Rapid core-to-peripheral tissue heat transfer during cutaneous cooling

Area of Science:

• Anesthesiology
• Thermoregulation
• Physiology

Background:

• Perioperative thermal management often relies on surface methods due to invasiveness of core warming techniques.
• Effective heat transfer between peripheral and core body compartments is crucial for modulating core temperature changes.
• Understanding heat flow dynamics is essential for optimizing perioperative temperature control strategies.

Purpose of the Study:

• To investigate whether core hypothermia is delayed following the initiation of surface cooling in anesthetized volunteers.
• To quantify the rate of heat loss from peripheral and core tissues during active surface cooling.
• To assess the degree of heat flow restriction between peripheral and core compartments under specific anesthetic conditions.

Main Methods:

• Six volunteers underwent anesthesia with propofol and midazolam, followed by passive insulation.
• Skin surface cooling was induced using forced air (10°C, 1000 L/min).
• Heat balance was calculated from cutaneous heat loss and metabolic heat production; tissue temperatures were monitored using intramuscular thermocouples and skin sensors.

Main Results:

• Core body temperature decreased at a rate of approximately 1.3°C/h with no delay after initiating surface cooling.
• Peripheral (arm and leg) and core (trunk and head) tissue heat content decreased at similar rates (approx. 50 kcal/h and 47 kcal/h, respectively).
• Overall body heat content decreased by approximately 234 kcal during 2.5 hours of active cooling.

Conclusions:

• Surface cooling effectively and promptly reduces core body temperature in anesthetized individuals.
• There is minimal restriction to heat flow between peripheral and core tissues in vasodilated, anesthetized subjects.
• These findings suggest efficient thermal exchange, supporting the efficacy of surface cooling for inducing hypothermia in this context.