Accidental hypothermia

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

ACUTE

mild hypothermia: >90°F to 95°F (>32°C to 35°C)

1st line – passive external rewarming

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1st line –

passive external rewarming

Reduce further evaporative heat loss through removal of wet clothing and insulating the patient (e.g., with warm blankets and dry clothes).[45][48][55] Patients should also be given high-calorie food and warm sweet drinks if alert and able to safely consume food and fluids orally; these do not rewarm the patient but will supply energy for shivering.[19][55] Active movement (e.g., standing, walking) should also be encouraged if possible in patients with shivering who have had adequate time to rewarm.[19][48]

Monitor core temperature. Heat redistribution within the body can cause a continued fall in core temperature after removing the patient from a cold environment (also known as afterdrop).

Avoid hyperthermia during and after rewarming.[19]

Consider – supportive care

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Consider –

supportive care

Treatment recommended for SOME patients in selected patient group

Mild hypothermia can usually be managed in a prehospital setting, but patients will require transfer to hospital if they are injured, present with altered consciousness, or are not shivering.

If the patient cannot maintain or protect the airway, it should be secured with an advanced airway (e.g., tracheal tube or supraglottic airway device). Advanced airway placement should be attempted only by those with appropriate training and experience.[20][45] Patients with an advanced airway should be ventilated at half the standard normothermic rate.[48]

Placement of an endotracheal tube may be more difficult in cold environments due to hypothermia-induced trismus.[19][48] If laryngoscopy is not possible, fiber-optic intubation or cricothyroidotomy can help facilitate placement of an endotracheal tube, but it may be preferable to consider a supraglottic airway device until the patient is moved to a warm environment.[48] Be aware that endotracheal intubation may cause ventricular fibrillation (VF) in severe hypothermia. However, this risk is small and the benefits of intubation when indicated outweigh the risk of VF.[19][48]

Manage cardiac arrhythmias as appropriate. All arrhythmias apart from VF (particularly atrial arrhythmias) are likely to improve without treatment as the patient’s core temperature increases.[19][20][48] However, if the patient has bradycardia and hypotension that is disproportionate to their hypothermia, consider transcutaneous pacing.[48]

Treat hypoglycemic patients with dextrose.[48] Hypoglycemia can stop shivering (because the central control of shivering is dependent on glucose), leading to subsequent heat loss.[53] Where blood glucose testing is not available and hypothermic patients present with an altered level of consciousness, empiric dextrose should still be initiated.[48] Monitor blood glucose even after the patient is normoglycemic as rebound hypoglycemia may develop when normal insulin production resumes.

Insulin should not initially be started in patients with hyperglycemia as high blood glucose has not been shown to be detrimental in patients with hypothermia.[48] Seek expert advice if: hyperglycemia is worsening; there is associated ketosis; hyperglycemia persists after successful rewarming; or the patient has type 1 diabetes.

Monitor core temperature and vital signs, including pulse rate, blood pressure, respiratory rate, oxygen saturations, blood gases (to ensure resolution of hypoxia and normalization of pH), and end-tidal CO₂ if the patient is intubated.

Monitor potassium: hypokalemia may occur as a result of hypothermia or the associated treatment and hyperkalemia may occur during rewarming.

Consider – heated humidified oxygen

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Consider –

heated humidified oxygen

Treatment recommended for SOME patients in selected patient group

Heated humidified oxygen therapy can be given regardless of oxygen saturations.[48] This reduces heat loss through respiration, but is not effective as a rewarming method on its own; it should be used as an adjunct to other rewarming techniques.

inadequate response to passive external rewarming

Consider – active external rewarming

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Consider –

active external rewarming

Treatment recommended for SOME patients in selected patient group

Should be initiated if there is an insufficient response to passive methods.

Active external rewarming may involve using electric heat pads or blankets, hot water bottles, chemical heat pads, or forced air warming.[48]

Monitor core temperature. Heat redistribution within the body can cause a continued fall in core temperature after removing the patient from a cold environment (also known as afterdrop).

Avoid hyperthermia during and after rewarming.[19]

Consider – warmed intravenous fluids

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Consider –

warmed intravenous fluids

Treatment recommended for SOME patients in selected patient group

Consider warmed intravenous fluids, especially once rewarming measures have been started. This should be with normal saline, warmed to 104°F to 107.6°F (40°C to 42°C).[48] Warmed intravenous fluids help to prevent heat loss but do not actively rewarm the patient. Infusing warmed intravenous fluid also offers the additional advantage of improved absorption of administered drugs. Lactated Ringer solution should be avoided as the liver will not be able to metabolize lactate in hypothermia.[48]

Circulatory access via a peripheral intravenous catheter is the preferred method, though this may be difficult to achieve in hypothermic patients because of cold-induced peripheral vasoconstriction.[48] If not immediately possible, intraosseous access should be established instead.

It is important that patients are carefully monitored for signs of fluid overload and volume depletion. Large volumes of fluid may be required because vasodilation during rewarming causes expansion of the intravascular space and subsequent hypotension.[19][48] Warmed intravenous fluids should ideally be administered via boluses, guided by vital signs (heart rate and blood pressure) as opposed to continuous infusion, as this will help avoid issues with fluid cooling or lines freezing.[19][48]

moderate or severe hypothermia not in cardiac arrest: ≤90°F (≤32°C)

1st line – supportive care

Back

1st line –

supportive care

Move the patient very carefully and keep them in a supine position. This is crucial as movement can precipitate ventricular fibrillation (VF), especially if the patient’s temperature is <82.4°F (<28°C).[20][48]

Placement of an endotracheal tube may be more difficult in cold environments due to hypothermia-induced trismus.[19][48] If laryngoscopy is not possible, fiber-optic intubation or cricothyroidotomy can help facilitate placement of an endotracheal tube, but it may be preferable to consider a supraglottic airway device until the patient is moved to a warm environment.[48] Be aware that endotracheal intubation may cause VF in severe hypothermia. However, this risk is small and the benefits of intubation when indicated outweigh the risk of VF.[19][48]

Vasoactive drugs are generally avoided when managing hypotension in a patient with significant hypothermia, unless the hypotension is due to other causes (e.g., sepsis) or in highly specialist scenarios (e.g., if the patient is undergoing extracorporeal life support [ECLS]).[20] Always seek urgent advice from the critical care team before giving vasoactive drugs. If indicated, vasoactive drugs should be withheld until the patient’s core temperature is at least ≥86°F (≥30°C).[48] However, the American Heart Association advises that epinephrine (adrenaline) administration is reasonable in cardiac arrest as part of the advanced cardiovascular life support (ACLS) algorithm.[45]

Monitor potassium: hypokalemia may occur as a result of hypothermia or the associated treatment and hyperkalemia may occur during rewarming.

Plus – passive external rewarming

Back

Plus –

passive external rewarming

Treatment recommended for ALL patients in selected patient group

Reduce further evaporative heat loss through removal of wet clothing and insulating the patient (e.g., with warm blankets and dry clothes).[45][48][55]

Monitor core temperature. Heat redistribution within the body can cause a continued fall in core temperature after removing the patient from a cold environment (also known as afterdrop).

Avoid hyperthermia during and after rewarming.[19]

Plus – warmed intravenous fluids

Back

Plus –

warmed intravenous fluids

Treatment recommended for ALL patients in selected patient group

Give warmed intravenous fluids, especially once rewarming measures have been started. This should be with normal saline, warmed to 104°F to 107.6°F (40°C to 42°C).[48] Warmed intravenous fluids help to prevent heat loss but do not actively rewarm the patient. Infusing warmed intravenous fluid also offers the additional advantage of improved absorption of administered drugs. Lactated Ringer solution should be avoided as the liver will not be able to metabolize lactate in hypothermia.[48]

It is important that patients are carefully monitored for signs of fluid overload and volume depletion. It is likely that large volumes of fluid will be required because vasodilation during rewarming causes expansion of the intravascular space and subsequent hypotension.[19][48] Warmed intravenous fluids should ideally be administered via boluses, guided by vital signs (heart rate and blood pressure) as opposed to continuous infusion, as this will help avoid issues with fluid cooling or lines freezing.[19][48]

Plus – active external rewarming

Back

Plus –

active external rewarming

Treatment recommended for ALL patients in selected patient group

Active external rewarming may involve using electric heat pads or blankets, hot water bottles, chemical heat pads, or forced air warming.[48]

It is critical that patients with moderate or severe hypothermia have their core temperature and hemodynamic status continuously monitored during rewarming.[48] Heat redistribution within the body can cause a continued fall in core temperature after removing the patient from a cold environment (also known as afterdrop).

Avoid hyperthermia during and after rewarming.[19]

Plus – active internal rewarming

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Plus –

active internal rewarming

Treatment recommended for ALL patients in selected patient group

Active internal (also known as active core) rewarming, used alone or in combination with active external rewarming, is the most aggressive strategy and is indicated in moderate to severe hypothermia. Active internal rewarming methods include: lavage with warmed normal saline, extracorporeal life support (ECLS), veno-venous rewarming, continuous renal replacement therapy (CRRT), and hemodialysis.[19]

ECLS rewarming provides sufficient circulation and oxygenation while the core body temperature is increased at a rewarming rate of 39.2°F to 50°F per hour (4°C to 10°C per hour).[19] Patients with severe hypothermia, hemodynamic instability, or witnessed out-of-hospital cardiac arrest and those at risk of imminent cardiac arrest should be transferred to centers capable of providing ECLS.[20][48] Patients are at risk of imminent cardiac arrest if they have any of the following: core temperature <86°F (<30°C), or <89.6°F (<32°C) if the patient is frail with multiple comorbidities; ventricular arrhythmia; systolic blood pressure <90 mmHg.

For patients with hemodynamic instability, ECLS rewarming should be considered as it may provide some benefit.[48] Evidence suggests that ECLS rewarming offers a better survival outcome than other treatment modalities.[19][57][58] Preferably, ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO) over cardiopulmonary bypass (CPB).[48]

Patients with severe trauma should be treated aggressively with active rewarming, regardless of the severity of their hypothermia; hypothermia is associated with higher mortality among trauma patients.[3][26][48]

Other methods of active internal rewarming (lavage, veno-venous rewarming, CRRT, and hemodialysis) are less effective and may only be recommended where ECLS rewarming is unavailable.[19]

Irrigation with normal saline (lavage) can be peritoneal, thoracic, gastric, bladder, or colonic, warmed to 104°F to 107.6°F (40°C to 42°C).[19][48]

Avoid hyperthermia during and after rewarming.[19]

Plus – heated humidified oxygen

Back

Plus –

heated humidified oxygen

Treatment recommended for ALL patients in selected patient group

Patients with hypothermia should receive heated humidified oxygen therapy, regardless of their oxygen saturations.[48] This reduces heat loss through respiration, but is not effective as a rewarming method on its own; it should be used as an adjunct to other rewarming techniques.

Consider – hemofiltration

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Consider –

hemofiltration

Treatment recommended for SOME patients in selected patient group

Continuous veno-venous hemofiltration (CVVH), a type of continuous renal replacement therapy, may be considered in patients with hyperkalemia (e.g., due to rewarming or rhabdomyolysis) or acidosis.[61] CVVH is also a form of active internal/core rewarming.[19]

moderate or severe hypothermia in cardiac arrest: ≤90°F (≤32°C)

1st line – cardiopulmonary resuscitation (CPR) ± advanced cardiovascular life support

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1st line –

cardiopulmonary resuscitation (CPR) ± advanced cardiovascular life support

CPR should be initiated promptly and without interruption in patients where vital signs cannot be detected after 1 minute and in patients with a nonperfusing rhythm (including ventricular fibrillation [VF], ventricular tachycardia [VT], and asystole).[20][48] Where possible, ECG monitoring, end-tidal CO₂, and ultrasound should also be used to detect cardiac arrest.[20][48]

Be aware that vital signs may be very difficult to detect in a patient with hypothermia, especially in the prehospital setting; a very hypothermic patient may appear dead but still survive with resuscitation.[20][45][48][49] Do not declare a patient dead prior to full resuscitative measures and aggressive rewarming, unless in the case of nonsurvivable traumatic injury or rigor mortis.[45]

The American Heart Association (AHA) recommends providing standard basic life support (BLS) and advanced cardiovascular life support (ACLS) treatment for patients with accidental hypothermia, combined with the appropriate rewarming techniques in line with the patient's clinical status.[45] In some cases, patients may be unresponsive to cardiovascular drugs, pacemaker stimulation, and defibrillation, although there is an absence of robust data to support this; defibrillation should still therefore be attempted for VF and VT.[45] If defibrillation fails to restore a normal heart rhythm after a single shock, continue adhering to standard BLS and ACLS protocol; there is uncertain evidence regarding the effectiveness of deferring defibrillation until a target core temperature is achieved.[45]

Vasoactive drugs should generally be avoided until patients have been rewarmed to at least 86°F (30°C).[48] This is because drug metabolism and protein binding are both affected in hypothermia so drugs that are administered in patients with very low core temperatures may reach toxic levels with rewarming. However, the AHA advises that epinephrine administration is reasonable in cardiac arrest as part of the ACLS algorithm.[45]

For a patient in cardiac arrest, hyperkalemia can indicate that hypoxia preceded hypothermia (e.g., if the patient was found in an avalanche).[19] Severe hyperkalemia and very low initial core temperatures may predict unsuccessful resuscitation efforts; serum potassium is part of the HOPE (Hypothermia Outcome Prediction after ECLS rewarming for hypothermic arrested patients) score for prognostication of successful rewarming.[20][45][48] [ Hypothermia outcome prediction after ECLS (HOPE) score Opens in new window ] The Wilderness Medical Society states an initial serum potassium >12 mEq/L (>12 mmol/L) is associated with irreversible death if the patient is in cardiac arrest.[48]

See Cardiac arrest.

Plus – supportive care

Back

Plus –

supportive care

Treatment recommended for ALL patients in selected patient group

Placement of an endotracheal tube may be more difficult in cold environments due to hypothermia-induced trismus.[19][48] If laryngoscopy is not possible, fiber-optic intubation or cricothyroidotomy can help facilitate placement of an endotracheal tube, but it may be preferable to consider a supraglottic airway device until the patient is moved to a warm environment.[48] Be aware that endotracheal intubation may cause VF in severe hypothermia. However, this risk is small and the benefits of intubation when indicated outweigh the risk of VF.[19][48]

Monitor potassium: hypokalemia may occur as a result of hypothermia or the associated treatment and hyperkalemia may occur during rewarming.

Plus – passive external rewarming

Back

Plus –

passive external rewarming

Treatment recommended for ALL patients in selected patient group

Reduce further evaporative heat loss through removal of wet clothing and insulating the patient (e.g., with warm blankets and dry clothes).[45][48][55]

Monitor core temperature. Heat redistribution within the body can cause a continued fall in core temperature after removing the patient from a cold environment (also known as afterdrop).

Avoid hyperthermia during and after rewarming.[19]

Plus – heated humidified oxygen

Back

Plus –

heated humidified oxygen

Treatment recommended for ALL patients in selected patient group

Plus – active external rewarming

Back

Plus –

active external rewarming

Treatment recommended for ALL patients in selected patient group

Active external rewarming may involve using electric heat pads or blankets, hot water bottles, chemical heat pads, or forced air warming.[48]

Avoid hyperthermia during and after rewarming.[19]

Plus – warmed intravenous fluids

Back

Plus –

warmed intravenous fluids

Treatment recommended for ALL patients in selected patient group

Plus – extracorporeal life support (ECLS) rewarming

Back

Plus –

extracorporeal life support (ECLS) rewarming

Treatment recommended for ALL patients in selected patient group

For patients with severe hypothermia (core temperature ≤86°F [≤30°C]) and cardiac arrest, extracorporeal rewarming is the preferred method as it allows for rapid rewarming.[19][20][45][48][49] Patients with severe hypothermia, hemodynamic instability, or witnessed out-of-hospital cardiac arrest and those at risk of imminent cardiac arrest should be transferred to centers capable of providing ECLS.[20][45][48] Patients are at risk of imminent cardiac arrest if they have any of the following: core temperature <86°F (<30°C), or <89.6°F (<32°C) if the patient is frail with multiple comorbidities; ventricular arrhythmia; systolic blood pressure <90 mmHg.[20]

ECLS rewarming provides sufficient circulation and oxygenation while the core body temperature is increased at a rewarming rate of 39.2°F to 50°F (4°C to 10°C) per hour.[19] Preferably, ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO) over cardiopulmonary bypass (CPB).[48]

Other methods of active internal rewarming (lavage, veno-venous rewarming, continuous renal replacement therapy [CRRT], and hemodialysis) are less effective and may only be recommended where ECLS rewarming is unavailable.[19] Irrigation with normal saline (lavage) can be peritoneal, thoracic, gastric, bladder, or colonic, warmed to 104°F to 107.6°F (40°C to 42°C).[19][48]

Avoid hyperthermia during and after rewarming.[19]

Consider – hemofiltration

Back

Consider –

hemofiltration

Treatment recommended for SOME patients in selected patient group

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Accidental hypothermia

Treatment algorithm

mild hypothermia: >90°F to 95°F (>32°C to 35°C)

passive external rewarming

supportive care

heated humidified oxygen

active external rewarming

warmed intravenous fluids

moderate or severe hypothermia not in cardiac arrest: ≤90°F (≤32°C)

supportive care

passive external rewarming

warmed intravenous fluids

active external rewarming

active internal rewarming

heated humidified oxygen

hemofiltration

moderate or severe hypothermia in cardiac arrest: ≤90°F (≤32°C)

cardiopulmonary resuscitation (CPR) ± advanced cardiovascular life support

supportive care

passive external rewarming

heated humidified oxygen

active external rewarming

warmed intravenous fluids

extracorporeal life support (ECLS) rewarming

hemofiltration