Cardiac Arrest in Unintentional Hypothermia

Severe hypothermia (body temperature <30°C [86°F]) is associated with marked depression of critical body functions, which may make the victim appear clinically dead during the initial assessment.

Lifesaving procedures should be initiated unless the victim is obviously dead (eg, rigor mortis, decomposition, hemisection, decapitation).

The victim should be transported as soon as possible to a center where aggressive rewarming during resuscitation is possible.

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Initial Care for Victims of Unintentional Hypothermia

When the victim is extremely cold but has maintained a perfusing rhythm, focus on interventions that prevent further loss of heat and begin to rewarm the victim immediately.

  • Passive rewarming is generally adequate for patients with mild hypothermia (temperature >34°C [93.2°F]). Remove wet garments and insulate the victim from further environmental exposures to prevent additional evaporative heat loss.
  • External warming techniques such as forced air or other efficient surface-warming devices are appropriate for patients with moderate (30°C to 34°C [86°F to 93.2°F]) hypothermia with a perfusing rhythm. Passive rewarming alone will be inadequate for these patients.
  • Core rewarming is often used for patients with severe hypothermia (<30°C [86°F]) with a perfusing rhythm. Some have reported successful rewarming with active external warming techniques.
  • Patients with severe hypothermia and cardiac arrest can be rewarmed most rapidly with cardiopulmonary bypass.
  • Alternative effective core rewarming techniques include warm-water lavage of the thoracic cavity and extracorporeal blood warming with partial bypass.
  • Adjunctive core rewarming techniques include warmed intravenous or intraosseous fluids and warm humidified oxygen. Heat transfer with these measures is not rapid and should be considered supplementary to active warming techniques.

Do not delay urgent interventions such as airway management and insertion of vascular catheters regardless of evidence of cardiac irritability.

In the field, providers who have the time and equipment to assess core body temperature or to institute aggressive rewarming techniques should do so.

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BLS Modifications

When the victim is hypothermic, pulse and respiratory rates may be slow or difficult to detect, and the ECG may even show asystole.

If the hypothermic victim has no signs of life, begin CPR without delay. If the victim is not breathing, start rescue breathing immediately.

If VF or pulseless VT is present, attempt defibrillation.

If VF or pulseless VT persists after a single shock, the value of deferring subsequent defibrillation attempts until a target temperature is achieved is uncertain. It may be reasonable to perform further defibrillation attempts according to the standard BLS algorithm, concurrent with rewarming strategies. (Class IIb, LOE C) (2010 Part 12)

To prevent further loss of core heat, remove wet garments and protect the victim from additional environmental exposure. Insofar as possible, this should be done while providing initial BLS therapies. Rewarming should be attempted when feasible.

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ACLS Modifications

For unresponsive patients or those in arrest, advanced airway insertion is appropriate as recommended in the ACLS guidelines. Advanced airway management enables effective ventilation with warm, humidified oxygen and reduces the likelihood of aspiration in patients in prearrest.

ACLS management of cardiac arrest due to hypothermia focuses on aggressive active core rewarming techniques as the primary therapeutic modality.

The serum potassium will fall as hypothermia develops and rise as the patient is rewarmed. Severe hypothermia and resultant tissue damage, by contrast, may cause a subsequent rise in the serum potassium,

During cardiac arrest, it may be reasonable, concurrent with rewarming strategies, to consider administration of a vasopressor according to the standard ACLS algorithm. (Class IIb, LOE C) (2010 Part 12)

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Post-Cardiac Arrest Care

After ROSC, patients should continue to be warmed to a goal temperature of approximately 32° to 34°C; this can be maintained according to standard post-cardiac arrest guidelines for mild to moderate hypothermia in patients for whom induced hypothermia is appropriate. For those with contraindications to induced hypothermia, rewarming can continue to normal/baseline temperatures.

Because severe hypothermia is frequently preceded by other disorders (eg, drug overdose, alcohol use, or trauma), look for and treat these underlying conditions while simultaneously treating hypothermia.

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Withholding and Cessation of Resuscitative Efforts

Multiple case reports have documented survival from unintentional hypothermia even with prolonged CPR and prolonged arrest times. Thus, patients with severe unintentional hypothermia and cardiac arrest may benefit from longer attempted resuscitation even in cases of prolonged arrest time and prolonged CPR. Low serum potassium may be associated with hypothermia, and not hypoxemia, as the primary cause of the arrest. Patients should not be considered dead before warming has been provided.

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References

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