Overview: Hypothermia is a dangerous medical condition in which the core body temperature falls below 35.0 °C (95.0 °F). When the body cannot preserve heat, normal metabolic and organ functions become impaired. Hypothermia ranges from mild impairment of temperature regulation to life-threatening failure of the heart and breathing.

Signs and stages

Symptoms vary by severity. Typical features include shivering, slow or slurred speech, clumsiness or lack of coordination, confusion, drowsiness, and loss of consciousness in severe cases. Commonly described stages are:

  • Mild: core temperature slightly below normal, active shivering and mental slowing.
  • Moderate: shivering may diminish, coordination and thinking worsen, slowed pulse and breathing.
  • Severe: muscle rigidity, very slow or irregular heartbeat, loss of consciousness and risk of cardiac arrest.

Causes and risk factors

Hypothermia arises when heat loss exceeds heat production. Typical situations include prolonged exposure to cold air or water, immersion in cold water, inadequate clothing or shelter, and impaired heat generation due to age, illness, alcohol or drug use. Infants, older adults, people with certain medical conditions, and those who are wet or exhausted are at higher risk.

First aid and prevention

Immediate steps can reduce harm. Move the person out of the cold, remove wet clothing, and shelter them from wind. Rewarm gradually: use dry blankets, warm (not hot) packs to the trunk, and provide warm nonalcoholic drinks if the person is alert and can swallow. Avoid vigorous rubbing of cold limbs and do not immerse a severely hypothermic person in hot water. For any moderate or severe case, or when in doubt, seek professional care: Get medical help.

  • Prevention: appropriate clothing layers, stay dry, monitor weather, avoid alcohol in the cold, and prepare for emergencies outdoors.
  • First aid categories: passive external rewarming (blankets), active external (heating pads), and active internal methods used in medical settings.

Medical treatment and complications

Hospital care depends on severity. Treatments can include warmed, humidified oxygen; heated intravenous fluids; airway and cardiac support; and, in extreme cases, active internal rewarming techniques such as warmed lavage or extracorporeal blood warming. Complications can include cardiac arrhythmias, coagulopathy, infection, and long recovery for neurological deficits when prolonged low temperature caused tissue injury.

Notable facts: Hypothermia has long been recognized in cold-climate activities such as mountaineering and polar exploration and remains a preventable cause of morbidity and death. Prompt recognition and appropriate rewarming significantly improve outcomes, so awareness and early action are important for anyone exposed to cold environments.