Examining the Relationship Between Core Temperature, Heat Balance, and Energy Expenditure.

Area of Science:

• Physiology
• Thermoregulation
• Human Metabolism

Background:

• Core body temperature is a critical physiological parameter reflecting heat balance.
• Traditional temperature studies often overlook direct measurements of metabolic heat production and heat loss.
• Quantifying net heat balance (NHB) is crucial for understanding thermoregulation.

Purpose of the Study:

• To determine if NHB can predict changes in core body temperature.
• To assess if NHB combined with skin surface temperatures (ST) can estimate core temperature.
• To investigate the impact of cooling interventions and pharmacological agents on heat balance.

Main Methods:

• Laboratory study involving healthy volunteers undergoing controlled cooling.
• Measurement of heat flux, energy expenditure (via indirect calorimetry), and deep gastrointestinal core temperature.
• Application of cooling pads with and without dexmedetomidine to modulate shivering and heat loss.

Main Results:

• NHB was found to predict core temperature changes with a lagged regression slope of 0.33°C/100W.
• Forehead skin temperature demonstrated the narrowest limits of agreement for estimating core temperature (mean bias -2.5°C).
• Cooling increased energy expenditure, partially offsetting heat loss and minimizing NHB without pharmacological intervention.

Conclusions:

• A net heat balance of -100W predicts a 0.33°C decrease in core temperature over 60 minutes.
• Forehead temperature is the most consistent peripheral site for predicting core body temperature.
• Dexmedetomidine's suppression of energy expenditure is key to achieving significant core temperature changes during cooling.