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Fevers: friend or foe?


"You give me fever when youkiss me, fever when you hold me tight.' When Peggy Lee sang those words in the 1950s, she was referring to the "heat' of passion, to "burning' desire. But what is the real physiological reaction called "fever'? Where does it come from and what is it good for?

Ancient History

The ancients noticed that althoughman and some animals remained warm, reptiles, amphibians, and fish seemed to attain only the temperature of their environment. Early philosophers concentrated on explaining why man was warm, why breath was warm even when the air inhaled was cold, why blood was warm even when the person felt cold. Because the only source of heat was fire, it was assumed that somewhere in the body a fire burned.

In early history, the location ofthe fire was thought to be the heart. But nobody knew just how the heart worked. In the second century A.D., the Greek physician Galen, drawing on ideas of earlier philosophers such as Plato and Hippocrates, concluded the function of the heart was to mix blood with inhaled air. This mixture created an incandescence, a biological flame, which heated both the blood and the air.

The ancients also deduced thatwhen a body became ill, this flame burned brighter, causing more heat, which could be seen and felt on the skin as fever. Illness was supposedly caused by an imbalance of four body humors, which corresponded to an even older belief that all matter is composed of four elements: earth, air, fire, and water. In the body, these elements became blood, phlegm, yellow bile, and black bile. As the fire in the heart increased, it cooked the offending humor. Fever also aided the removal of humors by inducing combinations of vomiting, diarrhea, and sweating. The purpose of fever, Greek physicians believed, was to restore the natural balance of humors and to eliminate illness.

The concept of fever as a hotterfire in the heart persisted until the Renaissance. Anatomists then proved there was no mixing of fire with humors, no residue of fire, and, ultimately, no fire in the heart. However, the purpose of fever remained unchallenged until the late 1700s, when many physicians became convinced humors didn't account for disease states. The explosion of medical and physiological discoveries in the 1700s and 1800s identified causes of fever. Carl Leibermeister, a German physician in the late 1800s, was the first to redefine fever as a resetting of the body's natural heat to a higher temperature. The fever-reducing medications of the 20th century have given us a chemical means to study the source and purpose of fever more accurately.

The Body's Thermostat

How does the body control itstemperature? In the past several decades, we have learned about a place in the brain, the hypothalamus, called the body's metronome because it controls both breathing and heartbeat. The hypothalamus is also responsible for controlling body temperature.

To conserve heat when we arecold, the hypothalamus keeps blood from the skin by contraction of the small blood vessels on the body surface and in the skin, a process called vasoconstriction. If this isn't enough, we shiver. Shivering is a very weak and rapid contraction of skeletal muscles, which produces internal heat to warm the body core. The skin looks pale and white when we are cold.

To lose heat the hypothalamussends blood to the surface of the skin by opening the same small vessels, a process called vasodilatation. Heat is radiated away, and thus cooling of the body core ensues. If we are still too hot, we perspire to add evaporative cooling to the effort. The skin becomes flushed and pink.

We also have behavioral actionsto help change our temperature. If cold, we curl up in a ball, put on more clothes, seek out warmth. If hot, we take off clothes, immerse ourselves in cool water, drink cool liquids. All these actions are done instinctively to attempt to keep our body temperature at its normal 35.5|C. to 37.5|C. (97.7|F. to 99.5|F.).

We now know that when webecome ill a sequence of events leads to a change in the "set point' of the body's thermostat. Our white blood cells produce and release a small protein called EP-- endogenous pyrogen (literally, "inside-the-body fire maker'). This protein acts indirectly on the hypothalamus to reset the thermostat at a higher temperature. Chemicals called prostaglandins are released and act in concert with EP. Some infections make toxins that also serve to reset the hypothalamus.

Although we know EP (the firemaker) and prostaglandins increase temperatures, they don't cause all fevers. They can't account for fever that comes and goes for many days and weeks for no obvious reason. EP and prostaglandins haven't been proved responsible for the occasional fever related to cancer. They also don't explain why fever rarely goes above 41|C. (105.8|F.). It isn't known how fire makers interact with cryogens ("cold makers') to restore the thermostat to its normal level. We just know that the system works.

Some Good from Ill

O.K., so there are a lot of waysto get a fever. So what? It still makes us feel lousy. What good does it do? The verdict is still out, but we have learned some amazing things. We know now that even cold-blooded animals get fevers. How can this be when they can't even muster enough heat to keep their bodies warmer than the air around them?

Persistent investigation hasanswered that question. We know that lower animals have a hypothalamus that controls the temperature at which the body is comfortable. When an iguana gets infected, for instance, its hypothalamus is reset to a higher level, just as in a human. Because the iguana can't generate enough internal heat to reach this new level, how then does it show its fever? Researchers have discovered that an infected iguana seeks out warmer areas in its environment. It uses behavioral techniques to achieve the higher temperature--it develops a "behavioral fever.' The studies, repeated for reptiles, amphibians, and fish, show the same results in each case: the creation of behavioral fevers.

Experiments have also shownthat lower animals and higher animals demonstrate very similar febrile responses--too many to be coincidence. As examples, fevers in lower and higher animals develop secondarily to the same stimuli; both groups have very similar fire makers (pyrogens); fever-reducing drugs work equally well on both groups. Because reptiles and mammals have existed as separate groups for at least 200 million years, these similarities suggest that the body reactions which produce fever must be even older. The fever response has been around and stayed around for a long time.

Because reptiles' reactions aresimilar to man's, we are able to use them to study fever. This has allowed us to learn that fever has some benefit to us. For example, if we prevent fever in response to infection, we find that 75 percent of infected reptiles die. If we allow the fever to exist, only 25 percent die. Fever allows our natural defenses to be more efficient. White blood cells are more mobile and more aggressive killers of infecting organisms. Other elements of our immune system work better at high temperatures, and even interferon, our body's natural antiviral and antitumor drug, works better at elevated temperatures.

How to Treat Fever

If preventing the febrile responsein animals causes three times more deaths, there are some obvious questions we should ask about preventing it in man. When should we treat fever? How high need the temperature rise before we worry? Are we, in fact, interfering with our natural infection fighters when we reduce temperature? Unfortunately, these questions have no good answers. We do know that prolonged high temperatures in man can cause degeneration of cells in all organs, and if enough cells are killed the person may die. It would seem advantageous, therefore, to treat temperatures at or above 41|C. (105.8|F.). But what about fever less than 40|C. (105.8|F.) in an adult or sick child? What about low-grade fever for many days? The best course is to consult your family physician in these cases.

Before that consultation thereare a few guidelines to follow, however. Fever is usually a symptom of some other problem. The nature of the fever will help identify the disorder. But if you obviously have a cold and your temperature is 38.5|C. (101.3|F.), it may not be a good idea to take medicine to lower the temperature.

Never give aspirin to childrenwith a fever and signs of chicken pox or influenza unless it is recommended by a physician. Doing so carries a risk of the child's contracting Reye's syndrome, a debilitating and sometimes fatal complication.

Under no circumstances use anice bath or even cold water to lower moderate fevers in an adult or, especially, in a child. (The temperature difference between the child and the ice is so great that the body thinks it's cold, makes goose bumps, and begins to shiver. These two actions cause the real body temperature to go up, not down!)

Because fever causes water lossand burns up calories (energy), always be sure to drink plenty of fluids and eat as well as you can.

Most important, if the fevera) persists after several days, b) stays above 39.5|C. (103.1|F.), or c) causes convulsions, consult your physician about what to do next.

Research has shown us some ofthe ways we get fevers. We have seen some of the effects of fever on behavior. There is a biological value to fever, but we don't know exactly what or why. Additional research is needed to learn more about fever. But scientists needn't apologize for unanswered questions. After all, poets and philosophers are still at a loss to explain why some people get "fever in the morning, fever all through the night.'

Photo: The ancients deduced that inside thebody a fire burned and that when a person became ill, this fire burned brighter, causing heat--which could be seen and felt on the skin as fever.

Photo: Taking aspirin to lower fever from a cold or using an ice bath to reduce a moderate temperature is not a good idea. Instead, drink plenty of fluids and eat well to help counter water loss and calorie depletion.

Photo: When we are cold, warm blood is kept from the skin by the contraction of small blood vessels. If this doesn't do the trick, we produce internal heat by shivering. When we're hot, the small blood vessels dilate; the next step is perspiration.
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Author:Haley, Jim
Publication:Saturday Evening Post
Date:Mar 1, 1987
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