Let’s step back and talk about the basic but very important subject of fever.  As days shorten and temperatures cool, we’ll frequently be facing winter illnesses with fever.  It is the most common symptom prompting visits to the doctor, as well as a frequent cause of late night distress for children, parents (and pediatricians!).

So, what’s going on?  The hypothalamus of the brain is the body’s thermostat, maintaining basal body temperature at 97.6-100.2 F(36.2-37.8 C).  At night, our body’s diurnal variation dictates that our temperature is higher later than early in the day.  Rectal temperatures above 100.2 F are fever.  All human beings are normally in that range ( No person “runs low” normally).  When presented with an infection–viral or bacterial–white blood cells release pyrogens that raise the hypothalamic set point and the body temperature rises.

Why does this happen?  At higher temperatures most microbes reproduce and spread less effectively.  Also, white blood cells become more active and move toward and attack the infection better.  Of course, there are adverse effects as well.  Much of the discomfort associated with typical infectious illnesses–muscle and headaches, fatigue–are due to fever.  Most fevers are not primarily dangerous, however.  The human body can function very adequately at high temperatures and for a surprisingly long time.  Above 106 F (41.1 C) cardiac function and nerve conduction can deteriorate, and enzyme systems can malfunction.  Below this there are few serious effects.  Except in susceptible individuals (eg, family history) higher temperatures rarely cause seizure.  They do not cause brain damage or sterility.

So what to do? Moderate the child’s activity as much as reasonable.  Don’t overheat or overcool their environment.  Dress them appropriately (light clothing and thin blankets).  Bathe or sponge the child with lukewarm water (never use alcohol).  Use acetaminophen every 4 hours (orally or rectally) or ibuprofen every 6 hours (orally).  Never treat a febrile child with aspirin as it can cause Reye Syndrome, a severe liver ailment.  Also, be careful with acetaminophen dosing, as too much of this drug can also cause liver damage.

When should one become concerned?  Fever above 104 F( 40 C) or for greater than 72 hours.  Fever later in the course of an illness.  Fever in a child under 2 months of age.  A febrile child who is too listless to drink regularly or who vomits frequently and hasn’t voided in 8-12 hours.  Fever associated with severe cough or pain.  You should call if your child meets any of these criteria.

Remember, things are rarely as serious in reality as they are in our minds (especially at night!).  However, I always remind parents that if they have serious doubts about any situation, it’s always best to call so we can try and work it out together.

Please post comments or questions for future posts, and, as always, thanks for reading.


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