Higher Room Temperature Combats Perioperative Hypothermia

In human medicine, perioperative inadvertent hypothermia (PIH) is associated with higher infection rates, reduced immune function, increased discomfort, and prolonged recovery.^1-3 Increasing ambient temperature in induction and surgical areas can help decrease the risk for PIH in pediatric patients.⁴

This hospital protocol study from Cornell University evaluated hypothermia in canine (n = 277) and feline (n = 20) patients undergoing general anesthesia for open surgery. Data were compared under 3 different PIH prevention protocols: baseline, baseline and raised environmental temperatures (75°F [24°C]), and a new thermal care protocol with raised environmental temperatures (75°F [24°C]). Baseline data were collected for the hospital’s standard prestudy warming measures, including active (ie, forced air blanket, circulating water beds, warmed lavage fluid) and passive (ie, blanket) warming techniques at anesthetist discretion. The new thermal care protocol implemented specific warming techniques when patient temperatures dropped below 100.5°F (38°C) during premedication or below 101°F (38.3°C) postinduction.

In the baseline group, mean induction and operating room temperatures were 70.1°F (21.2°C) and 65.5°F (18.6°C), respectively. Hypothermia was documented in 35.6% of these patients and was more likely to occur in cats (50%) than in dogs (35.1%). The greatest drop in body temperature occurred between induction and start of surgery, which took a median of 59 minutes. Increasing room temperature to 75°F (24°C) reduced incidence of hypothermia to 13% without changing the baseline warming protocol. No additional decrease in PIH was detected after adding the new thermal care protocol to the elevated ambient temperature. Patients from rooms at 75°F (24°C) were extubated faster (ie, 5 minutes) than patients in nonwarmed rooms (ie, 7 minutes).

Other factors associated with greater PIH risk included larger clip sites (Figure) and preoperative imaging during the same anesthetic episode. For each 9% increase in body surface area clipped, the odds for hypothermia increased by 1.82. Preoperative imaging under anesthesia was associated with a 5.72 times increased risk for hypothermia. Duration of surgery/anesthesia was not associated with increased risk.

Key pearls to put into practice:

In addition to active monitoring and treatment of PIH, raising temperatures in induction and operating areas to 75°F (24°C) reduced the incidence of hypothermia by >50%. This is an easy and effective intervention that can be instituted to combat PIH.

Measures to reduce time between induction and surgery, particularly after patients have been clipped and scrubbed, may reduce the risk for hypothermia. Patient preparation exposes moistened skin to air, causing evaporative cooling. Monitoring patient temperatures and using warming measures during this interval should not be discounted.

Performing preoperative imaging under premedication instead of under general anesthesia may reduce the risk for hypothermia.