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Table 1 Mechanisms of heat transfer in trauma

From: A recommended early goal-directed management guideline for the prevention of hypothermia-related transfusion, morbidity, and mortality in severely injured trauma patients

Mechanism

Rate (kcal/h)

Description

Radiation

10–50

Transfer of heat energy via electromagnetic waves down a concentration gradient without direct contact according to Boltzmann’s equation:a Q = K(T1 – T2)

  

Methods to reduce losses include:

  

 • warming blankets

  

 • increasing environmental temperature

  

 • radiant heaters

  

 • avoid unnecessary anesthesia

Conduction

16–30

Transfer of energy between two solid objects in contact according to Fourier’s equation:b Q = KA dt/dx

  

Methods to reduce losses:

  

 • removal of wet clothing

  

 • avoid prolonged contact with cold surfaces

Convection

10–20

Transfer of heat energy during the mass movement of gas or liquid.

Evaporation

12–16

Heat energy transferred during change of phase (water to gas): 58 kcal/g water evaporated from skin, respiratory tract, and viscera

  

Methods to reduce losses for convection and evaporation:

  

 • avoid prolonged surgery with an open abdomen

  

 • warming blankets

  1. a Q = rate of radiant heat transfer, K = a constant, T1 = temperature of the first object, T2 = temperature of the second object
  2. b Q = rate of heat transfer by conduction, K = thermal conductivity, A = area in contact, dt/dx = thermal gradient
  3. Adapted with permission from [71]