Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia

Publication Date: December 1, 2019
Last Updated: March 14, 2022

Recommendations

FIELD ASSESSMENT

Factors to guide treatment

The key factors guiding hypothermia treatment are level of consciousness, alertness, shivering intensity, physical performance, and cardiovascular stability, which is based on blood pressure and cardiac rhythm. Core temperature can provide additional helpful information, but it is difficult to accurately obtain in the field, and the panel recommends that this should not be the sole basis for treatment. (1 – Strong, C)
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Simplified decision aid for field use

Cold Card - Front
Cold Card - Back
It is the recommendation of the working group that this decision aid be considered to facilitate evaluation and treatment of accidental hypothermia in the out-of-hospital setting for responders with varying levels of medical training. (G-U, U)
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Some patients are cold, but not hypothermic

It is the recommendation of the panel that a patient who is shivering but able to function well and care for him- or herself be closely observed because this patient is unlikely to be hypothermic. A patient who is shivering, becoming incapacitated, and having difficulty caring for him- or herself is likely to be hypothermic. If there is any doubt, assume that the patient is hypothermic and treat accordingly. (G-U, U)
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Alternate classification of hypothermia

The panel recommends that the American Heart Association (AHA) scheme should not be used as the standard classification for out-of-hospital treatment of hypothermia because it changes the widely accepted definition of hypothermia and emphasizes response to defibrillation rather than physiologic changes. (G-U, U)
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Rescuers should classify hypothermia as mild, moderate, severe, and profound on the basis of clinical observations, remembering that shivering can occur below 32°C, usually with altered mental status, and that patients can have detectable vital signs with core temperatures below 24°C. Furthermore, rescuers should be aware of core temperature overlap between classification categories. (1 – Strong, C)
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Associated conditions complicating the field classification of hypothermia

Clinicians should consider causes other than hypothermia to explain altered mental status or lack of shivering that do not correlate with the measured core temperature or are associated with a history of minimal cold exposure. (1 – Strong, B)
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MEASUREMENT OF CORE TEMPERATURE

Esophageal temperature

If available, an esophageal temperature probe should be placed in a patient whose airway has been protected and secured. Esophageal temperature is the preferred method of core temperature measurement. (1 – Strong, C)
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Epitympanic temperature

Use an epitympanic thermometer designed for field conditions with an isolating ear cap in a patient whose airway has not been secured by endotracheal intubation or a supraglottic airway, or in a patient with a secured airway if an esophageal probe is not available. (1 – Strong, C)
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Infrared tympanic thermometers should never be used to measure core temperature in a hypothermic patient. (1 – Strong, A)
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Rectal temperature in the field

Rectal temperature measurement should not be used unless the patient is in a warm environment. (1 – Strong, C)
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Rectal and bladder temperatures during rewarming

Monitor rectal or bladder temperature during rewarming of an unconscious patient only if an esophageal or epitympanic probe is not available. If rectal or bladder temperature is used for monitoring during rewarming, allow for inaccuracy due to the time lag behind core temperature changes. (1 – Strong, A)
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Oral temperature

Oral temperature measurement with a thermometer that cannot read below 35°C should not be used to diagnose hypothermia. (1 – Strong, A)
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Temporal artery thermometer

Do not use a temporal artery thermometer in a possibly hypothermic patient. (1 – Strong, C)
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Zero-heat flux thermometer

Because this technology has not been validated in field settings, no recommendation can be made at this time. (, U)
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OUT-OF-HOSPITAL TREATMENT

The decision to rescue or resuscitate a patient can only be made after the scene is secure and safe for the rescuers to enter and make an evaluation. (1 – Strong, A)
After rescuer safety has been assured, the priorities for out-of-hospital treatment of a hypothermic patient who is not in cardiac arrest are to avoid causing cardiovascular collapse during rescue, prevent further decrease in core temperature (afterdrop), and rewarm the patient in a safe manner. If a hypothermic patient is in cardiac arrest, rescuers should, if indicated, initiate resuscitation.
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Core temperature afterdrop

Rescuers should keep a hypothermic patient horizontal, especially during rescue from water or a crevasse (1 – Strong, B)
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and should limit physical effort by the patient during rescue. (1 – Strong, B)
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A conscious patient should be encouraged to be attentive and focus on survival. (1 – Strong, C)
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Gentle handling to prevent ventricular fibrillation

Handle a hypothermic patient gently and continue to keep the patient horizontal. (1 – Strong, B)
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Avoid any disturbance, especially movement of the extremities that might precipitate VF. (1 – Strong, B)
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In an effort to minimize movement, clothes should be cut off of a patient once in a warm environment. (1 – Strong, B)
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Protection from further heat loss

Protect from further cooling by using insulation and vapor barriers until the patient has reached a warm environment, such as the warmed interior of an ambulance. Remove wet clothes, preferably by cutting them off, only when the patient has been protected from the cold. (1 – Strong, C)
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Insulate the patient from the ground (eg, with sleeping pads) to protect from conductive heat loss. Minimize heat loss from the head and neck by covering these areas as effectively as possible (eg, toque, watch cap, hood, jacket). (1 – Strong, C)
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Protection from windy conditions

An outer windproof layer should be used to protect the patient from wind and especially from rotor wash when loading or unloading from a helicopter. If possible, add a second vapor barrier against the victim to protect the insulating layers. (1 – Strong, C)
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FIELD REWARMING

Shivering

Shivering is an effective method of rewarming in a patient who is cold-stressed or mildly hypothermic. The patient must be adequately insulated from the environment to retain the generated heat. (1 – Strong, A)
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An alert patient who is shivering, and who is not at risk for aspiration, should receive high-carbohydrate liquids and/or food. Liquids and food may be warmed but should not be hot enough to burn the esophagus. (1 – Strong, C)
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Delay exercise to protect against afterdrop
A shivering patient who may be hypothermic should be kept as warm as possible, given calorie replacement, and observed before exercising. After this period of observation, the alert patient may be allowed to stand. If the patient can stand without difficulty, exercise intensity should start low and increase gradually as tolerated. The patient should be closely monitored; if the condition worsens, the patient should stop exercising and be treated accordingly. (1 – Strong, C)
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Active external rewarming

Active sources of heat should be used. (1 – Strong, B)
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Rewarming devices should be used in conjunction with vapor barriers and insulation. (1 – Strong, B)
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The Heat Pac should only be used outdoors or with proper ventilation that is carefully monitored to prevent CO accumulation. (1 – Strong, B)
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The single-package, small, and light HPMK is a practical system for transport in a single backpack and useful for military operations and should be used with an added layer of insulation if possible. (1 – Strong, C)
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Body-to-body rewarming

Body-to-body rewarming can be used in mild hypothermia to increase patient thermal comfort if enough personnel are available and it does not delay evacuation to definitive care. (1 – Strong, B)
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Applying heat to the axillae, chest, and back

Apply heat sources to the axillae, chest, and back. A large heat pad or blanket should be placed over the chest and, if large enough, extend into the axillae and under the back. (1 – Strong, B)
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Additional heat can be applied to the neck if precautions are taken to prevent heat loss through any neck opening. (1 – Strong, C)
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If application of heat to the chest is contraindicated (eg, CPR or some chest injuries), heat sources may be still be applied under the patient’s upper back or to the head. (1 – Strong, B)
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If applying heat sources to the back, rescuers must be able to observe for the development of burns on a regular basis. (1 – Strong, C)
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Protection of cold skin

Avoid localized pressure to cold skin. Apply heat sources according to manufacturer instructions; this often precludes direct contact with the skin by placing some thin insulating material between the skin and heat source to prevent burning the skin. (1 – Strong, C)
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Skin should be assessed every 20 to 30 min for excess reddening or other signs of impending thermal burns when active heat sources are being applied. (1 – Strong, C)
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Do not use small chemical heat packs for rewarming

Do not use small chemical heat packs for core rewarming of a hypothermic patient. (1 – Strong, B)
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However, these small chemical heat packs can be used to prevent local cold injury to the hands and feet during treatment and transport. (1 – Strong, C)
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Heated humidified oxygen

Heated humidified oxygen can be used in combination with other rewarming methods, (2 – Weak, C)
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but it should not be relied on as the only rewarming method. (1 – Strong, B)
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Do not use warm showers or baths for rewarming

A warm shower or bath should not be used for initial rewarming, even if a patient appears to be only mildly hypothermic. (1 – Strong, C)
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Distal limb warming

Distal limb warming to the elbows and knees in 42 to 45°C water can be used for rewarming a patient with mild hypothermia if the clinical setting is appropriate. (1 – Strong, C)
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Rewarming during transport

Forced air warming should be used during air or ground transport, if available. (1 – Strong, A)
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If forced air warming is not available, use of other heat sources can be continued. Care must be taken to prevent carbon monoxide CO buildup with the charcoal Heat Pac in a ground ambulance; this can be done by igniting the device outside the vehicle, bringing it inside only after initial smoke production subsides, ventilating the vehicle compartment, and monitoring CO. (1 – Strong, C)
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A charcoal Heat Pac should not be used in an aircraft. (1 – Strong, C)
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Temperature in air or ground ambulances

Patient compartments in ground and air ambulances should be heated to at least 24°C, if possible, to decrease further heat loss. (1 – Strong, C)
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Treatment of cold stressed patients who are not hypothermic

It is the consensus of the panel that a cold-stressed patient who is not hypothermic need not be kept horizontal. The patient may be allowed to remove his or her own wet clothing and to put on dry clothing without shelter, if necessary. The patient may be allowed to rest in a sitting position, to eat and drink to maintain energy reserves and hydration, and to move or keep moving, if necessary. These patients will need close monitoring to ensure they do not become hypothermic. (G-U, U)
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RESUSCITATION OF HYPOTHERMIC PATIENTS

Decision to resuscitate hypothermic patients without signs of life

Fixed, dilated pupils, apparent rigor mortis, and dependent lividity are not considered contraindications to resuscitation of a severely hypothermic patient. (1 – Strong, A)
(Evidence grade: 1A for fixed, dilated pupils and apparent rigor mortis)
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Rescuers should attempt CPR and resuscitation unless contraindications exist. (1 – Strong, A)
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Contraindications to resuscitation of hypothermic patients

Do not attempt to resuscitate a patient with obvious fatal injuries or whose chest wall is too stiff for compressions. (1 – Strong, A)
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Indication for cardiopulmonary resuscitation

Rescuers should make every effort to move the patient to a warm setting, such as a ground or air ambulance or a medical facility where cardiac monitoring is available to guide resuscitation and to start rewarming. (1 – Strong, C)
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Prior to starting CPR, feel for a carotid pulse for 1 min. If a pulse is not palpated after 1 min, start CPR, including rescue breathing. (1 – Strong, C)
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No cut-off temperature for resuscitation

Resuscitation attempts should be continued regardless of the measured core temperature. (2 – Weak, C)
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Electrocardiographic monitoring

CPR should be started if a nonperfusing rhythm, including ventricular tachycardia (VT), ventricular fibrillation (VF), or asystole, is detected. If there is a cardiac rhythm with organized QRS complexes, CPR should not be performed. (1 – Strong, C)
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unless end-tidal CO2 (ETCO2) monitoring confirms lack of perfusion or echocardiography shows that there are no cardiac contractions corresponding to electrical activity. (1 – Strong, C)
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Use maximal amplification on the monitor to search for QRS complexes. (1 – Strong, C)
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Delaying CPR, intermittent CPR, and prolonged CPR

Immediate, high-quality CPR should be performed for a hypothermic patient in cardiac arrest. If it is impossible or unsafe to perform immediate and continuous CPR, rescuers should perform delayed or intermittent CPR. Ideally, compressions will not be delayed for longer than 10 min, a conservative interval based on the uncontrolled nature of out-of-hospital hypothermic cardiac arrest. (1 – Strong, C)
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If CPR cannot be performed continuously, compressions should be performed for a minimum of 5 min, with interruptions between periods of compressions that should not exceed 5 min. (1 – Strong, C)
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CPR technique in hypothermia

Patients in cardiac arrest should have chest compressions delivered at the same rate as for normothermic patients. (1 – Strong, C)
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Using a mechanical compression device may decrease interruptions and reduce rescuer fatigue. (1 – Strong, C)
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Automated external defibrillator (AED)

If shock is advised by the AED, rescuers should attempt defibrillation and start CPR. If no shock is advised on an AED, no carotid pulse is found after palpating for at least 1 min, normal breathing or other signs of life are not observed, and ultrasound is not available to verify cardiac activity or pulse, start CPR. (1 – Strong, C)
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Initial defibrillation in hypothermia

If a monitor/defibrillator shows VT or VF in a patient whose core temperature is thought to be below 30°C, a single shock should be given at maximum power. (1 – Strong, C)
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Repeat defibrillation attempts in hypothermia

Wait until a patient has been rewarmed to 30°C before attempting further shocks. (2 – Weak, C)
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Once the core temperature reaches 30°C, follow defibrillation guidelines for normothermic patients. (1 – Strong, C)
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Airway management in hypothermia

The advantages of advanced airway management outweigh the risk of causing VF. (1 – Strong, C)
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A nasogastric or orogastric tube should be placed after the airway is secured to decompress the stomach. (1 – Strong, C)
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Ventilation in hypothermia without an advanced airway

In the absence of ETCO2 monitoring, ventilation should be delivered at the same rate recommended for a normothermic patient, unless an advanced airway is in place (see below). (2 – Weak, C)
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Ventilation in hypothermia with advanced airway

In a patient with an advanced airway, if ETCO2 monitoring is not available, ventilation should be delivered at half the rate recommended for a normothermic patient to avoid hyperventilation. (1 – Strong, C)
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Management of ETCO2

If ETCO2 monitoring is available, ETCO2 should be kept within the normal range. In rescues at altitudes above 1200 m, advanced life support personnel should be aware of the normal range of ETCO2 at a given altitude. (1 – Strong, C)
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Anesthetic and neuromuscular blocking agents in hypothermia

In patients with core temperatures lower than 30°C, dosages of anesthetic and neuromuscular blocking agents should be decreased, and intervals should be extended according to the degree of hypothermia. Current data are insufficient to recommend specific protocols. (1 – Strong, C)
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Supplemental oxygen

A hypothermic patient should receive supplemental oxygen, especially at altitudes over 2500 m, because of potential benefits and no known harm. (1 – Strong, C)
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Circulatory access in hypothermia

If circulatory access cannot immediately be obtained with a peripheral IV catheter, access should be obtained by the intraosseous (IO) method. (1 – Strong, C)
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Central venous access can be obtained using a femoral line if no other option is available. (1 – Strong, C)
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Volume replacement in hypothermia

Resuscitate a hypothermic patient with normal saline warmed to 40 to 42°C given IV or IO. Use caution to prevent volume overload. (1 – Strong, B)
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Fluid management in hypothermia

When practical, fluids should be given as boluses rather than by continuous infusion. (1 – Strong, C)
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The goal of fluid administration should be to maintain systolic blood pressure at a level that provides adequate perfusion, depending on the degree of hypothermia. (1 – Strong, C)
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Use of exogenous glucose and insulin in hypothermia

Glucose should be administered to the hypothermic patient who is hypoglycemic. (1 – Strong, A)
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Insulin is not initially indicated for hyperglycemia. (1 – Strong, B)
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If glucose testing is not available, IV glucose can be administered empirically to the hypothermic patient with altered mental status. (1 – Strong, C)
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Effects of vasoactive and antidysrhythmic drugs in hypothermia

The panel concurs that no recommendation can be made at this time owing to the limited evidence available. (, U)
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Dosing of drugs in hypothermia

Do not administer vasoactive drugs until the patient has been rewarmed to 30°C. (1 – Strong, C)
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To minimize the potential for toxic accumulation of medications, the usual dose can be given, but dosing intervals should be twice as long as usual when the core temperature is 30 to 35°C. (2 – Weak, C)
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Transcutaneous cardiac pacing in hypothermia

It is the consensus of the panel that transcutaneous pacing may be beneficial in hypothermia in the setting of bradycardia with hypotension disproportionate to the core temperature. (2 – Weak, C)
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Management of atrial dysrhythmias during rewarming of a hypothermic patient

No treatment is indicated for atrial dysrhythmias in a hemodynamically stable patient during rewarming. (1 – Strong, B)
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TRANSPORT/TRIAGE

Severe trauma

To prevent hypothermia, the severely injured patient should be treated early and aggressively with active rewarming during all phases of out-of-hospital care. (1 – Strong, B)
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Stabilizing injuries for transport

When preparing a patient for transport, potential spinal injuries should be stabilized. (1 – Strong, C)
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Fractures and dislocations should be reduced as much as possible to normal anatomic configuration. (1 – Strong, C)
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Open wounds should be covered. (1 – Strong, C)
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Patients with mild hypothermia who are alert

An uninjured patient who is completely alert and shivering may be treated without being transported to a hospital. (1 – Strong, B)
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Choice of destination hospital for hypothermic patients

Patients who are not profoundly hypothermic or hemodynamically unstable should be transported to the nearest facility. (G-U, U)
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Hypothermic patients with hemodynamic instability

A patient with moderate to severe hypothermia who is hemodynamically stable can be transferred to the closest hospital or other appropriate medical facility, such as a rural clinic. (1 – Strong, C)
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A patient who is hemodynamically unstable or with a core temperature <28°C should be transferred to a hospital capable of providing critical care and extracorporeal life support (ECLS). If this will require significant additional time—generally more than an additional hour—of noncritical care transport, the patient should first be stabilized at a closer facility. (1 – Strong, C)
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A patient in cardiac arrest should be transferred to a hospital capable of providing ECLS if possible. If all other factors are equal, ECMO is preferable over CPB. (1 – Strong, B)
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In geographic regions where there is no hospital capable of providing ECLS or when a hospital capable of providing ECLS is not accessible, transport a patient in cardiac arrest to the closest hospital where serum potassium can be measured and resuscitation methods not involving ECLS can be attempted for a patient whose serum potassium is <12 mmol·L-1. (1 – Strong, C)
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Hypothermic patients who are alert but have comorbidities, including trauma or asphyxia

A patient with injuries meeting trauma criteria should be transported to a trauma center. (1 – Strong, B)
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The asphyxiated patient should be transported to a hospital for observation. (1 – Strong, B)
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Use of biochemical markers to determine if resuscitation should be continued in a hypothermic patient without vital signs

If an adult hypothermic patient has a potassium >12 mmol·L-1, CPR should be terminated. (1 – Strong, B)
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Recommendation Grading

Overview

Title

Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia

Authoring Organization

Publication Month/Year

December 1, 2019

Last Updated Month/Year

June 9, 2022

Supplemental Implementation Tools

Document Type

Guideline

External Publication Status

Published

Country of Publication

US

Inclusion Criteria

Female, Male, Adolescent, Adult, Older adult

Health Care Settings

Ambulatory, Emergency care, Hospital, Medical transportation

Intended Users

Physician, nurse, nurse practitioner, physician assistant

Scope

Prevention, Management, Treatment

Diseases/Conditions (MeSH)

D007035 - Hypothermia

Keywords

resuscitation, rewarming, hypothermia, cold, shivering

Methodology

Number of Source Documents
138
Literature Search Start Date
January 1, 2013
Literature Search End Date
October 9, 2019