During stage 4 of cold water immersion, what is a critical risk after rescue?

In stage 4 of cold water immersion, the body wears down as hypothermia continues to progress, and one of the critical risks after rescue is the collapse of arterial blood pressure. During this stage, the body's core temperature drops significantly, leading to impaired cardiovascular function. When rescued, many individuals may experience a sudden physiological response due to factors such as rewarming and the effects of cold exposure on their circulatory system.

The collapse of arterial blood pressure can occur because of a combination of vasodilation, where blood vessels expand as the body rewarms, and reduced heart function due to the cold. This can lead to dangerous complications like shock or even cardiac arrest if not managed properly. The priority in such situations is addressing the cardiovascular stability of the individual before moving on to treat symptoms such as shivering or muscle fatigue, which may seem significant but are secondary to the immediate threat of unstable blood pressure.