The body temperature refers to the temperature of the viscera and tissues of the body. It is kept within the normal level by maintaining a balance between the heat gain and heat loss, which is regulated by the hypothalamus.
The body temperature is best recorded with a mercury thermometer which should be kept in position for about a minute. Usually, the temperature is recorded in the axilla.
The normal body temperature varies from 36 degree Celsius – 37.5 degree Celsius. There is normally a diurnal variation of 1 degree Celsius, the lowest temperature being between 2-4 am and highest in the afternoon.
Fever or pyrexia is an increase of more than 1 degree Celsius or any rise above the maximal normal temperature.
What are Different Types of Fever
It must be noted that the following types of fever association are generally noted as classic associations and overlap might occur.
The temperature remains above normal throughout the day and does not fluctuate more than 1 degree Celsius in 24 hours. This type of fever occurs in lobar pneumonia, typhoid, urinary tract infection, infective endocarditis, brucellosis, typhus etc.
The temperature remains above normal throughout the day and fluctuates more than 2 degree Celsius in 24 hours. This type of fever is usually seen in patients of typhoid infection and infective endocarditis. This type of fever is most common in practice.
The high temperature is present only for some hours in a day and returns to normal for the remaining hours. When the spike occurs daily, it is quotidian; when every alternate day, it is tertian; and when every third day, it is quartan. Intermittent fever is seen in malaria, kala-azar, pyemia, septicemia, etc.
Hectic or Septic Fever
The temperature variation between peak and nadir is very large and exceeds 5 degree Celsius. This type of fever occurs in septicemia.
Pel Ebstein Fever
In this type, there is a regular alternation of recurrent bouts of fever and afebrile periods. The temperature may take 3 days to rise, remains high for 3 days and remits in 3 days, followed by apyrexia for 9 days.
Temperature is present daily especially in the evening for several days but does not exceed 37.8 degree Celsius at any time. Usually, it does not indicate disease, but it is commonly associated with tuberculosis.
Step – Ladder fever
The stepladder is the one where the temperature rises gradually to a higher level with every spike so that new plateau is higher than preceding one, just like steps of the ladder.
Febrile episodes are separated by intervals of normal temperature. Fever, when occurs, may last for 2-9 days and then temperature gets normal. The fever may relapse after a period of few days repeating the same cycle.
It is typically seen in Borrelia infections.
Fever occurs once in 3 days or 48 hours (malaria).
Fever occurs once in four days or 72 hours (malaria due to Plasmodium malariae).
The patient gets two spikes of fever every day, generally once in the morning and once in the evening. Double quotidian may be a feature of miliary tuberculosis.
The temperature rises in the early hours of the morning rather than in the evening. It is also seen in some cases of miliary tuberculosis.
A rise in body temperature is evident in the evening hours or the patient may be woken up at night with sweating. Tuberculosis, leukemias, autoimmune disorders may have this fever.
Causes of Fever
Fever may occur whenever pyrogens are released into the body.
Any infection whether bacterial, viral, rickettsial, fungal or parasitic can give rise to fever.
Hypernephroma, lymphoproliferative malignancies, carcinoma of pancreas, lung and bone and hepatoma may cause fever.
Acute myocardial infarction, pulmonary embolism. Pontine hemorrhage may also cause fever.
A massive crush injury may lead to pyrexia.
Diseases like collagen disorders, systemic lupus erythematosus, rheumatoid arthritis, etc can lead to an increase in body temperature. Drug fever and serum sickness are can also cause fever.
Thyrotoxicosis and Addison’s disease may raise body temperature.
Fever may occur in metabolic diseases like Gout, porphyria, acidosis, dehydration, hematological conditions like an acute hemolytic crisis. Heat stroke and radiation sickness can be accompanied by fever.
Special Types of Fever
Fever with Rigors
This occurs in:
- Kala azar
- Urinary tract infection
- Infective endocarditis
Fever with Herpes Labialis
Elevated body temperature may activate the herpes simplex virus and cause small vesicles around the angle of the mouth (herpes labialis). It occurs with:
- Streptococcal infection
Fever with Rash
This is seen in:
- Chicken pox
- Small pox
Fever with Throat Membrane
- Infectious mononucleosis
- Vincent’s angina
Fever with Delirium
This is common in:
- Typhoid state
- Pneumonia (especially in alcoholics and elderly people with senility)
What is Hyperpyrexia?
Hyperpyrexia is said to occur when body temperature is more than 105 degrees Fahrenheit. It usually occurs in following conditions
- Heat Stroke
- Pontine hemorrhage
What are the Benefits of Fever
Fever is associated with the release of endogenous pyrogens, which activate the T cells and thus enhance the host defense mechanism.
Complications of Fever
Fever usually responds to medications or follows a self-limiting course. It induces a state of catabolism which is detrimental to the body. It may also lead to fluid and electrolyte imbalance-due to sweating and loss of minerals. High-grade fevers can lead to convulsions, brain damage, circulatory overload, and arrhythmia.
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