Fever (pyrexia)
See also: Pyrogen
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"Humanity has but three great enemies; fever, famine and war, and of these by far the greatest, by far the most terrible, is fever." - William Osler
- Pyrexia/Fever: adaptive response to some physiologic stress, as a result of mechanisms involving alteration of the hypothalamic set point.
- Hyperthermia: pathologic increase in body temperature not associated with an increased hypothalamic set point (often defined as 410 C or 105.80 F)
- A fever/pyrexia is often defined as a temperature of 38.30 C (100.940 F)
However, specific definitions of fever vary.
When leukocytes detect foreign bacteria & viruses they release chemicals called pyrogens ( a type of cytokine) which induce fever (pyrexia). Pyrogens circulate in the blood to reach the hypothalamus (the thermoregulatory part of the brain) and then the hypothalamus turns up the set point of body temperature.
In general, pyrexia or fever is caused by a secondary impact of infection, tissue damage, inflammation, graft rejection, malignancy and other diseases (Elumalai et al., 2012) These impacts initiate the formation of pro-inflammatory mediators or in particular cytokines (i.e. interleukin 1β,α,β, and TNF-α). This results in an increase of prostaglandin E2 (PGE2 - Prostaglandin E2) synthesis and ultimately increases the body temperature.
Videos
Fever process:
15 Non-Infection Causes of a Fever
Fever and Infection
Treating childhood fever naturally, fever childhood
How to Treat a Fever, Herbs or Pharmaceuticals?
Why Do Fevers Get Worse at Night?
Can a Fever be Good for you?
Fever vs Hyperthermia
Infectious Diseases Mimics and Fever
Articles/Studies
Mechanisms of Fever
- Peripheral thermoreceptors are located in the skin, muscles, upper airways and venous walls.
- Thermosensors are located in the anterior hypothalamus and cervical spine.
- The thermoregulatory center establishes the “set point,” and is located in the preoptic area of the hypothalamus.
- The thermoregulatory system maintains that “set point.”
- Exogenous pyrogens (such as bacterial endotoxins), stimulate inflammatory cells.
- Inflammatory cells release endogenous pyrogens (Il-1, IL-6, interferons)
- These endogenous pyrogens stimulate prostaglandins, which reach the thermoregulatory center (hypothalamus) and increase the set point.
- At higher temperatures, protective mechanisms, such as lymphocyte proliferation and antibody formation, kick in.
Fever is defensive and increases our immunity bacterial and viral infections, it accelerates the course of phagocytosis, inflammation and other defensive reactions. But every case of fever is accompanied by a decrease of iron content in the blood. That’s not good for bone marrow, or red blood cells, its very bad for hematopoiesis. If you get fevers frequently, or have a prolonged fever, it may cause iron deficiency (even iron deficient anemia).
In animal experiments it was found that giving iron to animals in fever caused the defensive effects of fever to vanish! It appears that its not the high temperature that is defensive, but the low levels of iron. It turns out that bacteria also need iron. We intentionally produce the hormone named hepcidin in the liver, to decrease absorption of iron in a fever. Also, iron is used to activate reactive oxygen species production.
So the bad side effects of a fever are the cost of our defense.
Fever can be broken down into 3 big classes:
1. Infection
2. Inflammation
3. Neoplasm
2 Classifications:
1. Based on duration:
- Acute : less than 7 days, examples, malaria, viral upper respiratory infection,
- Subacute: less than 2 weeks, examples, typhoid fever, abscess
- Chronic/ Persistent Fever, longer than 2 weeks, examples, TB, HIV, Cancers, CTD (connective tissue diseases)
2. Based on height of body temperature: low grade, moderate grade, high grade, hyperpyrexia
Extremes of temperature: Hyperpyrexia is over 106, hypothermia is less than 97
Hyperpyrexia: Usually not an infectious cause. Look for non infectious causes for such high fevers:
· Central fevers
· Drug fever
· Heat stroke
· HIV
· Malignant hyperthermia
· Malignant neuroleptic syndrome
Hypothermia
· Elderly
· Cold exposure
· Hypothyroidism
· Sepsis in chronic renal failure
· Overwhelming infection
· Overzealous treatment with antipyretics
· Hypothermia + Bacteremia = Bad Prognosis
4 Important Clues to Establish Probable Cause of Fever:
· Clinical or Lab Findings
· Appearance of Patient
· Fever Magnitude or Fever Pattern
· Abruptness of onset of Fever
Fever curves are helpful only in a few infectious diseases BUT, certain infections are regularly and reproducibly associated with a particular fever pattern.
Usefulness of fever patterns has been questioned by some in the last few decades but if a patient only has fever as the presenting sign without any localizing signs, fever pattern may be the only way to arrive at a working diagnosis. With the emergence of new diseases, fever patterns have changed.
The pattern of the rise and fall of temperature may be a clue to diagnosis. Examples, Mononucleosis, malaria, roseola, military TB. See Fever Patterns
3 Major Patterns Based on Frequency
1. Sustained/Continuous Fever
2. Intermittent Fever
3. Remittent Fever
A way to lower fever:
Bath with ice cubes of catnip/ 1/4 cup ac vinegar. Catnip enema
Crush some ginger and basil leaves together into paste, then add a teaspoon of honey. Squeeze out the liquid, and then take a drink ever four hours or so.
Flavonoids are known to target prostaglandins in the late phase of acute inflammation and pain (Chakraborty et al., 2004).
Vitamin D is beneficial in improving fever and cough resolution.