Fever (Pyrexia), its Causes, and, its Treatment.

What is Fever (Pyrexia)?

Fever (pyrexia) is the abnormal rise of body temperature due to departure from homeostasis (steady state). Fever is not a disease by itself. It is actually a rise in body temperature by the disturbance in body metabolism due to infections, excessive exercise, the body’s reaction to vaccines, and even sometimes in hot weather.

Role of the hypothalamus:

The regulation of body temperature is under the control of the hypothalamus, which is a part of the brain. It is also called the thermostat of humans, in normal conditions alteration of temperature is regulated by the hypothalamus.

For example, in cool weather when the temperature of the environment is lower than our normal body temperature, then our body temperature tends to fall. Receptors in our skin send these signals of lowering body temperature to the hypothalamus. The hypothalamus starts thermogenesis (heat production) by shivering and hormonal actions. In this way temperature of the body becomes normal.
When the weather is warm and dry, the temperature of the environment is higher than our normal body temperature and our body temperature tends to rise. Receptors in our skin send these signals of rising body temperature to the hypothalamus. The hypothalamus activates cooling strategies like sweating body temperature again becomes normal.

Pyrogens:

These are fever-causing substances produced by either pathogens or our body cells. These are the chemical agents that trigger the rise of body temperature resulting in Poyreixa (fever).

Physiology of Fever (Pyrexia):

Fever only occurs when the set point of our body temperature is disturbed due to any reason.

Does fever have some importance?

Sometimes fever is an autoimmune response of the human body, usually to cope with infectious agents. Fever of this kind is of great importance in the removal of pathogens from the body. Mostly after vaccination, our body temperature rises from the optimum value temporarily. Whether fever is good or bad, any human having hyperthermia may be very uncomfortable. These uncomfortable conditions of the human body are directly proportional to temperature. An increase in body temperature increases uneasiness.

Causes of Fever (Pyrexia):

1. Infections:

The major kind of infections results in fever is viruses (Influenza, HIV, Hepatitis), Bacteria (Tuberculosis, Typhoid,), fungi, and protozoans (Malaria). About 40 % of pyrexia results from infections.

2. Collagen diseases:

Arthritis (especially rheumatoid), systemic lupus erythematosus, polyarteritis, etc.

3. High metabolic rate:

Due to some excessive exercise and strenuous work, the body temperature also temporarily rises.

4. Stress:

This is also a cause of pyrexia, some patients show very high temperatures when subjected to stress, while others show persistent low fever during emotional and psychological stress.

5. Miscellaneous causes:

Such as the use of some drugs, ulcerative colitis, sarcoidosis, etc.

6. Unknown reasons:

About 5 – 15 % of fever is due to unknown reasons.

If you are interested to know about the pyrexia (fever) of unknown origin, click here

Types of fever (Pyrexia) on the basis of temperature:

Low fever: When the body temperature is about 100.5 – 102.2 ⁰F, this temperature is called low fever.
Moderate fever: When the body temperature is about 102.3 – 104.0 ⁰F, this temperature is called low fever.
High fever: When the body temperature is about 104.1 – 106 ⁰F, this temperature is called low fever.
Hyperpyrexia: When the body temperature is above 106 ⁰F, this temperature is called low fever. This temperature is very dangerous and at this temperature, body metabolism collapses.

Types of Fever (Pyrexia) on the basis of occurrence:

Intermittent Pyrexia:

When the temperature becomes normal at least one time in the whole 24 hours.

Reasons: Bacterial infections, abscesses, sepsis, etc.

Remittent Pyrexia:

When the temperature doesn’t become routine, instead varies a few degrees above or low from 37⁰C.

Reasons: Upper respiratory tract infections, mycoplasma infections, etc.

Continuous or sustained Pyrexia:

When the temperature is continuously above normal.

Reason: This is a drug-associated fever:

Hectic Pyrexia:

Hectic fever may be remittent or intermittent but has a difference of 1.4 ⁰C in between high and low body temperature.

Relapsing Pyrexia:

When fever occurs in the period of rhythmical or arhythmical episodes for a much longer period of time.

Reason: Malaria, TB, Fungal infections, etc.

Symptoms of pyrexia:

High temperature
Headaches
Muscular pains
Abnormality in hunger
Weakness
Sometimes feeling cold leads to chills

Note: Other symptoms are also associated with these symptoms but those are due to some other abnormalities and infections.

Pyrexia vs febrile:

Febrile is actually a medical term used as an adjective. It means things related to fever. It is also used with seizures, as febrile seizures mean convulsions as a consequence of pyrexia.

Stages of pyrexia:

Reactive phase:

The human body reacts with abnormality. This is due to pyrogens that affect the hypothalamus. In this stage, leucocytes start attacking the pathogens.

Leveling off Phase:

The second phase is in which thermogenesis becomes equal to heat loss.

Cooling Phase:

It is the last phase when the temperature becomes normal and the immune system completes its duty.

Effects of Pyrexia:

Disturbance in metabolism
General Weakness
Heat cramps
Heat exhaustion
Heatstroke
Prolonged hyperthermia leads to multi-organ failure

Treatment of Pyrexia at home:

Use cool bandages, handkerchiefs, or cloth on the forehead, back of the neck, hand, and feet to lower body temperature.
Take a bath with lukewarm water.
Drink liquid food as much as possible, and this is not too much warm or cold.
The bed must be placed in an aerated place in warm seasons.
Avoid any stuffing of blankets on you and wear loose clothes.
Use antipyretic drugs (ibuprofen, paracetamol) to lower body temperature.

Treatment at the Hospital:

Try to move to any hospital as soon as possible.
Perform diagnostic tests prescribed by physicians.
Complete medicine according to the prescription of a doctor.

References:

Golan, D. E., Armstrong, E. J., & Armstrong, A. W. (2017). Principles of pharmacology: The pathophysiologic basis of drug therapy (4th edition). Wolters Kluwer.
Papadakis, M. A., & McPhee, S. J., Rabow, M. W. (Associate editor). (2019). Current Medical Diagnosis and Treatment. (58th Edition). McGraw Hill Education.
Hammer, G. D., & McPhee, S. J. (2019). Pathophysiology of Disease: An introduction to clinical medicine. (8th edition). McGraw Hill Education.
McCance, K. L., & Huether, S. E. (2018), pathophysiology: The biological basis for disease in adults and children (8^th edition). Elsevier Health Sciences.