Rewarming shock
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Rewarming shock (also known as rewarming collapse) has been described as a drop in blood pressure following the warming of a person who is very cold.[1] The real cause of this rewarming shock is unknown.[1]
There was a theoretical concern that external rewarming rather than internal rewarming may increase the risk.[2] These concerns were partly believed to be due to afterdrop, a situation detected during laboratory experiments where there is a continued decrease in core temperature after rewarming has been started.[2] Recent studies have not supported these concerns, and problems are not found with active external rewarming.[2][3]
Clinical features
Patients show signs of respiratory and cardiovascular compromise due to a mismatch between oxygen supply and demand. Specific signs and symptoms include:[4]
- Hypotension
- Bradycardia
- Heart failure
- Respiratory compromise
- Acidosis
Overall, the patient is unable to regulate their body temperature resulting in a distributive shock.[4]
Pathophysiology
There is no consensus for the mechanism. In essence, rewarming shock is a failure of the body to hemodynamically and metabolically meet the needs to maintain homeostasis. Proposed mechanisms are detailed below.
Vasodilation and Venous Pooling
The process of active rewarming at a fast pace forces the body compensate by dilating its blood vessels. At a fast rate of expansion, it causes pooling in the extremities therefore releasing vast amounts of heat.[5]
Heart failure
Since the cardiovascular system is already weak due to hypothermia, the rapid dilation of blood vessels results in a significant decrease in cardiac output. This leads to a sudden decrease in blood pressure and a state of shock.[6]
Metabolic demand
At a hypothermic baseline, the cells metabolic needs are lowered yet they are still deprived from oxygen and nutrients. [7] As the rewarming process begins, the cells start increasing its metabolic needs further causing an increase in oxygen demand. Because the cardiovascular system is already weakened, it cannot keep up with the demand of the cells. [8]
