From the Guidelines
In hypothermic cardiac arrest, ACLS protocols should be modified rather than followed as usual, with a focus on rewarming the patient and continuing resuscitative efforts until the patient reaches normal body temperature. According to the 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1, full resuscitative measures, including extracorporeal rewarming when available, are recommended for all victims of accidental hypothermia without characteristics that deem them unlikely to survive and without any obviously lethal traumatic injury.
Key Considerations
- Initiating CPR immediately is crucial, but defibrillation attempts may be performed according to the standard BLS algorithm concurrent with rewarming strategies 1.
- Administration of epinephrine during cardiac arrest may be considered according to the standard ACLS algorithm concurrent with rewarming strategies 1.
- Active rewarming is the priority and should occur simultaneously with resuscitation efforts, using methods such as warm blankets, forced-air warming systems, warm IV fluids, warm humidified oxygen, peritoneal lavage with warm fluids, or extracorporeal membrane oxygenation (ECMO) in severe cases.
- The patient should not be considered dead before rewarming has been provided unless there are signs of obvious death 1.
Rationale
The modifications to ACLS protocols are necessary because hypothermia slows metabolism, decreases drug clearance, and can cause arrhythmias that are resistant to both medications and defibrillation when the heart is cold. As stated in the guidelines, "a patient isn't dead until they're warm and dead" - resuscitation efforts should continue until the patient reaches normal body temperature, as successful resuscitation has been documented even after prolonged cardiac arrest in severely hypothermic patients 1.
From the Research
Advanced Cardiovascular Life Support (ACLS) in Hypothermic Cardiac Arrest
- The application of ACLS in severe hypothermic cardiac arrest remains controversial 2
- Some studies suggest that standard ACLS protocols can be effective in resuscitating hypothermic cardiac arrest patients, even with minimal increase in core temperature 3, 2
- In cases of accidental hypothermia with cardiac arrest, rapid institution of full cardiopulmonary bypass provides excellent circulatory support and rapid rewarming, avoiding complications of prolonged inadequate circulation 4
- Other rewarming techniques, such as peritoneal lavage, intravascular warming catheter, and renal replacement therapy, can be beneficial, but extracorporeal life support is recommended as the preferred rewarming method 5
Rewarming Strategies
- Active and passive rewarming can be initiated without extracorporeal rewarming, and may be effective in achieving return of spontaneous circulation (ROSC) 3
- Rewarming rates of greater than 4 °C/h can be achieved with less invasive approaches, such as the use of a ZOLL Icy catheter 5
- The optimal rewarming technique, use of epinephrine, and time when defibrillation should be attempted remain controversial in patients with severe accidental hypothermia in cardiac arrest 3
Case Reports
- A 42-year-old female was successfully resuscitated from ventricular fibrillation with a core body temperature below 28 °C using ACLS protocol and multimodal rewarming, including active internal rewarming via a ZOLL Icy catheter 5
- A 47-year-old man was successfully resuscitated from a ventricular fibrillation arrest with a core body temperature of 26.4 degrees C using ACLS protocols 2
- A patient with severe accidental hypothermia due to cold exposure associated with acute alcohol intoxication achieved ROSC at a core temperature of 23.8°C using standard ACLS procedures 3