Fever Definition And All


Unbalanced body normal temperature

  • Body temperature above 99oF (37.2o) called fever or pyrexia.
  • Fever is not a disease but a sign of a disease.



  • Infection & malignancy.
  • Heat stroke & dehydration.
  • Crushing injury & surgical trauma.
  • Allergic reaction.


Onset or invasion– -Fever start and increase.

Fastigium or stadium – Body temperature at maximum & constant level.

Defervescence or decline– Sudden and fast (crisis) or slowly (lysis) decreasing temperature to become normal.

Crisis– Fastly decreasing body temperature.-

  • True crisis-patient condition also improves with decreasing temperature.
  • False crisis -Without improving the condition of patient temperature decrease suddenly.

Lysis-Slowly fever becomes normal.


Constant or continuous– A sustained fever, with a slight diurnal variation (less than 2°C or 3.6oF) as in scarlet fever, typhus or pneumonia.

Remittent – A pattern of fever that varies over a 24-hour period (difference more than 2oC  in evening and morning temperature) but does not return to normal.

Intermittent  (quotidian)-

  • Temperature rises from normal or subnormal to high & back at regular interval higher temperature in evening and lower in morning).
  • A Fever in which symptoms disappear completely between paroxysms (an exacerbation of the symptoms of a disease).

Inverse – Highest temperature in morning & lowest in evening.

Hectic or swinging  – Difference between high & low temperature is very high

Relapsing – Normal temperature for one or two days after a brief period.

Irregular –  Fever is completely irregular, so cannot classify into any group of fever mentioned above.

Fever of unknown origin (FUO) – An illness of at least 3 weeks duration with  exceeding 38.3°C  on

several occasions and diagnosis not established after 1 week of hospital investigation.


  • Fever occurs by resetting of temperature  regulating center of hypothalamus at a higher level (higher than 98.6oF) by the release of interleukin-1 (IL-1), interleukin-2(IL-2) and tumor necrosis factor from white blood cells (especially macrophages)
  • Then the body tries to maintain that resetting higher temperature level.

Grade of fever or pyrexia

  • Low pyrexia – 99o to 100oF (37.2o-37.8o C).
  • Moderate pyrexia – 100o to 103oF (37.8°- 39.4c).
  • High pyrexi a– 103° to 105F (39.4°-40.6oc).
  • Hyperpyrexia & hyperthermia-Temperature above 105oF.
  • Subnormal temperature– 95 to 98o F (35o– 36o C) or below normal.
  • Hypothermia-Temperature below  95oF or 35oC.
  • Mild hypothermia -90 to 95o
  • Moderate hypothermia- 86o to 90o
  • Severe hypothermia – Below 86o


A sudden paroxysmal shaking chill occurring during a febrile illness e,g malaria.

Respiratory alkalosis may occur in shivering due to hyperventilation.

Stages of rigor

(i) Cold Stage (the chill or rigor stage)-

  • Uncontrolled shivering and tachycardia occur in this stage.
  • Body feels cool and temperature rises to 103’F or more.
  • Cover the patient with warm blankets and give warm drinks.

(ii) Hot Stage (febrile stage)

  • Stop Shivering and patient become hot, dry, restlessness & thirsty.
  • Temperature increasing continuously.
  • Remove all blankets and give cold drinks & cold compression.
  • Temperature increase up to and above 105F.
  • Start cold sponging.

(iii )Sweating Stage (the third or terminal stage during which sweating occurs)-


  • It is a dangerous stage, because patient may go in shock if not cared properly.
  • Excessive diaphoresis with decreasing temperature and improving pulse of patient.
  • Dry up the patient.



Care During Fever

  • Give sweet drinks to treat fatigue.
  • Temperature should be recorded at 10-15 minute interval in rigor.
  • Neurogenic fever not responds to antipyretic drugs, so manage with cold therapy.
  • Maintain body temperature.
  • Satisfy nutritional needs of patient because O2, consumption or nutritional requirements increase 13% at 1oc or 7% at 1of  temperature elevation.
  • So give high-calorie diet & fluid (3000ml/day) to balance fluidIoss.
  • Provide rest & sleep, maintain personal hygiene, provide safety and observe patient carefully.
  • give medication like paracetamol and antibiotics to increase immunity level

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