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Warm Up to Hypothermia Prevention


Four Mechanisms Heat Loss

  1. Radiationthe Number 1 cause of heat loss in the Operating Room (for example the transfer of body heat in the form of infrared radiant energy).
  2. Convection - loss of body heat to the ambient cooler air.
  3. Conduction - direct flow of body heat to a cooler supporting surface.
  4. Evaporationwarmed body moisture carries with it body heat upon evaporation.


Heat loss upon induction of anesthesia

  • Immediate vasodilation of blood vessels in the periphery skin, legs, tail
  • Shunting or transfer of warmer blood from the core to the colder periphery
  • Patient becomes a heat radiator


Three phases of hypothermia during general anesthesia (refer to diagram)

Phase 1

  • Rapid decrease in body temperature in the first hour (starts upon induction)
  • Due to the redistribution of blood flow to the periphery
  • ****81 Percent of Heat Loss That Will Occur****

Phase 2

  • Clow decline of body temperature in the next 2 to 4 hours
  • Heat loss exceeds metabolic heat production by 20 to 40 percent

Phase 3

  • Core temperature stability
  • Metabolic heat production equals heat loss

temp loss for animals during anesthesia


Preoperative Warming

  • 81 Percent of heat loss occurs in the first hour after anesthetic induction
  • ****Most Important Time to Start Active Warming and Heat Retention****

****Minimize delay between pre-op and intra-op warming. For every minute of delay, the likelihood of a drop in core body temperature is increased by 5 percent ****

Intraoperative Warming

  • Use active warming on as large a patient surface area as possible
  • Implement measures to retain body heat
  • Minimize time from pre-op to intra-op warming

Postoperative Warming

  • Continue active warming and heat retention until the patient is fully awake


TAKEAWAY – Start warming pre-op immediately upon anesthesia induction and minimize the delay between pre-op and intra-op warming

For a complete Veterinary webinar on Hypothermia go to:

Resource Center - VetORSolutions