Recommended Methods for Rapid Rewarming in Hypothermia
For hypothermia cases requiring rapid rewarming, patients should be protected from further heat loss by moving to a warm environment, removing saturated clothing, applying passive rewarming with blankets, and implementing active rewarming methods appropriate to the severity of hypothermia. 1
Classification and Treatment Approach Based on Severity
Mild Hypothermia (34-36°C)
- Remove wet clothing immediately and move to a warm environment 1
- Apply passive external rewarming with warm blankets 1, 2
- Provide high-calorie foods or drinks if the patient is alert and can safely consume them 1
- Natural rewarming rate is approximately 1.2°C/hour, which can increase to 3.6°C/hour with shivering 1, 2
Moderate Hypothermia (28-32°C)
- Continue all interventions for mild hypothermia 1, 2
- Implement active external rewarming methods:
- Active external rewarming has been shown to increase core temperature by approximately 0.74°C during transport, while passive rewarming alone may cause a temperature decrease 1
- Forced air rewarming can achieve mean rewarming rates of 1.7°C/hour (range 0.7-3.4°C/hour) 3
Severe Hypothermia (<28°C)
- Continue all interventions for mild and moderate hypothermia 1, 2
- Implement active internal (core) rewarming methods:
- Even in severe hypothermia, external rewarming methods can still be effective, with studies showing successful warming of patients with temperatures below 30°C using forced-air warmers 1, 3
Critical Considerations for All Hypothermia Cases
- If a patient has decreased level of responsiveness (unresponsiveness, inability to remain awake, mumbling speech, confusion), activate emergency response system immediately while initiating rewarming 1
- When using any rewarming device, follow manufacturer's instructions, place insulation between heat source and skin, and monitor frequently for burns 1
- If the patient cannot be moved from a cold environment, protect from further heat loss by:
- For patients wearing damp (not saturated) clothing who cannot be moved to a warm environment, active rewarming through the clothing using chemical heat blankets, plastic/foil layers, and insulative blankets is reasonable 1
- Body-to-body rewarming is not recommended over other active rewarming techniques 1, 4
Rewarming Methods Effectiveness
- Whole-body immersion in water at 42°C shows the highest rewarming rate (10.1°C/hour) with minimal afterdrop (0.18°C) for mild hypothermia in controlled settings 5
- Forced air surface rewarming has been proven effective even in severe hypothermia cases with core temperatures below 30°C 3
- Hand/extremity-only immersion in hot water is ineffective and may potentially be detrimental by suppressing intrinsic heat production 4
- The rewarming target should be a minimum core temperature of 36°C, and rewarming should cease after reaching 37°C as higher temperatures are associated with poor outcomes 2, 6
Pitfalls and Caveats
- Hypothermia is often overlooked during initial resuscitation but can be present in up to two-thirds of patients with severe injury 2, 6
- Clinical presentation may not always match the severity of hypothermia; diagnosis and treatment should be based on core body temperature measurement rather than clinical presentation alone 7
- Emphasis should be on prevention first and treatment second, as it becomes increasingly difficult to rewarm patients once significant heat is lost 1, 2
- Burns from active external rewarming can occur; ensure proper insulation between heat sources and skin, and monitor skin regularly 1
- Early organized prehospital hypothermia protocols have been shown to reduce hypothermia incidence from 19% to 3% 1, 2