Knowing what happens during stage four of cold water immersion is critical for survival. This is the stage where the human body begins to lose heat, resulting in long-term hypothermia. If the person remains in the water for too long, the cold water will draw out the person’s heat and cause cardiac arrest or loss of consciousness. This stage may also result in post-immersion collapse, when the person loses consciousness and starts to stop breathing.
True hypothermia occurs after 30 minutes of immersion in cold water. Unfortunately, about 75% of those victims do not reach this stage. The victim is usually unconscious regardless of how severe the hypothermia is. The victim’s core body temperature drops to dangerously low levels, and they are unlikely to survive. Depending on the circumstances of their cold water immersion, the person may experience death within 30 minutes or less.
The most common causes of cold water immersion are falling overboard or capsizing. Keep your boat low and load it evenly to avoid falling overboard. Try to get out of the water as quickly and safely as possible. If the situation hasn’t been avoided, the time to swim will be reduced by up to three minutes. After 30 minutes, the ability to swim will no longer be there. To prevent this, remain calm, conserve energy, and maintain body heat.
Within five to fifteen minutes, the cold water immersion stage begins. To preserve core heat, the body begins to vasoconstrict. This restricts blood flow to the extremities, preventing blood from reaching vital organs. This causes a loss in mobility which is vital for survival. This stage of cold water immersion can lead to death if you don’t have a life jacket. There are several different stages, each with varying degrees of risk.
After the first two stages of cold water immersion, true hypothermia becomes a major contributing factor in death. The patient’s core temperature drops, but this is only at 30 minutes. The body’s normal defense mechanisms fail to keep the patient safe and warm. Hypothermia develops as a result of the combined effects of the cold water and diuresis. The patient’s peripheral blood pressure may also not be able increase.
Once a patient has reached the onset of hypothermia, the paramedic needs to know about the four stages of cold water immersion. This includes the cold incapacitation, hypothermia and circum-rescue collapse. An assessment should aim to maximize patient oxygenation. Although good ventilation should be the foundation of management of immersion, it’s important to consider other injuries and secondary surveys.
The third stage is abrupt and can last for days or even weeks. It can take anywhere from six to ten weeks. The affected extremity becomes edematous and bright red, reflecting a delayed capillary refill. Pain is intense, although the distal portions of the affected extremity may still be anemic. Tissue damage is rarely visible, but nonviable areas may become blistered or develop necrosis.