Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update

Area of Science:

• Physiology
• Pathophysiology
• Environmental Medicine

Background:

• Accidental hypothermia (AH) is defined as a body core temperature (BCT) below 35°C.
• This review updates the understanding of physiological and pathophysiological changes during AH and rewarming from hypothermic cardiac arrest (HCA).

Purpose of the Study:

• To provide an updated overview of the physiological and pathophysiological changes associated with accidental hypothermia.
• To discuss the implications for rewarming from hypothermic cardiac arrest.

Main Methods:

• Review of physiological responses to cold exposure.
• Analysis of metabolic, cardiovascular, coagulation, and renal changes in hypothermia.
• Discussion of factors influencing outcomes in hypothermic cardiac arrest.

Main Results:

• Cold exposure triggers hormonal responses (TRH, TSH, prolactin) influencing metabolism via brown adipose tissue (BAT).
• Metabolism decreases by 7% per °C drop in BCT, reducing cardiac output (CO) but potentially allowing adequate oxygen delivery with CPR.
• Hypothermia impairs coagulation and renal blood flow, and can exacerbate rhabdomyolysis in trauma patients.

Conclusions:

• Adequate oxygen delivery may be maintained during hypothermia with effective CPR.
• Rewarming is essential for HCA victims, but specific criteria (e.g., high potassium, prolonged burial) may indicate futile resuscitation.
• Understanding these physiological changes is critical for managing AH and HCA.