The hypothermia wrap (sometimes called “burrito”) is the most important field first-aid technique for hypothermia. Its purpose is not to warm the victim but to stop further heat loss and keep the patient safe until evacuation. A well-built wrap gives the body a chance to recover core temperature on its own. This article covers precise construction, common mistakes, and differences between active and passive warming variants.
Fundamental rules
- Order is fixed: first insulation and loss prevention, only then warming
- Warm only centrally (chest, neck, armpits, groin) — never extremities
- Avoid rough handling — in HT II and below, risk of ventricular fibrillation
- No alcohol — dilates skin vessels, accelerates core cooling
- Nothing by mouth in HT II+ — aspiration risk
Five-layer construction
Layer 1 — ground insulation
Backpack, foam pad, branches, dry leaves — anything that separates the victim from cold or wet ground. Conductive heat loss to the ground is the fastest of all mechanisms. Without this layer the rest of the wrap works at 40–60% efficiency.
Layer 2 — thermal reflective film (NRC) or tarp
NRC silver-gold foil, rain poncho, emergency tarp. Function: reflecting thermal radiation and blocking wind. Inside the wrap it acts as a “vapor barrier” — stops sweat evaporation cooling the skin.
Layer 3 — thermal insulation (sleeping bag, down jacket)
A dry sleeping bag is ideal — preferably down (synthetic works but loses to moisture). Alternative: several down jackets wrapped around the patient. This layer is the thickest and most thermally important. If the victim is in wet clothing — remove it before putting them in the wrap, otherwise wet fabric destroys the down insulation.
Layer 4 — active heat sources (optional)
Chemical warmers (HotHands, Grabber), hot-water bottles, reactive heat packs. Place only centrally: chest (over the heart), armpits, groin, sides of the neck. Never on feet, hands, or legs — afterdrop risk (cold peripheral blood rushing to torso after vasodilation, lowering heart temperature).
Layer 5 — outer shell (tarp, second NRC)
Second waterproof/windproof layer seals the system. Protects from rain, snow, wind. Can be a tarp, bothy bag, large NRC foil.
Practical sequence
- Prepare materials — lay out all layers in order on the ground beside the victim
- Assess condition (Swiss Staging: HT I/II/III/IV), measure SpO₂, check pulse
- Remove wet clothing — if HT I and cooperative, let them undress; if HT II+, carefully cut wet layers with scissors
- Dry the patient (towel, t-shirt), dress in dry thermal layers
- Lay out layer 1 and 2 (ground insulation + foil/tarp)
- Place the patient on layer 2, wrap in layer 3 (sleeping bag or jackets)
- Add layer 4 (heat sources centrally, if available)
- Close with layer 5 (wind- and waterproof outer shell)
- Secure head and neck — hat, scarf, second hood. Head loses up to 30% of body heat
- Monitor every 15 min — pulse, breathing, responsiveness; SpO₂ every 30 min
Common mistakes
Warming extremities
Instinctively we want to put a warmer on cold feet. Mistake. Peripheral extremities hold cold blood — heat-induced vasodilation sends it back to the torso. Heart temperature drops another 1–2°C (afterdrop), raising VF risk.
Hot bath or hot tea
Old “advice” from popular literature. A hot bath is neither available in the field nor safe — same afterdrop mechanism. Warm (not hot) sweet tea is OK, but only for conscious, cooperative HT I patients who can swallow safely.
Rubbing skin and massage
Do not. Mechanical irritation of cold skin can trigger VF. No limb massage, no hand-rubbing, no shaking “to warm them up”.
Fast transport without stabilization
A patient in HT II/III needs gentle horizontal transport. Fireman’s carry, bouncy hand carry, or head-up positioning are stimuli that can trigger VF. If carrying is required — improvised stretcher with full wrap.
Minimalist version — improvising from climbing gear
- 1 NRC foil under patient (layers 1+2)
- 1 dry sleeping bag or 2 down jackets wrapped (layer 3)
- 2–3 chemical warmers centrally (layer 4)
- 1 NRC foil on top + backpack/gore-tex jacket as windshield (layer 5)
Such a “backpack wrap” works surprisingly well in HT I and mild HT II — buys an hour or two, usually enough for rescue to arrive. For HT III/IV think about evacuation to an ECMO center — no field wrap replaces extracorporeal circulation.
Transport to ECMO — a critical decision
In HT III with cardiac arrest or HT IV the target hospital must have ECMO (Extracorporeal Membrane Oxygenation) capability. This information must reach the dispatcher at the moment of the call, not after the team arrives. Transport logistics may require an air ambulance with a dedicated flight path.
A wrap gives the patient a chance at prolonged resuscitation — ECMO allows CPR for hours while rewarming the blood extracorporeally. Rule: nobody is dead until warm and dead.
Frequently asked questions
Why only central warming, not on feet?
Afterdrop mechanism: in hypothermia peripheral blood is cold (vessels constricted). Warming the extremities dilates vessels and cold blood rushes to the torso, dropping heart temperature another 1–2°C. Central warming (chest, neck, armpits, groin) targets large torso vessels without this risk.
Can I give tea to a hypothermic person?
Warm (not hot) sweet tea only in HT I (35–32°C) when the victim is conscious, cooperative, and can swallow safely. Sugar fuels shivering (the largest natural heat generator). In HT II and deeper — nothing by mouth (aspiration risk). Alcohol is absolutely prohibited at any stage.
How long does a chemical warmer last?
A classic HotHands maintains 50–60°C for 8–10 hours. Inside a wrap, muted by insulation, effective duration is 4–6 hours. On expedition carry 4–6 warmers per person in the emergency kit.
Can I use a damp down sleeping bag?
Better than nothing, but far worse than dry. Down loses 60–80% of insulation when wet. If only wet down is available, prefer synthetic or several dry jackets. In emergencies: newspapers, dry leaves, dry grass stuffed between clothing layers act as improvised insulation.
What if the HT II patient stops breathing?
Check pulse for at least 60 seconds (bradycardia in hypothermia can be 20–30/min, easy to miss). If no pulse and no breathing — CPR per ERC/ICAR guidelines: chest compressions 100–120/min, breaths 30:2. Simultaneously active central warming. Rule: nobody is dead until warm and dead — continue CPR until rescue takeover or core temperature at least 32°C in hospital.
References
- Zafren K, Giesbrecht GG, Danzl DF, et al. Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update. Wilderness Environ Med. 2014;25(4):S66–S85.
- Paal P, Pasquier M, Darocha T, et al. Accidental hypothermia: 2021 update. Int J Environ Res Public Health. 2022;19(1):501.
- ICAR MEDCOM field treatment guidelines — alpine-rescue.org.
Disclaimer: This article is informational and does not replace individual medical consultation.