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