A second postcooling afterdrop: more evidence for a convective mechanism

Area of Science:

• Physiology
• Sports Medicine
• Environmental Health

Background:

• Core temperature afterdrop, a decrease in core temperature after removal from a cold environment, is a significant concern in managing hypothermia.
• The mechanisms driving afterdrop, particularly the role of peripheral tissue perfusion, require further elucidation for effective treatment strategies.

Purpose of the Study:

• To investigate the impact of rewarming methods on core temperature afterdrop following cold water immersion.
• To determine if increased perfusion of cold peripheral tissues contributes to the core temperature afterdrop phenomenon.

Main Methods:

• Five male subjects underwent two cold water immersion (8°C) trials, followed by rewarming via either shivering thermogenesis or treadmill exercise.
• Esophageal and muscle temperatures (thigh and calf) were monitored throughout the cooling and rewarming phases.
• Core temperature afterdrop and rewarming rates were analyzed in relation to the rewarming method employed.

Main Results:

• Core temperature afterdrop was significantly greater (58%) following exercise-induced rewarming compared to shivering thermogenesis.
• Rewarming rates in a warm bath (40°C) were attenuated, with a secondary afterdrop observed in some trials.
• A potential correlation between increased peripheral tissue perfusion and the attenuation or reversal of initial rewarming was identified.

Conclusions:

• Increased perfusion of cold peripheral tissues is a likely contributor to core temperature afterdrop and the subsequent attenuation of rewarming.
• These findings have critical implications for the clinical management of hypothermia, emphasizing the need to consider peripheral circulation during rewarming.
• Optimizing rewarming strategies may involve managing peripheral tissue perfusion to mitigate afterdrop and improve patient outcomes.