Practice Guidelines
Accidental Hypothermia: Guidelines from the Wilderness Medical Society
Am Fam Physician. 2020 Nov 1;102(9):571-572.
Author disclosure: No relevant financial affiliations.
Key Points for Practice
• Outside the hospital, hypothermia is diagnosed by presentation, not core temperature. Movement is impaired in mild hypothermia, and alertness lost and shivering slowed or stopped in moderate hypothermia.
• Insulation and vapor barrier from the ground and elements are key to all hypothermia treatment.
• Moderate and severe hypothermia require active warming and gentle handling to prevent dysrhythmia.
From the AFP Editors
Accidental hypothermia occurs when core temperature reaches 95°F (35°C) or lower outside of medical therapy. Hypothermia is common in wilderness environments and among urban homeless, especially with the use of alcohol or other intoxicating substances. Shivering slows around 89.6°F (32°C) and ceases by 86°F (30°C). Brain activity begins to decline around 93.2°F (34°C). Below 86°F, decreased cardiac output and bradycardia predispose the patient to dysrhythmia.
The Wilderness Medical Society has published an updated guideline on treating accidental hypothermia outside of hospitals, including a staging classification system based on clinical observation.
Evaluation
Hypothermia first affects movement when mild, followed by declining alertness and loss of shivering in moderate hypothermia before a person becomes unconscious. Hypothermia should be considered in people who feel cold and are shivering and who are incapacitated or having difficulty caring for themselves. Table 1 shows how presentation changes with each stage of hypothermia. Outside a hospital, the diagnosis of hypothermia and treatment is guided by patient assessment because core temperature readings are difficult and inaccurate.
Hypothermia Stages and Treatment
| Stage | Core temperature* | Signs | Treatment | |||
|---|---|---|---|---|---|---|
|
| ||||||
| Movement | Shivering | Alert | Conscious | |||
Cold stressed, no hypothermia | > 95°F (35°C) | Normal | Yes | Yes | Yes | Reduce heat loss Warmed, high-calorie food or drink Move/exercise |
Mild hypothermia | 95 to 89.6°F (35 to 32°C) | Impaired | Yes | Yes | Yes | Handle gently Insulate/vapor barrier Sit or lie down for 30 minutes Active heating to upper trunk Warmed, high-calorie food or drink Evacuate if no improvement in 30 minutes If improving, move/exercise |
Moderate hypothermia | 89.6 to 82.4°F (32 to 28°C) | Impaired | Slows or stops | No | Yes | Handle gently Keep horizontal No food or drink Insulate/vapor barrier Active heating to upper trunk Volume replacement with warm intravenous fluids Evacuate carefully |
Severe hypothermia | < 82.4°F (28°C) | None | None | No | No | All moderate hypothermia treatments Perform 60-second breathing and pulse check and start cardiopulmonary resuscitation if indicated Evacuate carefully |
*—Core temperature is not useful in the field, and treatment is based on patient presentation.
Hypothermia Stages and Treatment
| Stage | Core temperature* | Signs | Treatment | |||
|---|---|---|---|---|---|---|
|
| ||||||
| Movement | Shivering | Alert | Conscious | |||
Cold stressed, no hypothermia | > 95°F (35°C) | Normal | Yes | Yes | Yes | Reduce heat loss Warmed, high-calorie food or drink Move/exercise |
Mild hypothermia | 95 to 89.6°F (35 to 32°C) | Impaired | Yes | Yes | Yes | Handle gently Insulate/vapor barrier Sit or lie down for 30 minutes Active heating to upper trunk Warmed, high-calorie food or drink Evacuate if no improvement in 30 minutes If improving, move/exercise |
Moderate hypothermia | 89.6 to 82.4°F (32 to 28°C) | Impaired | Slows or stops | No | Yes | Handle gently Keep horizontal No food or drink Insulate/vapor barrier Active heating to upper trunk Volume replacement with warm intravenous fluids Evacuate carefully |
Severe hypothermia | < 82.4°F (28°C) | None | None | No | No | All moderate hypothermia treatments Perform 60-second breathing and pulse check and start cardiopulmonary resuscitation if indicated Evacuate carefully |
*—Core temperature is not useful in the field, and treatment is based on patient presentation.
Treatment
MILD HYPOTHERMIA
In mild hypothermia, shivering can effectively produce heat if patients are insulated from the elements. Protection from further cooling should include using insulation and a vapor barrier, especially for the head and neck and between the patient and the ground. Wet clothes should not be removed until the patient is in a warm environment.
An alert patient with effective shivering and no increased aspiration risk can benefit from warmed, high-calorie liquid or food. The patient should remain seated or horizontal for at least 30 minutes and be carefully observed after that. After a period of warming, calorie replacement, and observation, allowing the patient to increase exercise slowly to generate additional heat may be considered. Active external heat sources should be applied to the axillae, chest, and back. Use of insulation with vapor barriers with active heat sources will maximize heat absorption.
Coverage of guidelines from other organizations does not imply endorsement by AFP or the AAFP.
This series is coordinated by Michael J. Arnold, MD, contributing editor.
A collection of Practice Guidelines published in AFP is available at https://www.aafp.org/afp/practguide.
Copyright © 2020 by the American Academy of Family Physicians.
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