidences of perioperative inadvertent hypothermia (PIH) in dogs undergoing spay or neuter and cats undergoing spay surgeries. PIH occurs in cats and dogs when core temperatures fall below 36 degrees Celsius (96 degrees Fahrenheit) in association with anesthesia and surgery (Redondo et al. 2012). This may occur due to radiant, conductive or evaporative heat loss in conjunction with anesthesia related vasodilation and loss of normal mechanisms to regulate body temperature. Several negative secondary effects of PIH in small animals have been identified, including prolonged anesthetic recovery (Rodriguez-Diaz et al. 2020) and prolonged post-operative anorexia (Rodriguez-Diaz et al. 2020). Incidences of PIH in humans, particularly infants, have prompted PIH to be made the subject of quality improvement initiatives, but less so in veterinary care settings.


The objective of the project was: To determine the incidence of PIH, defined as a rectal temperature of less than 36.0 degree Celsius, in a HQHVSN setting with facilities typical of those seen in primary care practice, and to assess for associations between environmental temperature and PIH incidence in this surgical population and setting. A secondary objective was to assess for associations between PIH and anesthesia recovery times and post-operative pain levels.


This was a prospective observational study conducted at five animal HQHVSN shelters located in the upstate New York area, enrolling dogs undergoing spay or neuter and cats undergoing spay surgeries performed by experienced shelter veterinarians. Thermal care was provided at the discretion of the clinical personnel, which consisted of blankets and electric heating pads, and only used routinely in the immediate post-operative period. Data collection was performed by a single individual following a written protocol and using an electronic data entry system. Animals' breathing tubes were removed once they were able to swallow and were showing return of jaw tone post-operatively.


  • 140 dogs undergoing 65 neuters and 75 spays, and 161 cats were enrolled
  • Mean surgical times were 19.6+/-8.0 minutes (dog spays), 7.2+/-3 minutes (dog neuters) and 10.6+/-3.6 minutes (cat spays)
  • PIH incidences was 21.9% (95% CI=17.3-26.6)
  • The risk in both cats and dogs of developing PIH was associated with environmental temperature, with 22% increase in the likelihood of experiencing PIH for each degree centigrade decrease in environmental temperature (OR=1.22, 95% CI=1.03-1.44, p=0.02) over a recorded range of 15.6-26.1 degrees Celsius. In cats, PIH was associated with a prolongation of time to remove tubes by 3.8 minutes (95% CI2.27-5.37, p=0.01).


This study identified that PIH is common in a HQHVSN shelter setting with limited manpower and equipment, and that incidence is associated with environmental temperatures. Raising the ambient environmental temperature to around 23 degrees Celsius may be a simple, low-cost measure to reduce incidence and improve outcomes, including anesthesia recovery times. It should be noted that this study suffered from several design limitations, such as observations during only one season of the year (summer) and the possibility of an observer's presence altering clinical behavior. Such factors limit the conclusions that can be drawn.


  1. Redondo, J.L., Suesta, P., Serra, I., et al (2012) Retrospective study of the prevalence of postanesthetic hypothermia in dogs. Veterinary Record 171, 374
  2. Redondo JL, Suesta P, Gil, L., et al (2012) Retrospective study of the prevalence of post anesthetic hypothermia in cats. Veterinary Record 170, 206
  3. Rodriguez-Diaz, J., Hayes, G., Boesch, J. et al (2020) Decreased incidence of perioperative inadvertent hypothermia and faster anesthesia recovery with increased environmental temperature: A nonrandomized controlled study. Veterinary Surgery 49:256-264