How Warm is Warm and Dead?

“No one is dead until they are warm and dead.”  This is a mantra that is commonly used when caring for acute submersion injuries or cardiac arrest in cold environments.  Sure, it makes sense, but what is the data behind this mantra and how warm is warm enough?  As medicine goes, the answers are shades of grey rather than black and white. 

 

Hypothermia can be divided into mild, moderate, and severe ranging from 32-35C, 28-32C, and less than 28C, respectively.  Mild hypothermia can generally be treated with passive external rewarming techniques such as removing wet clothes and applying warm, dry blankets.  Moderate hypothermia requires active external rewarming using a Bair Hugger, and applied heat packs.  Once the core temperature drops below 28C, active internal rewarming is indicated via warm intravenous fluids, gastric or bladder lavage, chest tube insertion and pleural lavage, and even extracorporeal membrane oxygenation (ECMO) is severe cases. 

 

The above mantra stemmed from case reports of mainly pediatric drownings that obtained return of spontaneous circulation (ROSC) after prolonged resuscitation efforts.  Because of these miraculous recoveries with good neurologic outcomes, many care providers became hesitant to early cessation of resuscitation.  However, it is important to note that the survivors were generally healthy children, submerged in water less than 10 degrees Celsius, who had initial core body temperatures less than 20 degrees Celsius.  One could argue that the “warm and dead” mantra may not apply to the adult with comorbidities submerged in water warmer than 10C. 

 

Regardless, there is some data out there to help guide resuscitation efforts.  By sampling several emergency medicine textbooks as well as several studies, most recommend resuscitation and rewarming efforts until core temperatures range from 30-35 degrees Celsius.  No two recommendations are the same, which reflects the uncertainty that surrounds this body of evidence.  Most would settle on a cutoff around 32C, the point at which neuroprotection related to hypothermia is lost. 

 

A final important note regarding resuscitation in the setting of hypothermia is the use of standard ACLS protocols.  With core temperatures less than 28 degrees Celsius, standard ACLS medications such as epinephrine, as well as defibrillation have been shown to be ineffective and occasionally harmful.  This is secondary to the drastic alteration in physiology and protein composition at such low temperatures.  As the patient is rewarmed, toxic levels of ACLS drugs may lead to impending arrest and demise.  The literature would suggest a single dose of epinephrine and a single attempt at defibrillation if core temperatures are below 28C.  If unsuccessful, resuscitation should focus on quality chest compressions and active internal rewarming techniques.  Once the core temperature is above 28C, standard ACLS can be resumed. 

 

Perhaps the most important aspect of resuscitation of the hypothermic patient is to make decisions on a case-by-case basis.  The unique neuroprotective effects of hypothermia and the altered physiology at severe temperatures create unique circumstances that need to be addressed as such. 

 

References:

¡  Stephen et al. “Hypothermia”, Chapter 130, Emergency Medicine, Adams, Saunders and Elsevier, 2008.

¡  Aish et al. “Submersion Injuries”, Chapter 133, Emergency Medicine, Adams, Saunders and Elsevier, 2008.

¡  Fleeger et al. “Guidelines for pediatric advanced life support”, UpToDate, May 2011.

¡  Chandy et al. “Submersion Injuries”, UpToDate, June 2011.

¡  Corneli et al. “Treatment of Hypothermia in Children”, UpToDate, October 2009.

¡  Bessen et al. “Hypothermia”, Chapter 203, Tintinalli’s Emergency Medicine, McGraw-Hill, 2011.

¡  Causey et al. “Drowning”, Chapter 209, Tintinalli’s Emergency Medicine, McGraw-Hill, 2011.

¡  Danzl, Daniel. “Accidental Hypothermia”, Chapter 138, Rosen’s Emergency Medicine, Mosby and Elsevier, 2010.

¡  Richards et al. “Drowning”, Chapter 143, Rosen’s Emergency Medicine, Mosby and Elsevier, 2010.

¡  Gilbert M, Busund R, Skagseth A, et al. Resuscitation from accidental hypothermia of 13.7 degrees C with circulatory arrest. Lancet 2000; 355:375.

¡  Bolte RG, Black PG, Bowers RS, et al. The use of extracorporeal rewarming in a child submerged for 66 minutes. JAMA 1988; 260:377.

 

This review submitted by Dr. Nicholas Borm