UMEM Educational Pearls

Title: Environmental Hyperthermia: Is it heat exhaustion or heat stroke?

Keywords: Hyperthermia, heat stroke, environmental (PubMed Search)

Posted: 9/1/2014 by Jon Mark Hirshon, PhD, MPH, MD (Updated: 9/3/2014)
Click here to contact Jon Mark Hirshon, PhD, MPH, MD

Hyperthermia can be defined as a core body temperature > 38.5ºC. In contrast to fever, the body’s temperature rises uncontrollably and the body is not able to dissipate the heat. There can be many causes of hyperthermia, including from environmental exposure.

There are two main environmental heat illnesses, heat exhaustion and heat stroke.

Heat exhaustion:

Vague malaise, fatigue, headache
Core temperature may be normal or elevated (below 40ºC)
May have tachycardia, orthostatic hypotension, clinical dehydration
Liver function tests (transaminases) may be normal or elevated
IMPORTANT- there is no altered mental status (i.e.: no coma or seizures)

Heat stroke

Usually tachycardia, orthostatic hypotension, clinical dehydration
May have hot, dry skin, but not always
Liver function tests (transaminases) are markedly elevated
May have rhabdomyolysis and renal failure
IMPORTANT- Signs of altered mental status (i.e.: coma, seizure, delirium)
Mortality may be up to 33%

Bottom line:

Heat stroke is a life threatening emergency.
- Early recognition and rapid appropriate therapy can save a life
The most effective cooling is evaporative cooling along with ice packs

References

Management of the hyperthermic patient. Calvello EJ, Hu K, Khoujah D. Br J Hosp Med (Lond). 2011 Oct;72(10):571-5

Cooling Techniques for Hyperthermia by Schraga ED, Kates LW. Available at: http://emedicine.medscape.com/article/149546-overview