Perioperative hypothermia - NYSORA | NYSORA

Perioperative hypothermia

Learning objectives

  • Describe the causes, risk factors, and consequences of perioperative hypothermia
  • Prevent and manage perioperative hypothermia

Definition & mechanisms

  • Perioperative hypothermia is defined as a core body temperature <36.0°C
  • Common consequence of anesthesia
  • Inability of the body to respond effectively to the multiple causes of heat loss during surgery and anesthesia


3 phases:

  1. Redistribution: Vasodilatation leads to warm blood reaching the peripheries and cool blood from the peripheries entering the core circulation, causing a rapid decline in temperature
  2. Heat loss exceeds heat produced from metabolism as the metabolic rate is reduced by 15-40% during general anesthesia, causing a linear decline in temperature

          Sources of heat loss:

    • Radiation
    • Convection
    • Evaporation
    • Conduction

       3. Plateau phase: Heat loss is balanced by heat produced metabolically, mostly due to maximal vasoconstriction

Risk factors

  • ASA grade 2-5 (higher grade, greater risk)
  • Preoperative temperature <36.0°C
  • Combined general and regional anesthesia
  • Major or intermediate surgery
  • At risk of cardiovascular complications 
  • Low BMI
  • Diabetic neuropathy 
  • Paraplegia
  • Severe hypothyroidism


  • Increased risk of surgical site infection
  • Decrease in drug metabolism
  • Increased bleeding and transfusion requirements
  • Increased risk of cardiac events
  • Shivering
  • Delayed discharge from post-anesthesia care unit

Prevention & management

perioperative hypothermia, temperature, metabolic heat production, active warming, forced air, resistive heating, circulating water garment devices, IV fluids, respiratory gases, post-anesthesia care unit, duvet, blankets

Suggested reading

  • Rauch S, Miller C, Bräuer A, Wallner B, Bock M, Paal P. Perioperative Hypothermia-A Narrative Review. Int J Environ Res Public Health. 2021;18(16):8749. Published 2021 Aug 19.
  • Riley C, Andrzejowski J. Inadvertent perioperative hypothermia. BJA Educ. 2018;18(8):227-233.

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