Human Body Temperature

• Normal human body temperature, also known as normothermia or euthermia, depends on the measurement location, time of day, and activity level.
• A healthy person's body temperature varies by about 0.5°C (0.9°F) during the day, with lower temperatures in the morning and higher temperatures in the late afternoon and evening.
• Generally accepted normal body temperature is 36.8° ± 0.5°C
• Temperatures can be measured rectally, vaginally, in the ear (Otic), orally or axillary.
• Rectal, vaginal, or ear measurements: temp °C - 0.5 °C
• Oral measurements: temp without any addition
• Axillary measurements: temp °C + 0.5 °C

Temperature Classifications

• Hypothermia is defined as a temperature less than 35.0°C.
• Normal temperature is defined as a temperature between 36.5-37.5°C
• Fever is defined as a temperature between 37.3-38.3°C.
• Hyperthermia is defined as a temperature between 38.3-40.0°C.
• Hyperpyrexia is defined as a temperature over 40.0-41.5°C.

Hypothermia

• Hypothermia is usually due to excessive exposure to cold air or water
• Symptoms usually appear when the body's core temperature drops by 1-2° below normal.

Fever

• A temperature set-point is the level at which the body attempts to maintain its temperature.
• When the set-point is raised, it results in a fever.
• Most fevers are caused by infectious diseases.
• Fevers can be lowered with antipyretic medications.
• An early morning temperature higher than 37.2°C (>98.9°F) or a late afternoon temperature higher than 37.7°C (>99.9°F) is normally considered a fever.
• Normal daily temperature variation is typically 0.5°C (0.9°F), but can be greater among people recovering from a fever.

Hyperpyrexia

• Hyperpyrexia is usually caused by prolonged exposure to high temperatures.
• Hyperpyrexia at or above about 40°C (104°F) is a life-threatening medical emergency treated immediately.
• Common symptoms include headache, confusion, fatigue.
• Dehydration from sweating may result in dry, red skin.

Causes of Fever

• Infection (e.g., tonsillitis)
• Malignant tumor
• Extreme sunburn
• Some immunizations, such as the diphtheria, tetanus, and acellular pertussis (DTaP) or pneumococcal vaccine
• Some medications, such as antibiotics

Diagnosis of Fever

• Diagnosing a fever means diagnosing the infection causing it.
• Investigations are guided by clinical examination and duration of fever.
• Examinations may include blood, urine, sputum, stool, cultures, serological tests, x-ray, ultrasound, etc.

Examinations

• Blood examination, like Complete blood counts including Hb, ESR, can give vital information including type and severity of infection.
• Sputum examination in cases of pneumonia and bronchitis to isolate organisms causing chest infection.
• Urine examination includes microscopic analysis and culture for diagnosing UTI (Urinary tract infection).
• Stool examination helps diagnose dysentery, cholera, etc.
• Cultures, if positive, give confirmatory evidence of infection by a particular organism and provide a list of effective antibiotics; cultures of blood, sputum, throat swab, pus, urine, and stool can be done
• X-ray can diagnose chest infection, sinusitis, tuberculosis, and bone infection.

Clinical Presentation of Fever

• Feeling hot
• Headache
• Rapid heart rate and/or palpitation
• Intermittent sweats
• Shivering, shaking, chills
• Aching muscles and joints
• Loss of appetite
• Feeling faint or dizzy
• High fevers between 39.4°C and 41.1°C can cause Hallucinations, Confusion, Irritability, Convulsions, and Dehydration

Treatment

• Treatment is according to the cause of the fever.