Hypothermia is not just a problem for alpine rescue. In a year-long study at The Alfred in Melbourne, 13.25 per cent of major trauma patients arrived hypothermic, and those patients had a threefold independent risk of death (Ireland et al., Resuscitation). Even in sub-tropical Queensland, hypothermia on arrival at hospital was linked to four times the odds of dying (Aitken et al., Resuscitation).
Injured patients lose heat quickly. Blood loss, exposure during assessment, wet clothing, cold ground, wind, intubation and cold fluids all add up, and a patient who is already bleeding cannot generate enough heat to keep up. Once core temperature falls, clotting gets worse, which feeds more bleeding.
The good news is that heat loss is one of the most preventable problems in trauma care. This guide covers what Australian guidelines recommend, how heat is lost in the field, what the evidence says about foil blankets compared with insulated hypothermia blankets, and how to build a practical hypothermia prevention routine for ambulance, event, workplace, remote and tactical settings.
Key Takeaways
- Hypothermia is common in Australian trauma. A Melbourne study found 13.25 per cent of major trauma patients were hypothermic on arrival, with a threefold independent risk of death.
- It happens in warm climates too. Queensland registry data linked hypothermia on admission to four times the odds of death, with winter, severe injury and hypotension as risk factors.
- ANZCOR recommends insulation plus a vapour barrier. The guideline suggests combining an insulating layer, such as woollen blankets, with a vapour barrier, such as plastic wrap.
- Foil blankets alone have limits. Reviews find little evidence that reflective foils work well as a single layer, especially in wind, although they are useful as a windproof, waterproof outer cover.
- Thicker, windproof insulation performs better. Thermal studies show insulation scales with thickness, and windproof systems keep more of their performance in wind.
- Start early and insulate from the ground. Prevention is far easier than rewarming, so cover the patient as soon as the primary survey allows.
Why Hypothermia Matters in Trauma
The Australian Evidence
Two major Australian studies show the scale of the problem.
| Study | Setting | Key findings |
|---|---|---|
| Ireland et al., 2011 | The Alfred, Melbourne, 732 major trauma patients | 13.25% hypothermic on arrival; 29.9% mortality in hypothermic patients; threefold independent risk of death |
| Aitken et al., 2009 | Queensland Trauma Registry, 2,182 seriously injured patients | 5.7% hypothermic on admission; a further 7.1% became hypothermic in hospital; four times the odds of death if hypothermic on arrival |
In the Melbourne study, the strongest predictors of hypothermia were prehospital intubation, higher injury severity, low blood pressure on arrival and winter. The authors called for a coordinated effort by paramedics, nurses and doctors to resolve hypothermia early, aiming for a temperature above 35°C.
The Queensland authors noted that trauma patients in a "predominantly sub-tropical climate" are still at risk of both accidental and endogenous hypothermia. A warm day does not protect a bleeding, exposed patient lying on cold ground.
Hypothermia and the Triad of Death
Hypothermia is one part of the lethal combination of hypothermia, acidosis and coagulopathy. Cold slows the clotting cascade, so a cold patient bleeds more, and more bleeding leads to more heat loss. Our article on the trauma triad of death explains this cycle in more detail. This guide focuses on the practical part: how to stop the temperature falling in the first place.
How Patients Lose Heat in the Field
Heat is lost in four ways. Each needs a different fix.
| Mechanism | What happens | Field fix |
|---|---|---|
| Conduction | Heat flows into cold ground, stretchers, wet clothing or water | Insulate underneath the patient; remove wet clothing |
| Convection | Wind and moving air strip heat from the skin | Use a windproof outer layer; shelter from wind |
| Evaporation | Wet skin and clothing lose heat as moisture evaporates | Remove wet clothing or add a vapour barrier |
| Radiation | The body radiates heat to cooler surroundings | Cover the patient, including the head; reflective layers help |
Research from Umeå University found that removing wet clothing or adding a vapour barrier cut total heat loss by 19 to 42 per cent, a reduction similar to increasing insulation from one to two blankets (Henriksson, Umeå University). The authors noted this matters most in cold environments where little insulation is available, such as mass casualty incidents or long evacuations.
What Australian Guidelines Recommend
ANZCOR Guideline 9.3.3
The ANZCOR Guideline 9.3.3 on hypothermia and cold-related injuries sets out first aid recommendations used across Australia and New Zealand. Key points include:
- Follow DRSABCD, including CPR and early defibrillation for anyone unresponsive and not breathing normally.
- Move the person to a warm, dry shelter as soon as possible, keep them lying flat and minimise their movement.
- Remove wet clothing, replace it with dry clothing and protect the person from wind and draughts.
- Prevent further heat loss using an insulation layer combined with a vapour barrier.
- Begin active rewarming, such as heat packs applied inside the insulation, following the manufacturer's directions to avoid burns.
Ambulance Clinical Practice Guidelines
Ambulance services build on these principles. The Queensland Ambulance Service hypothermia CPG directs paramedics to place the patient in a warm environment such as a warmed vehicle, remove all wet clothing, insulate with blankets, manage treatable conditions at the same time and monitor temperature continuously. It also warns that hypothermic patients must be moved carefully and gently because they are at higher risk of ventricular fibrillation.
Always follow your own service's clinical practice guidelines and scope of practice.
Foil Blankets: What the Evidence Says
Foil rescue blankets are in almost every first aid kit in Australia. They are light, cheap to stock and take up almost no space. But they are often expected to do more than they can.
Where Foil Blankets Fall Short
A review in Wilderness and Environmental Medicine concluded that while trade names and descriptions suggest these foils have insulating properties, "there is no evidence that they are effective", and the only support comes from theoretical calculations and a few small studies (Kosiński et al.). The review found:
- In still air, a foil can provide protection similar to a woollen blanket.
- Moderate wind reduces protection by up to 40 per cent, and strong wind by up to 55 per cent.
- In moderate or strong wind, the reflective coating adds little, and the foil performs about the same as plain plastic of the same thickness.
- Foils provide little protection from conduction, and they tear easily.
There is another problem specific to hypothermic patients. A survey of Italian helicopter services notes that a severely hypothermic patient radiates very little heat, so there is little energy for a foil to reflect back (Italian HEMS survey).
Where Foil Blankets Help
Foil blankets are not useless. The same review notes they are lightweight, waterproof and windproof, can increase visibility in search and rescue, and work well as part of a multilayer system. One study found that adding a rescue foil inside one or two blankets improved insulation in wind compared with blankets alone.
The practical conclusion is that a foil blanket works best as a windproof, waterproof outer layer or vapour barrier, not as the only layer between a trauma patient and the environment.
Insulated Hypothermia Blankets
Thickness and Wind Resistance Matter
A study of 12 blankets and rescue bags used by prehospital services found that, in low wind, insulation was closely linked to the thickness of the ensemble. In moderate and high wind, windproof systems that resisted compression kept 60 to 80 per cent of their insulation, while wind-permeable or lighter materials fell to 30 to 50 per cent (Henriksson et al., Prehospital and Disaster Medicine).
A manikin study of mountain rescue insulation systems found that heavyweight casualty bags and multilayer systems slowed cooling far more than thin foil or plastic survival bags (Rates of cooling of an insulated manikin).
What TOG Means
Blanket insulation is often rated in TOG (thermal overall grade). The higher the TOG, the more the material resists heat flow. One TOG equals 0.1 m²·K/W, and 1 clo, the unit used in many clothing studies, is about 1.55 TOG. A rating gives a useful way to compare products, but the real-world result also depends on fit, wind, moisture and insulation underneath the patient.
Comparing Foil and Insulated Blankets
| Feature | Foil emergency blanket | Insulated hypothermia blanket |
|---|---|---|
| Main role | Wind and water barrier, vapour barrier, radiant reflection | Primary insulation for prolonged exposure |
| Performance in wind | Drops significantly when used alone | Windproof designs keep more of their insulation |
| Protection from conduction | Little | Better, especially with ground insulation |
| Durability | Tears easily; single use | Tear-resistant and reusable |
| Weight and pack size | Very light and small | Larger and heavier |
| Best fit | First aid kits, IFAKs, vehicles, mass casualty stock | Ambulances, rescue teams, remote and tactical kits, events in cold or wet conditions |
Most services and responders need both. Foil blankets give every kit a basic barrier, while insulated blankets provide real protection when a patient is exposed for longer, wet or in wind.
A Practical Hypothermia Prevention Routine
The Layered Wrap
International guidance often describes a layered "burrito" or Hibler-style wrap. Adapted for field use:
- Insulate from the ground first. Place a blanket, mat or other insulation under the patient before or during the move.
- Remove wet clothing once the patient is sheltered from wind, preferably by cutting it off to minimise movement.
- Add a vapour barrier if the patient is wet and clothing cannot be removed. A foil blanket or plastic sheet works well here.
- Wrap with insulation. Cover the whole body, including the head and neck, leaving only the face exposed.
- Add a windproof, waterproof outer layer if the insulation is not already windproof.
- Apply active warming if available, such as heat packs to the armpits, chest or back inside the insulation, following manufacturer directions and your service's guidelines.
- Keep the patient flat and handle gently, especially if hypothermia is moderate to severe.
Exposure Without Cooling
A full primary survey still requires exposure. The aim is to expose only what you need, then cover again straight away. Assess under a blanket where possible, and re-cover each area after you have examined it.
High-Risk Patients
Pay particular attention to:
- Patients who are bleeding, hypotensive or severely injured
- Intubated and sedated patients, who cannot shiver
- Older adults and children, who lose heat faster
- People pulled from water or found wet
- Prolonged entrapment, extrication or remote evacuation
- Burns patients, who lose heat through damaged skin
- People affected by alcohol or drugs
Settings Where Hypothermia Is Easy to Miss
Australia's climate leads many responders to underestimate cold. Common risk scenarios include:
- Night-time road trauma and rural crashes with long extrication times
- Marine, surf and inland water rescues
- Alpine and high-country areas in Tasmania, Victoria and New South Wales
- Outdoor events, trail races and endurance sports in wind or rain
- Mine sites, construction sites and remote workplaces
- Disasters and mass casualty incidents with limited shelter
For trauma kits, our IFAK configuration guide covers how to set up an individual first aid kit, including space for a foil blanket.
Frequently Asked Questions
How common is hypothermia in Australian trauma patients?
A prospective study at The Alfred in Melbourne found 13.25 per cent of major trauma patients were hypothermic on arrival. Queensland registry data found 5.7 per cent were hypothermic on admission, with a further 7.1 per cent becoming hypothermic in hospital.
Why is hypothermia dangerous after trauma?
Hypothermia worsens blood clotting, which increases bleeding and further heat loss. Australian studies found hypothermic trauma patients had three to four times the odds of dying, independent of other measured risk factors.
Do foil emergency blankets work?
They help, but they have limits. Foil blankets can match a woollen blanket in still air, but their protection drops by up to 40 to 55 per cent in wind and they offer little protection from cold ground. They work best as a windproof, waterproof outer layer or vapour barrier combined with insulation.
What does ANZCOR recommend to prevent heat loss?
ANZCOR Guideline 9.3.3 suggests combining an insulation layer, such as woollen blankets, with a vapour barrier, such as plastic wrap, after moving the person to shelter and removing wet clothing.
What is a TOG rating on a hypothermia blanket?
TOG measures how well a material resists heat flow. A higher TOG means more insulation. One TOG equals 0.1 m²·K/W, and 1 clo, a unit used in many studies, is about 1.55 TOG.
Should I remove a trauma patient's wet clothing?
Yes, once they are sheltered from wind and cold. Removing wet clothing or adding a vapour barrier cut total heat loss by 19 to 42 per cent in thermal studies. If you have no dry cover available, add a vapour barrier first rather than leaving the patient exposed.
Can hypothermia happen in summer in Australia?
Yes. Injured patients can become hypothermic in mild weather because of blood loss, exposure, wet clothing, cold ground and wind. Queensland data shows hypothermia occurs in trauma patients even in a predominantly sub-tropical climate.
When should I start hypothermia prevention?
As early as possible. Control life-threatening bleeding first, then insulate the patient from the ground and cover them as soon as the primary survey allows. Prevention is far easier than rewarming.
Build Hypothermia Prevention Into Every Kit
Heat loss starts the moment a patient is injured. MyMedEquip stocks reusable hypothermia blankets and foil emergency blankets so you can match your thermal protection to your setting, from first aid kits to ambulances and remote response packs.
→ Igloo Pro 3-Layer Hypothermia Blanket (Emergency Orange) – a reusable 7 TOG, 2.3 m × 1.8 m blanket with a tear-resistant, waterproof and windproof outer shell, in high-visibility orange
→ Igloo Pro Hypothermia Blanket (Coyote Brown) – the same 7 TOG design in a low-visibility colour for tactical and field use
→ AeroRescue Emergency Thermal Blankets – lightweight foil blankets for first aid kits, vehicles and mass casualty stock, available in multi-packs
Author: Theodore Dimitriou
This article is general information only. It does not replace your service's clinical practice guidelines, first aid training or scope of practice.
Sources
- Ireland et al. – The Incidence and Significance of Accidental Hypothermia in Major Trauma, Resuscitation
- Aitken et al. – Hypothermia and Associated Outcomes in Seriously Injured Trauma Patients in a Predominantly Sub-tropical Climate, Resuscitation
- ANZCOR – Guideline 9.3.3 First Aid Management of Hypothermia and Cold-Related Injuries
- Queensland Ambulance Service – Clinical Practice Guideline: Hypothermia
- Kosiński et al. – Prehospital Use of Ultrathin Reflective Foils, Wilderness and Environmental Medicine
- Henriksson et al. – Protection Against Cold in Prehospital Trauma Care, Umeå University
- Henriksson et al. – Evaporative Heat Loss Reduction by Wet Clothing Removal or a Vapour Barrier
- Measurements of Rates of Cooling of a Manikin Insulated With Rescue Systems
- Prehospital Management of Accidental Hypothermia: A Nationwide Survey of Italian HEMS