Not Medical Advice
This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional. In a medical emergency, call 911 or your local emergency number immediately.
Not Medical Advice
This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional. In a medical emergency, call 911 or your local emergency number immediately.
Hypothermia Severity Quick Reference
| Stage | Core Temp | Signs | Shivering | |---|---|---|---| | Mild | 32-35°C (89.6-95°F) | Shivering, impaired coordination, confusion | Present and vigorous | | Moderate | 28-32°C (82.4-89.6°F) | Shivering stops, muscle stiffness, stupor | Absent | | Severe | Below 28°C (82.4°F) | Unconscious, may appear dead, cardiac risk | Absent |
Field core temperature estimate: If the patient is shivering, core temp is likely above 30°C. If shivering has stopped and the patient is cold, assume moderate-to-severe.
Rewarming by Stage
Mild Hypothermia (32-35°C) — Shivering Present
The patient's own shivering mechanism is intact and working. The goal is to prevent further heat loss and support that process.
Remove from cold exposure. Wet clothing must come off — wet fabric conducts heat away 25 times faster than dry fabric. Cut clothing off rather than making the patient move their arms.
Insulate. Dry clothing, sleeping bags, emergency blankets. A vapor barrier (plastic bag, garbage bag) between the patient and the insulation prevents moisture loss. Ground insulation is critical — more heat is lost through conduction to cold ground than through the air.
Apply external heat to core zones. Chemical heat packs, warm water bottles, or another warm body pressed against the armpits, neck, and groin. Not extremities — this accelerates afterdrop.
Hot sweet drinks if conscious and able to swallow without risk of aspiration. Hot chocolate, broth, or sugar water provides calories for the shivering process. Caffeinated drinks cause vasoconstriction — acceptable.
Monitor for deterioration — if shivering stops but the patient is still cold, they've moved to moderate hypothermia.
Moderate Hypothermia (28-32°C) — Shivering Absent
The shivering mechanism has failed. The patient cannot self-rewarm. External heat must substitute.
Handle gently. Moderate hypothermic patients are in cardiac irritability. Rough handling, moving limbs vigorously, or jolting can trigger ventricular fibrillation. Move the patient horizontally, avoid sudden position changes.
Continue full insulation as above.
Active external rewarming at core zones only. Warm water bottles or heat packs in armpits, groin, and against the neck. Do not heat the extremities.
Do not give oral fluids. The patient at this stage is at risk of aspiration. No eating or drinking until mental status improves significantly.
Evacuation is required for moderate hypothermia if achievable. Field management is a bridge.
Severe Hypothermia (Below 28°C) — Unconscious
Check for a pulse for 60 seconds before beginning CPR. Hypothermia severely slows heart rate — it may be too slow and weak to detect by feel. A pulse of 10-20 beats per minute is not an indication for CPR. Take a full minute before starting compressions.
If no pulse detected after 60 seconds: begin CPR. Hypothermic CPR is exhausting and the outcome uncertain in the field, but must continue until the patient is rewarmed.
Do not defibrillate below 30°C. Ventricular fibrillation in hypothermia often will not convert until the heart is warmer. If an AED is available, follow its prompts but recognize that cardioversion may not succeed until rewarming.
Evacuation is a true emergency. Severe hypothermia requires active core rewarming — warm IV fluids, warm humidified oxygen, or in extreme cases extracorporeal rewarming — that cannot be done in the field.
Cold Water Immersion
Water immersion hypothermia progresses faster than cold air hypothermia by a factor of 5-25 depending on temperature. A person in 10°C water has a survival time measured in hours.
During immersion: Conserve heat by minimizing movement. The Heat Escape Lessening Posture (HELP position) — knees drawn to chest, arms clamped against armpits, head back — reduces heat loss significantly compared to treading water. If multiple people are in the water, huddle together.
On rescue: Horizontal extraction is preferable to vertical. Rescuing someone vertically from cold water can cause sudden cardiac arrest from the hydrostatic pressure change — blood pools in the lower extremities rapidly, causing circulatory collapse.
After extraction from cold water: Begin the rewarming protocol above. Core temperature continues to fall for 30-60 minutes after rescue (afterdrop). The most dangerous period is often after the patient is out of the water, not during immersion.
What Not to Do
Do not rub or massage the extremities. This accelerates afterdrop by returning cold blood to the core rapidly.
Do not give alcohol. It feels warming and is harmful.
Do not let the patient walk to warm up. Exercise moves cold blood from extremities to core rapidly — afterdrop. The hypothermic patient should be moved passively.
Do not rewarm too fast in moderate/severe cases. Rapid rewarming can cause rewarming shock. Core rewarming first, slow and steady.
Do not assume the patient is dead based on appearance. No pulse, fixed and dilated pupils, apparent rigor — these can all be present in profound hypothermia with a viable patient. Rewarm first.
Frostbite — Brief Reference
Frostbite is local tissue freezing, distinct from systemic hypothermia.
Field treatment: Do not rewarm frostbitten tissue if there is any risk of refreezing. A refreezing injury is far worse than the original. Walking on frostbitten feet is preferable to thawing them in the field if the patient must still walk to safety.
When safe to rewarm: Immerse in water at 37-40°C (feels warm to an unaffected hand but not hot) for 20-30 minutes. Expect significant pain as sensation returns — this is normal and is a positive sign of circulation returning.
Do not: rub frostbitten tissue, apply dry heat (fire, heating pad), break blisters, or smoke (vasoconstriction).
Sources
Frequently Asked Questions
When do you stop CPR on a hypothermic patient?
Not until they are rewarmed. 'No one is dead until they are warm and dead.' Hypothermia can produce profound metabolic slowing that mimics death — no apparent pulse, no breathing, pupils fixed and dilated — and patients have survived neurologically intact. Continue CPR and aggressively rewarm. Only cease resuscitation if the core temperature exceeds 32°C after rewarming and the patient remains in cardiac arrest, or if there is clear evidence of death unrelated to hypothermia (non-survivable injuries).
What is afterdrop and how do you prevent it?
Afterdrop is the continued fall in core temperature that occurs after a hypothermic patient is removed from cold exposure, as cold blood from the extremities mixes with warmer core blood. It is most significant during active rewarming of extremities. Prevention: rewarm the core first (trunk, neck, groin, armpits), not the extremities. Limit movement of the hypothermic patient — exercise and limb movement both accelerate afterdrop.
Is it safe to give a hypothermic person alcohol to warm up?
No. Alcohol causes vasodilation — it makes the skin feel warm by shunting blood to the periphery, but this accelerates heat loss from the body surface and lowers core temperature. Alcohol also impairs the shivering response and judgment. It is harmful in hypothermia. Hot sweet drinks (not alcohol) are appropriate for mild, conscious hypothermic patients who can swallow safely.