Evaluating Hyperpyrexia During a Very Hot Summer

Paul G. Auwaerter, MD


August 10, 2011

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Hi. Paul Auwaerter here, speaking for Medscape Infectious Diseases, with a seasonal topic. Much of the United States has been gripped in an extensive heat wave. A recent question to me from our emergency department prompted the question of whether infections can cause extraordinarily high temperatures. Hyperpyrexia has been defined by some as temperatures of 106° Fahrenheit (F) or higher. That translates to 41.1° Celsius (C). Some people use the term "extreme hyperpyrexia" (41.5° C/106.7° F).

Here is the scenario. I had a call from the emergency department from one of the attendings. It was one of these terrible days in Baltimore, high temperatures, more than 100°. They had a patient, a man, who was delirious. They knew very little of his history, but his temperature was 106.2° F. The attending asked a simple question: could an infection cause that high a temperature? He said he had been taught that infections don't cause temperature elevations higher than 106°. This is something that, in the infectious disease world, I have heard as well -- that very high temperatures (more than 105°, for example) could be caused by malaria or certain viral infections such as influenza or Dengue fever, but really, infection drops down on the list when the temperature reaches 105°. At a temperature of 106°, you may not even consider infection.

I decided to try to find out more about this and see if this information was merely passed on through the ages or is really based on some sound science. I started to do some investigations and found the following. A number of studies have well-documented children presenting with hyperpyrexia (more than 106°) with significant rates of not only viral infection but also bacterial infection. In fact, the article by Trautner[1] and the other pediatric article[2] found that a substantial number of children, upwards of 40% or more, had infections as a cause of their hyperpyrexia. Sioson and colleagues[3] examined adults and found (although this dates from many years ago) 39 adults with hyperpyrexia, and 94% of that group had an infectious etiology: bacterial, fungal, or viral.

The conventional wisdom, or the teaching, that infections are not a cause of hyperpyrexia is false[4] and, therefore, it could be very dangerous for a patient if you took that approach. How can you tell what might be a fever driven by an infection vs hyperthermia, which might be a consequence of heat stroke being outside in extreme temperature? This is where you have to rely on clinical attributes. Hyperthermia is the failure of the body to adapt to external forces, so the body cannot cool sufficiently. Fever is driven by different pathophysiology. Typically, patients suffering from hyperthermia have hot, dry skin. Patients who have infection might be warm or moist or sweaty. Also, antipyretics will help reduce fevers of infectious origin but will do little for patients who have hyperthermia, malignant hyperthermia syndrome, or one of the noninfectious causes of hyperthermia.

This is just a quick blog that I hope corrects some of you who may have the misconception that I had, that infections are not a cause of hyperpyrexia, and to remind you to keep it on the list, be thoughtful, consider it, and evaluate your patients. The references below help support some of these thoughts. Stay cool this summer. Thanks so much for listening.


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