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Your child has a fever - Now what? Today's Approach To Treat Fever

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Understanding your child's fever

A fever (pyrexia) is defined as an elevation of body temperature above the normal range, due to a change in the body’s temperature set-point. A fever should not be confused with hyperthermia. Hyperthermia is an elevation of body temperature due to the inability of the body to dissipate heat as rapidly as heat is being accumulated.


What constitutes a fever?

A fever (pyrexia) is defined as an elevation of body temperature above the normal range, due to a change in the body’s temperature set-point. A fever should not be confused with hyperthermia. Hyperthermia is an elevation of body temperature due to the inability of the body to dissipate heat as rapidly as heat is being accumulated. Heatstroke is a good example of hyperthermia. Depending on severity, both conditions may require medical attention; however, treatment methods may vary. For example, medicines like aspirin or Tylenol aren't used to treat hyperthermia.

What is the normal range?

It is important to know your child’s normal temperature, i.e. the temperature before they get sick. People can have variable temperatures and without having a baseline, it is hard to know if a mild temperature really constitutes a fever.

To do this, take your child’s temperature 8 times over a two week period. Be sure to get readings for different times of the day, e.g. morning, around lunch time, in the afternoon and at bedtime. Two readings for each time would be ideal. Then average the 8 numbers. You may note that your child’s temperature varies at different times of the day. This is normal. Most people have a higher temperature when they wake up than when they go to bed. Now that you have a baseline value for your child, it will be easier to tell if they have a fever. Be sure to write the baseline temperature down so you don’t forget it.

The normal range of temperature is 97.7 – 99.5 F (36.5 – 37.5 C). If your child is within this range you probably shouldn't view it as a fever. However, if your child’s baseline temperature is 97.4 F , for example, and they have a temperature if 99.2 F, that would be considered a fever. This is why knowing your child’s baseline is important. This information is also important for your doctor to know.

What causes a fever?

Deep in the brain is a small structure called the hypothalamus. The hypothalamus regulates many very important body functions, including body temperature. It has an internal set-point and uses the autonomic nervous system to make sure the core body temperature does not drift far for this set-point value. In most cases, body temperature is managed by changes in sweating and the amount of blood flowing through the peripheral blood vessels.

A fever occurs with something changes the set-point and the hypothalamus begins to stimulate the autonomic nerves in an effort to establish a new, higher, core temperature.

Chemicals called pyrogens have the ability to induce a fever by altering the se-point in the hypothalamus. Pyrogens can be subdivided into pyrogens produced by our own body (endogenous) and pyrogens produced by bacteria (exogenous). Internal pyrogens are produced in response to certain allergic reactions (hay fever), immune reactions in conditions such as Lupus, and in response to cell and tissue damage (cancer, infarction, gout and viral infections). Exogenous pyrogens are produced by bacteria and like endogenous pyrogens they can change the body temperature set-point in the hypothalamus.

Once the set-point has been elevated the hypothalamus begins the process of raising the body’s temperature to the new (artificial) set-point. The hypothalamus starts by creating the sensation of being cold, which leads the person to participate in heat seeking or heat conserving behaviors.

Additionally, the hypothalamus causes vasoconstriction, which reduces the blood flow to the skin, making the person look pale. If more is needed to raise the temperature, then the hypothalamus increase general metabolism and increases muscle tone up to and including shivering. The heat generating processes quickly brings the body temperature up to the new set-point and we say the person has a fever. Once the body reaches the new set point, the person will feel some slight improvement in their condition as the hypothalamus relaxes its temperature raising processes. The hypothalamus will now maintain the new set-point until the pyrogen or its source is destroyed.

Typical symptoms of a fever

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Symptoms of fever include:

• Chills
• Shivering (not present in newborns and infants)
• Heat seeking / Heat conserving behaviors
• Lack of energy / Fatigue (lethargy)
• Mental changes (Depression / Confusion / Difficulty concentrating)
• Loss of appetite
• Disturbed sleep patterns
• Hallucinations (very high fever)
• Seizures (very high fever)

Why do we get fevers?

There is good evidence to suggest that fevers have a physiological benefit, assuming they don’t go too high. In general, our immune system is more aggressive during a fever, which improves its pathogen fighting abilities. Additionally, many bacteria and viruses are less active and reproduce slower at higher temperatures, which is also helpful to our immune system and helps speed recovery.

Most fevers are self-limiting and rarely rise to dangerous levels. While not at all pleasant, adult temperatures less than 103 F (39.4) are not dangerous and can be tolerated for short periods of time (1-3 days). For children the value that is dangerous is lower. An infant or child’s temperature should not be allowed to exceed 101 F (38.3 C).

There’s not always a correlation between fever and severity of illness.

Don't be confused into thinking that a high fever means a serious illness and a low fever means a mild illness. This is NOT always true and sick children need to be monitored carefully regardless of fever.

How should a fever be treated?

Today’s approach is to not treat low-grade fevers. As mentioned above, fever is an effective tool in our immune systems’ toolbox. Additionally, most fever reducing medications are also painkillers or anti-inflammatory drugs. These drugs may hide or mask important symptoms. For example, joint aches, headaches or muscle pain / stiffness could be very important for a proper diagnosis, but might be unreported or under-reported while taking pain killers and/or anti-inflammatories.

If you decide that the fever needs to be brought down, it can be lowered with acetaminophen or ibuprofen (anti-pyretics). Both drugs are very effective. Acetaminophen is also a potent painkiller and ibuprofen is a potent painkiller and a good anti-inflammatory drug. Aspirin can be used in adults, but NOT in children or teenagers. Aspirin is both a painkiller and an anti-inflammatory drug. The use of aspirin, during recovery from viral infections, has been linked to a rare and serious condition called Reye’s syndrome. It is generally recommended that aspirin not be used to treat viral fevers and should only be used by adults. Since differentiating between a viral fever and fevers from other causes is often quite difficult, it is a good rule to not use aspirin to treat fevers, especially since there are other equally good choices. As with any drug, consult with your physician before giving to your child.

What if the fever won't go down?

If the fever is high or persistent, call your doctor. Most fevers respond very nicely to the recommended doses of acetaminophen. Do not increase the dose in an effort to lower the temperature. Acetaminophen has a very narrow safety profile and it is very easy to give doses large enough to damage a child’s immature liver. Acetaminophen poisoning is the leading cause of acute liver failure in the United States. Recognize that many cold or flu remedies also contain acetaminophen and combining these medicines with acetaminophen tablets may exceed the recommended maximum intake.

Reference: NCBI, NIH

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