rewarming

Rewarming is the process of increasing body temperature after exposure to cold or after hypothermia. In medicine, it aims to restore normothermia and prevent complications. Rewarming can be passive or active, external or internal. Passive rewarming relies on the body’s own heat production and environmental insulation, such as blankets and a warm environment, with minimal intervention. Active external rewarming uses devices that deliver heat to the body's surface, such as warming blankets or forced-air systems. Active internal rewarming delivers heat directly to the body's core through warmed intravenous fluids, heated humidified oxygen, or gastric or peritoneal lavage. In severe cases, extracorporeal rewarming uses the patient's blood heated outside the body via techniques like ECMO or cardiopulmonary bypass.

Guidelines emphasize controlled, gradual warming. The target rate of core temperature rise depends on the severity of hypothermia; typical rates range from 0.5 to 2.0 degrees Celsius per hour for mild cases, and slower for severe cases. Core temperatures are monitored with rectal, esophageal, or bladder probes. During rewarming clinicians watch for afterdrop, a continued fall in core temperature during warming due to return of cold peripheral blood, and for rewarming shock, electrolyte disturbances, and dysrhythmias.

Electrolyte management, acid–base balance, and careful monitoring of hemodynamics are important. In frostbite management, rewarming is typically performed in a controlled setting and guided by tissue viability and the availability of definitive care. In general, external exposures are treated promptly with gradual warming to minimize tissue injury. Rewarming principles are integrated into protocols for hypothermia, cardiac arrest with hypoxic injury, and accidental immersion injuries, with settings tailored to patient needs.