Hypothermia as a H&T Cause of Cardiac Arrest

A saying in emergency medicine is that hypothermic patients aren’t dead until they are warm and dead.  This is because patients have been known to survive long down times when they’re hypothermic.  There are documented cases of patients in cold-water drowning that have been underwater for over 30 minutes who are rewarmed, successfully resuscitated, and subsequently discharged from the hospital with little to no brain damage.  Hypothermia as a H&T cause of cardiac arrest is today’s Pass ACLS tip topic.

For purposes of discussing reversible causes of cardiac arrest, we’re discussing accidental hypothermia. When a patient’s core temperature drops below 96.8 F (36 C) we say that they are hypothermic.  As the body’s temperature drops below 36 C, hypothermia may further be classified as moderate or severe.  Moderate if the patient’s body core temp is between 30-34 C and severe if it’s below 30.

Severe Hypothermia

For patients with a body core temp less than 30 C, we do not give antiarrhythmic medications such as Lidocaine or Amiodarone.  Our primary functions for these patients are aimed at keeping vital organs alive with good CPR and:

  • defibrillating VFib or pulseless VTach if present;
  • administering only epinephrine; and
  • rewarming the patient’s core as rapidly as possible.

Rewarming patients with severe hypothermia usually involves invasive procedures so that we can warm the body’s core.  Some examples of rewarming interventions may include:

  • administration of warmed IV fluids;
  • warmed/humidified oxygen;
  • body cavity lavage; and
  • placing the patient on a heart/lung bypass.

In severe hypothermia we do not attempt passive/external  rewarming.  Warming the body from the outside can lead to rewarming shock and severe acidosis.

Moderate Hypothermia

Hypothermic patients with a body core temp of 30-34 C have moderate hypothermia.  For these patients, we follow our usual ACLS algorithms and provide good CPR, defibs, and medications (including antiarrhythmics) as usual.  Additionally, we should begin actively warming the patient.

External warming actions such as removing cold/wet clothing and wrapping the patient in a warm blanket may be helpful for patients with moderate hypothermia and can be started prehospital if local protocols allow.

Calling The Code

Because cold-water drowning and hypothermic patients have been known to survive long down times with little to no brain damage, in both moderate and severe hypothermia, we should continue resuscitation efforts until the patient has been rewarmed to a core temperature of at least 36 C.

Hypothermic patients are not dead until they are warm and dead.

 

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