Baby, It’s Cold Outside: Death by Hypothermia

The Basics:

  • On average, approximately 1300 Americans die of hypothermia each year 
  • These don’t all occur in cold mountain regions. Homelessness, mental illness and substance abuse are important risk factors, particularly in urban areas. 
  • Not all hypothermia cases are related to exposure! Other causes include hypoglycemia, hypothyroidism, hypoadrenalism, hypopituitarism, CNS dysfunction, drug intoxication, sepsis and dermal disease 
  • Hypothermia = core body temperature < 35 degrees C (95 degrees F) 
  • Mild hypothermia (32-35 degrees C): present with shivering, tachycardia, tachypnea and hypertension 
  • < 32 degrees C: shivering stops and HR and BP decrease; patients become confused, lethargic and then comatose; Reflexes are lost, RR increases; bronchorrea occurs; aspiration is common; cold diuresis and hemoconcentration occur 
  • As temp lowers, sinus bradycardia develops into atrial fibrillation with slow ventricular response to ventricular fibrillation to asystole. At temps < 30 degrees C, the risk for dysrhythmias increas

Rewarming and Managment:

  • Type of rewarming is based on cardiovascular status, NOT temperature 
  • Passive rewarming: removal from cold environment and wet clothes, insulation 
  • Active external rewarming: warm water immersion, heating blankets set at 40 degrees C, radiant heat, forced air 
  • Active core rewarming at 40 degrees C: Inhalation rewarming (warm air via the vent), heated IV fluids, GI tract lavage, bladder lavage, peritoneal lavage, pleural lavage, extracorporeal rewarming, mediastinal lavage by thoracotomy 
  • Remember to handle these patients gently to avoid precipitation of ventricular fibrillation!

ECMO in Hypothermic Cardiac Arrest?:

  • The use of ECMO has been recommended as the rescue therapy of choice for hypothermic cardiac arrest for its ability to rapidly rewarm patients (8-12 degrees/hour) and provide complete cardiopulmonary support 
  • Studies have shown that patients with cardiac arrest have a rate of survival of 50% with the use of ECMO, whereas, at centers without ECMO, these same types of patients have a survival rate of only 10% 
  • Cases of survival with a good clinical outcome have been reported with core temperatures as low as 13 degrees Celsius and in cases requiring long transport with more than 5 hours of CPR!

Risk Factors for Poor Prognosis Despite Aggressive Therapy (ECMO, etc):

  • Clear history of cardiac arrest before cooling 
  • Obvious signs of irreversible death 
  • Core body temperature higher than 32 degrees Celsius with asystole 
  • Potassium greater than 12 mEq/L

1. Ginty C, Srivastava A, Rosenbloom M, Fowler S, Filippone L. Extracorporeal membrane oxygenation rewarming in the ED: an opportunity for success. Am J Emerg Med. 2015 Jun:33(6):857.
2. Tintinalli, J. E., Stapczynski, J. S., Ma, O. J., Yealy, D. M., Meckler, G. D., & Cline, D. (2016).Tintinalli's Emergency Medicine: A Comprehensive Study Guide. Chapter 18: Frostbite and Hypothermia. New York: McGraw-Hill Education.