The Lowdown on Fever

November 30, 2010

The Lowdown on Fever

Fever (pyrexia) is one of the most common complaints that I see in the clinic.  Determining what is the cause of the fever is not always easy to do.   Clinical work up often involves determining when the fever started, how high it has been, what treatment has been tried and any other symptoms that may be related to the issue at hand.  However, I find myself doing a lot of education about fever and dispelling myths and concerns surrounding rises in temperature.

First a lets discuss what is a normal body core temperature range.  Normally the body will fluctuate in temperature throughout the day, up to as much as an entire degree.  If you are a female this will also fluctuate around the time of the menstrual cycle.   Teething does cause a increase in body temperature but not over 100°F.   The National Institute of Health (NIH) gives a range of 97° F (36.1°C) to 99°F (37.2°C) as normal for body core temperature.  So when I have someone tell me they have a “low grade fever,” I tend not to get too excited.  The term “low grade fever” also brings back bad medical school memories as I used this term once on hospital rounds.  I was then informed, rather sternly, by my attending physician that a patient either has a fever or not.  He then proceeded to ask if I would ever tell a patient they had “low grade cancer,” because you either have cancer or not.   This same physician also chastised a friend of mine for using the term “temperature” instead of fever only to be told that everything has a temperature, even corpses and dog excrement (though that was not the exact words used.)  Needless to say medicine, and those who practice it tend to be very strict and unwavering in the use of terminology and definitions.

Fever as a symptom is a sign of an illness or infection.  This may either be from a bacterial or more often a viral source.  Other causes of fever include heat exhaustion, sunburns, inflammatory diseases and sometimes cancers.  It should be noted that the degree of fever does not necessarily indicate the seriousness of the underlying condition.  Minor illnesses may have a high fever while a more serious condition may have cause a lower fever.  Any child under the age of 3 months with a fever needs to be seen immediately by a physician.  There are cases when it is not possible to determine the cause of the fever.  If a fever persists for longer than a few weeks with a normal work up, this is termed Fever of Unknown Origin.

Fevers start as a response from the hypothalamus to some alteration of the normal healthy state of the human body (homeostasis).  When fever starts and the body tries to elevate its temperature, you get chills and shiver to generate heat in response to an illness.  When the fever “breaks” and tries to return to normal, you sweat to get rid of the excess heat.

Many parents have the same concern about fever.  This involves complications that may come from the fever.  Often the fever causes more angst for the parent than it does the child.  That is why I encourage the use of thermometers and NOT the hand.  There is no way to tell if someone has a fever by use of the palm of the hand.  Treating a fever found by a hand to the forehead is risking giving a medication that may not be needed and all medications have their risks.  Very often I feel people that are warm to the touch but have normal temperatures.

Other concerns include neurological damage.  Brain damage generally will not occur unless the fever exceeds 107.6 °F (42°C).  Untreated fevers caused by infections seldom increase over 105°F unless the patient is over dressed, bundled, or confined in a hot place.  Febrile seizures occur in children age 6 months to 5 years and happen more often in boys than girls.  This is the result of a sudden rise and fall in body core temperature and not to the overall maximum fever itself.  The vast majority of cases leave no lasting neurological effects.  Often this can run in families.  If this happens, the child should be seen by a physician do help determine the cause of the fever itself.

When treating a fever, Tylenol and Motrin are often the medications of choice.  Parents need to remember that Motrin (ibuprofen) should not be used in children under 6 months of age.  Aspirin should also not be used in children, as there is a risk of developing Reye’s syndrome, which is a disease of the liver.  Aspirin is very effective as an anti-pyritic (fever reducer) in adults and does not carry this risk.  There has been a lot of press about the use of Tylenol and Motrin in young children due to accidental overdosing.  All doses of these medications are weight based and your health care provider can help you determine the correct dose.   Do not use an ice bath or alcohol rubs to treat fevers as they cause shivering and will actually increase the body core temperature.  Remember the goal is to decrease the fever, not to eliminate it because the body is trying to fight off an illness. At the end of all my clinic visits I encourage parents and my patients that, when in doubt, call me.  There is a great fever algorithm that can be found at familydocotor.org.

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