Warm Up to Hypothermia Prevention – Quick Takeaways

Quick Takeaways: 

Four Mechanisms of Heat Loss – 

1) Radiation – number one cause of heat loss in the OR 

  •  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) Evaporation – warmed 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 –

  • Phase 1
    • rapid decrease in body temperature in the first hour (starts upon induction) 
    • due to redistribution of blood flow to the periphery
    •  ****81 Percent of Heat Loss That Will Occur****
  • Phase 2
    • slow 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

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 the 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 delay between pre-op and intra-op warming. 

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