Hypothermia: Core Temperature Thresholds and Organ Failure

Stages of Hypothermia

Stage	Core Temp	Key Features
Mild	35–32°C (95–90°F)	Shivering, vasoconstriction, tachycardia, tachypnea, mild confusion
Moderate	32–28°C (90–82°F)	Shivering stops, muscle rigidity, bradycardia, hypotension, atrial fibrillation, marked confusion, lethargy
Severe	<28°C (<82°F)	Loss of consciousness, absent reflexes, fixed dilated pupils, ventricular fibrillation/asystole, apparent death

Critical Thresholds

• <35°C (95°F): Hypothermia defined; active rewarming indicated.
• <32°C (90°F): High risk of lethal arrhythmias; handle gently, avoid rough movement.
• <28°C (82°F): May appear dead; “no one is dead until warm and dead” – continue CPR during rewarming.

Rewarming Methods

• Passive (insulation) for mild.
• Active external (forced-air warming blankets) for moderate.
• Active core (warmed IV fluids, pleural/peritoneal lavage, ECMO) for severe.

Prevention: layered clothing, shelter, nutrition, avoid alcohol in cold.