Treating Hypothermia in the Field — Stages and Rewarming Protocol

Hypothermia kills more people in the backcountry than almost any other cause — and it kills in deceptively warm temperatures (40-50°F) when combined with wet clothing, wind, and exhaustion. The deaths are almost always preventable if someone catches the early stages.

Recognition is everything. Hypothermia progresses through three stages: MILD (95-89°F core), MODERATE (89-82°F), and SEVERE (below 82°F). Each stage has different treatment and different risk levels. Treat the early stages aggressively and you save lives. Miss the early stages and you have a rapidly dying patient.

Stage recognition

• ☐ MILD (95-89°F): Intense shivering, fumbling hands, slurred speech, "umbles" (stumbles, mumbles, fumbles, grumbles), irritable or withdrawn behavior
• ☐ MILD: Patient is still conscious and can help with their own treatment
• ☐ MODERATE (89-82°F): Shivering stops or becomes intermittent (CRITICAL warning sign), confusion, pale or blue skin, slow pulse, irrational behavior
• ☐ MODERATE: Patient is barely conscious, cannot self-treat, may attempt "paradoxical undressing" (removing clothes due to false warmth sensation)
• ☐ SEVERE (below 82°F): No shivering, loss of consciousness, extremely slow or irregular pulse and breathing, may appear dead
• ☐ SEVERE: Patient is unconscious and actively dying — needs hospital-level care immediately
• ☐ AT ANY STAGE: Wet clothes + wind exposure can drop core temperature 1°F per 3 minutes
• ☐ NEVER assume someone is dead from hypothermia without professional assessment ("you're not dead until you're warm and dead")

Mild hypothermia is fully recoverable in the field if you catch it early. The goal is simple: stop heat loss, add heat. Get them out of wet clothes, into insulation, into shelter, and feed them calories. A mildly hypothermic patient will warm up on their own if you control the environment.

Avoid the temptation to rush. Gradual rewarming is safer than aggressive rewarming. Do NOT massage cold limbs (pushes cold blood back toward the heart, causes arrhythmia). Do NOT give alcohol (vasodilates, increases heat loss). Do NOT immerse in hot water (rewarming shock).

Mild hypothermia protocol

• ☐ Get them out of wind and rain immediately — shelter first, everything second
• ☐ Remove ALL wet clothing (cut it off if removing is hard — do not waste time)
• ☐ Insulate from the ground (pad, pack, pine boughs — ground steals heat fast)
• ☐ Wrap in dry insulating layers (sleeping bag, emergency bivvy, mylar blanket, dry clothing)  → Buy
• ☐ Add head and neck insulation (40% of heat loss)
• ☐ Feed them high-calorie foods they can chew easily (candy bars, nuts, chocolate)
• ☐ Give warm (NOT hot) sweet drinks if alert — sugar + warmth
• ☐ Use hand warmers in armpits, groin, neck (major artery points)  → Buy
• ☐ Body-to-body warming inside a sleeping bag if hand warmers unavailable
• ☐ Monitor: shivering should continue and then gradually fade as core temp normalizes

Moderate and severe hypothermia are medical emergencies that cannot be fully treated in the field. Your job is to prevent further heat loss, provide gentle rewarming, and transport to a hospital. The mortality rate for severe hypothermia in the field is high — but zero if you stop trying.

The most dangerous moment in severe hypothermia is rewarming shock (afterdrop). Rewarming cold limbs first pushes icy blood back into the core — dropping core temperature even further and causing cardiac arrest. Always rewarm the CORE (trunk) first, not the extremities. This is why you never put a severely hypothermic patient in a hot tub or shower.

Moderate/severe protocol

• ☐ Call for professional help IMMEDIATELY — this is a 911 emergency
• ☐ Handle the patient GENTLY — rough handling can trigger cardiac arrhythmia in severe cases
• ☐ Do NOT rub or massage limbs — pushes cold blood to the core, causing afterdrop
• ☐ Do NOT immerse in hot water — same cardiac risk, plus burns they cannot feel
• ☐ Do NOT give alcohol — vasodilation increases heat loss
• ☐ Do NOT give food or drink to unconscious patients (aspiration risk)
• ☐ Rewarm the CORE (trunk, neck, armpits, groin) with warm-water bottles or chemical heat
• ☐ Use the burrito method with maximum insulation
• ☐ If unconscious and no breathing: CPR at same compression rate but slower breath intervals
• ☐ "Not dead until warm and dead" — hypothermia can mimic death; rewarming may restore pulse

Every hypothermia case in the field is preventable. The rules are simple: stay dry, stay insulated, stay fueled, stay sheltered. If you are wet, fix it immediately. If you are cold, do not "tough it out" — eat, layer up, move, find shelter. Waiting until you are severely cold is how people die.

The "umbles" (stumbles, mumbles, fumbles, grumbles) are your early warning system. When you or a partner start making mental mistakes, struggling with simple tasks, or becoming irritable for no reason — you are already in early hypothermia. Act on it immediately, not in 20 minutes when you finish the trail.

Prevention rules

• ☐ COTTON KILLS — cotton clothing wet against your skin is a refrigerator. Wear wool, polyester, or nylon base layers.
• ☐ Layer system: base layer (wicks sweat) + insulating layer (traps heat) + shell (blocks wind/water)
• ☐ Always carry extra dry clothes in a waterproof bag, even for day hikes
• ☐ Eat every 2-3 hours in the cold — your body burns 2-3x more calories to maintain core temperature
• ☐ Stay hydrated — dehydration reduces cold tolerance
• ☐ Use the "buddy check" — partners watch each other for the umbles (stumbles, mumbles, fumbles, grumbles)
• ☐ Stop and rewarm BEFORE shivering becomes intense — warning sign, not a badge
• ☐ Never exercise in wet cotton — it transfers body heat away faster than still air
• ☐ In emergencies, the best shelter is whatever breaks the wind (car, lean-to, tarp, even a snow cave)
• ☐ Keep a small emergency bivvy in any pack, any vehicle, any winter kit  → Buy

A dedicated cold-weather emergency kit lives in every winter vehicle, every winter go-bag, and every winter day-hike pack. It does not need to be large — the essentials fit in a gallon ziploc.

Cold-weather kit essentials

• ☐ SOL Emergency Bivvy — reflects 70% of body heat, weighs ounces  → Buy
• ☐ Wool or synthetic base layer change (packed in dry bag)
• ☐ Insulated jacket (down or synthetic) — compressible and packable
• ☐ Wool or synthetic beanie + insulated gloves
• ☐ Hand warmers (12+ packets)  → Buy
• ☐ Closed-cell foam pad for ground insulation  → Buy
• ☐ High-calorie food bars (at least 2,000 cal total)
• ☐ Thermos for hot drinks (if available) or insulated mug
• ☐ Firestarter (ferro rod + stormproof matches + tinder) for emergency fire  → Buy
• ☐ NOAA weather radio for alerts  → Buy
• ☐ Garbage bags for emergency ground insulation or wind barrier
• ☐ First aid kit with chemical body warmers and trauma basics