Fever

The normal body temperature varies from 36°C-37.5°C. There is normally a diurnal variation of 1•c, the lowest temperature being between 2-4 am and highest in the afternoon.

Fever or pyrexia is an increase of more than 1 °C or any rise above the maximal normal temperature. The following terms are used when recording the body temperature:

Celsius Fahrenheit

1.Hypothermia 35° 95°

2. Subnormal 35.0-36.7° 95-97°

3. Normal 36.7-37.2° 98-99°

4. Mild fever 37.2-37.8 99-1000

5. Moderate fever 37.8-39.46 100-103•

6. High fever 39.4-40. 103-105·

7. Hyperpyrexia >40.5° > 105•

Types of Fever

1. Continuous fever: The temperature remains above normal throughout the day and does not fluctuate more than 1 °C in 24 hours e.g. lobar pneumonia, typhoid, urinary tract infection, infective endocarditis, brucellosis, typhus, etc.

2. Remittent fever: The temperature remains above normal throughout the day and fluctuates more than 1 •c in 24 hours e.g. typhoid, infective endocarditis, etc. This type of fever is most common in practice.

3. Intermittent fever: The temperature is present only for some hours in a day and remits 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.

4. Hectic or septic: The temperature variation between peak and nadir is very large and exceeds s·c e.g. septicemia.

5. Pel Ebstein 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 seen in Hodgkin's lymphoma.

6. Low grade fever: Temperature is present daily especially in the evening for several days but does not exceed 37.8°C at any time. Usually it does not indicate disease, but it is commonly present with tuberculosis.

Causes of Fever

1. Infections: Bacterial, viral, rickettsial, fungal parasitic, etc.

2. Neoplasms: Fever may be present with any neoplasm but commonly with hypernephroma, lymphoproliferative malignancies, carcinoma of pancreas, lung and bone and hepatoma.

3. Vascular: Acute myocardial infarction, puhnonary embolism, pontine hemorrhage, etc.

4. Traumatic: Crush injury.

5. Immunological:

a. Collagen disease, SLE, rheumatoid arthritis.

b. Drug fever

c. Serum sickness

6. Endocrine: Thyrotoxicosis, Addison's disease.

7. Metabolic: Gout, porphyria, acidosis, dehydration

8. Hematological: Acute hemolytic crisis

9. Physical agents: Heat stroke, radiation sickness.

10. Miscel laneous: Factitious fe ver, habitual hyperpyrexia, cyclic neutropenia

Special Types of Fever

Fever with rigors: This occurs in:

a. Malaria

b. Kala azar

c. Filariasis

d. Urinary tract infection, pyelonephritis

e. Cholangitis

f. Septicemia

g. Infective endocarditis

h. Abscesses, any site

i. Lubar pneumonia

2. 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:

a. Pneumonia

b. Malaria

c. Meningitis

d. Severe streptococcal infection

3. Fever with rash: This is seen in:

a. Chicken pox

b. Small pox

c. Measles

d. Rubella

e. Typhus

g. Allergy

4. Fever with membrane in the throat: Occurs in:

a. Diphtheria

b. Infectious mononucleosis

C. Agranulocytosis

d. Moniliasis

e. Vincent's angina.

5. Fever with delirium: This is common in:

a. Encephalitis

b. Typhoid state

c. Meningitis

e. Pneumonia ( especially in alcoholics and elderly

people with dementia)

f. Hepatic encephalopathy

6. PUO (Pyrexia of Unknown Origin)

a. Temperature > 101 °F (38.3°C) on several occasions.

b. Duration >3 weeks

c. Duration > l week in hospital with failure to reach diagnosis.

Classification

a. Classical PUO (lymphoma, collagen vascular disease, abscess, TB, viral infection, endocarditis)

b. Nosocomial PUO: hospitalized, no fever on admission (thrombophlebitis, catheter infections, deep vein thrombosis, drug fever, transfusion reaction)

c. Neutropenic PUO: Absolute neurophil count <500 (fungal infection, perianal infection)

d. PUO in HIV infection (TB, Pneumocystisj iroveci, toxoplasma, cryptococcus, CMV, Non Hodgkins Lymphoma).

Hyperpyrexia

Hyperpyrexia is said to occur when body temperature

is more than 10s·F.

Causes

1. Tetanus

2. Malaria

3. Septicemia

4. Heat Stroke

5. Encephalitis

6. Pontine hemorrhage

7. Neuroleptic malignant syndrome

Benefits of Fever

In some human diseases, fever is beneficial, e.g. wide· spread cancer, neurosyphilis, chronic arthritis, etc. Fever was often induced in these diseases by injection of milk protein or BCG vaccine. It has been suggested that fever is associated with release of endogenous pyrogens, which activate the T cells and thus enhance the host defense mechanism.

Harmful Effects

l. Hypercatabolism-nitrogen wastage and weight loss.

2. Fluid and electrolyte imbalance· due to sweating.

3. Convulsions and brain damage

4. Circulatory overload, arrhythmias, etc.

Hypothermia

Hypothermia is decreased body temperature.

Causes

l. Endocrine: Hypothyroidism or myxedema, hypopit ui t a r i s m (Si m m o n d s c a c h exia), hypoglycemia

2. Toxic: Alcoholic intoxication, barbiturate

poisoning, ketoacidosis

3. Exposure to cold

4. Autonomic dysfunction or dysautonomias