In the bi-monthly CME & Quiz series, Dr. Amdekar delivers a lesson on fever, one of the most basic medical symptoms, how it can be beneficial in disease, and when it should be controlled. 

Why does body temperature rise? 

Fever is the body’s immune response to the entry of organisms in the bloodstream or tissue damage that may result from either an infection or non-infective inflammation due to autoimmune disorders, malignancy, allergy or trauma.

Rarely, fever may result from failure of the temperature regulating system as in case of hypothalamic disorder, autonomic disturbances or heat fever and also due to increased metabolism as in case of hyperthyroidism.

Fever does not equate to infection and there are many other causes of fever. However, infection is the most common cause of fever but not necessarily a bacterial infection. Viral infections are more common, especially in healthy children. Thus, antibiotic should not be used for every fever.

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How does body temperature rise?

The body’s immune response is mediated through cytokines– chemicals produced by immune cells of the body such as monocytes/macrophages and neutrophils. These cytokines send signals to the hypothalamus that functions as a thermostat to raise body temperature to the desired set point.

Hypothalamus acts through the autonomic nervous system and regulates body temperature. If the body needs to increase temperature to a moderate degree, it is achieved by preventing heat loss by peripheral vasoconstriction that manifests as chills in the patient.

However, when the body needs to increase temperature to a much higher degree, it does so by increasing heat production by excessive muscular contractions that manifest as rigors.

One should understand that chills or rigors are not specific to any disease but simply correlate with degree and speed of rise in temperature. So malaria may not present with rigors if the parasitic load is low but typhoid fever may present with rigors if the infection is more virulent.

Takeaways:

• Degree of fever depends on the virulence of the organism and immune status of the host.
• Neonates or severely malnourished children may not present with fever in spite of serious infection
• Similarly, a child may not present with high fever to infection against which he/she is immunised
• Children staying in highly endemic areas for malaria may also not present with high fever due to partial immunity derived from repeated exposure to malarial parasites
• It is also true that absence of fever may not rule out infection

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Is fever beneficial to the body?

Fever is a friend and not a foe as it tries to prevent multiplication of organisms. Raised body temperature leads to increased blood supply to the damaged site that in turn brings in immune cells and antibodies at the site of damage.

It helps to contain the damage and promotes the healing process. Hence fever is always helpful though when such a response crosses the intended limit, it could also harm the body as it happens in hyperthermia. Fortunately, it is very rare.

Fever being an immune response is an indirect marker of good immunity or fighting power denoting nature’s attempt at healing and hence fever is a desirable response, provided it is appropriate to the given situation.

Much before science developed, it was known that serious patients with high fever often got better as against those with low fever who often succumbed. Hence in the olden days, doctors tried to induce fever hoping for a better outcome. Of course, it is no longer tenable.

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What about the risk of febrile convulsion?

Simple febrile convulsion occurs in 5% of normal children and it cannot be predicted. However, it is shortlived, for a minute and self-limiting without risk to life or resulting in brain damage.

Convulsion typically occurs within the first 24 hours of fever onset and rarely recurs in the same period of fever. Recurrence of convulsions in subsequent episodes of fever is likely and can be prevented by the prophylactic drug Clobazam.

It is important to note that the control of fever does not necessarily prevent simple febrile convulsion though it is rational to administer paracetamol in case of high fever. In fact many a time, parents notice fever only after the child develops a convulsion. Hence, there is no need to worry about febrile convulsion though recurrence can be prevented.

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Which is an ideal antipyretic?

Paracetamol is the ideal drug that controls discomfort without undue reduction of fever. It helps in diagnosis as fever pattern due to the natural progression of the disease is not altered. The earlier generation of doctors categorised fever pattern as persistent, intermittent, or remittent, that was useful in diagnosing the cause of fever.

Now, with the severe reduction of fever by 'strong' drugs, fever pattern is lost and is no longer useful for clinical diagnosis. If fever is suppressed unduly with a higher dose or more powerful antipyretic, it may lead to a false sense of disease control and one may miss the underlying condition.

Besides, it may also cause side effects. Paracetamol has an advantage over other antipyretic drugs in that it has a wide margin of safety and is devoid of gastric and renal side effects.

Paracetamol is an ideal drug that relieves discomfort caused by high fever without disturbing the body’s helpful immune response. Thereby, it helps to diagnose the cause of a fever. Besides, it is the safest antipyretic.

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What if paracetamol fails to control fever?

If paracetamol is administered much before fever attains the desired peak as per the set point in the thalamus, fever will rise in spite of the drug. This is true for every other antipyretic because once the thermostat is set at a particular point, the fever has to rise to that point.

So antipyretic is effective only when administered at the peak of fever that often coincides with significant discomfort. This fact is often ignored resulting in irrational therapy.

Children are innocent and so they are often comfortable at a moderate degree of fever. However, discomfort is a subjective feeling and should be judged on an individual basis. If paracetamol fails to achieve the desired comfort in spite of a mild reduction of fever or otherwise, it, in fact, suggests probable serious infection that calls for judicious action.

Thus it helps to diagnose serious disease in the initial stages. Another condition in which every antipyretic fails is 'central' fever – fever caused by hypothalamic dysfunction. It is a rare condition but can be suspected with a total failure of response to antipyretic.

Paracetamol rarely fails as an ideal response is to relieve discomfort and not to control fever and it does achieve the desired action. However, no antipyretic helps if administered too early in the course of a rising fever. 

In case of genuine failure, while Ibuprofen is the next alternative, provided seriousness is excluded, tepid water sponging is another temporary measure that is effective and safe. Cold compress over forehead is useless.

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How does tepid water sponge reduce body temperature?

The temperature of tepid water should be around 25ºC while body temperature in case of high fever may be around 40ºC. When towel dipped in tepid water and squeezed is applied to the skin surface and rubbed gently, heat from the skin surface is transferred smoothly to the towel due to basic physics principle of convection. It reduces the temperature of the skin surface to which the towel is applied.

This process is repeated one by one on all four limbs, chest, abdomen, back and head. The body loses 2ºC temperature with two rounds of sponging entire skin surface of the body. This method is useful when paracetamol fails to provide comfort or fever returns after paracetamol within a period of four hours.

It is important to note that one should not use cold water. Application of cold water leads to vasoconstriction and in fact heat from the body is not allowed to dissipate. Further, a child with a high fever cannot tolerate cold water application and becomes more uncomfortable.

Tepid water sponge is effective in reducing body temperature only when it is done in an ideal way. It should be reserved when paracetamol does not produce the desired action. While sponging, the child should not be exposed to wind and skin should be dried well at the end of sponging.

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In summary, fever is the body’s protective response and in fact, it helps to recover from illness. It is rarely harmful. Fever pattern and its progress help the physician diagnose the cause of fever, provided it is not suppressed by irrational therapy.

 

 

Next article deals with the clinical application of basic facts highlighted in this article with a discussion on live case scenarios, representing day-to-day problems faced by practitioners.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.