ज्वर (वापाइरेक्सिया') छगू आपालं खनिगुचिकित्सिकलक्षण ख। थ्व लक्षणंम्हया तापक्रम साधारण (साधारण म्हुतुइ दैगुसाधारण मनुया म्ह तापक्रम ३६॰८±०.७ °से॰ वा ९८.२±१॰३ °फ) स्वया अप्वगु जानकारी बी। Fever is most accurately characterized as a temporary elevation in the body's thermoregulatory set-point, usually by about 1–2°C. Fever differs fromhyperthermia, which is an increase in body temperature over the body's thermoregulatory set-point (due to excessive heat production or insufficientthermoregulation, or both).Carl Wunderlich discovered that fever is not a disease but a symptom of disease.
The elevation in thermoregulatory set-point means that the previous "normal body temperature" is consideredhypothermic, and effector mechanisms kick in. The person who is developing the fever has a cold sensation, and an increase inheart rate,muscle tone andshivering attempt to counteract the perceivedhypothermia, thereby reaching the new thermoregulatory set-point.
When a patient has or is suspected of having a fever, that person's body temperature is measured using a thermometer. At a first glance, fever is present if:
temperature in the anus (rectum/rectal) or in the ear (otic) is at or over 38.0°C (100.4°F)
temperature in the mouth (oral) is at or over 37.5°C (99.5°F)
temperature under the arm (axillary) is at or over 37.2°C (99.0°F)
However, there are many variations in normal body temperature, and this needs to be considered when measuring fever. The values given are for an otherwise healthy, non-fasting adult, dressed comfortably, indoors, in a room that is kept at a normal room temperature, during the morning, but not shortly after arising from sleep. Furthermore, for oral temperatures, the subject must not have eaten, drunk, or smoked anything in at least the previous fifteen minutes.
Body temperature normally fluctuates over the day, with the lowest levels at 4 a.m. and the highest at 6 p.m. Therefore, an oral temperature of 37.5°C (99.5°F) would strictly be a fever in the morning, but not in the afternoon. Normal body temperature may differ as much as 0.4°C (0.7°F) between individuals or from day to day. In women, temperature differs at various points in themenstrual cycle, and this can be used forfamily planning (although it is only one of the variables of temperature). Temperature is increased after meals, and psychological factors (like the first day in the hospital) also influence body temperature.
There are different locations where temperature can be measured, and these differ in temperature variability.Tympanic membranethermometers measure radiant heat energy from the tympanic membrane (infrared). These may be very convenient, but may also show more variability.
Children develop higher temperatures with activities like playing, but this is not fever because their set-point is normal. Elderly patients may have a decreased ability to generate body heat during a fever, so even a low-grade fever can have serious underlying causes ingeriatrics.
Temperature is regulated in thehypothalamus, in response toPGE2. PGE2 release, in turn, comes from a trigger, a pyrogen. The hypothalamus generates a response back to the rest of the body, making it increase the temperature set-point.
Hyperthermia: Characterized on the left. Normal body temperature (thermoregulatory set-point) is shown in green, while the hyperthermic temperature is shown in red. As can be seen, hyperthermia can be conceptualized as an increase above the thermoregulatory set-point. Hypothermia: Characterized in the center: Normal body temperature is shown in green, while the hypothermic temperature is shown in blue. As can be seen, hypothermia can be conceptualized as a decrease below the thermoregulatory set-point. Fever: Characterized on the right: Normal body temperature is shown in green. It reads "New Normal" because the thermoregulatory set-point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic.
These cytokine factors are released into general circulation where they migrate to the circumventricularorgans of thebrain, where theblood-brain barrier is reduced. The cytokine factors bind withendothelial receptors on vessel walls, or interact with localmicroglial cells. When these cytokine factors bind, they activate thearachidonic acid pathway.
One model for the mechanism of fever caused by exogenous pyrogens includes LPS, which is a cell wall component ofgram-negative bacteria. An immunological protein calledlipopolysaccharide-binding protein (LBP) binds to LPS. The LBP–LPS complex then binds to theCD14 receptor of a nearbymacrophage. This binding results in the synthesis and release of various endogenouscytokine factors, such as interleukin 1 (IL-1), interleukin 6 (IL-6), and the tumor necrosis factor-alpha. In other words, exogenous factors cause release of endogenous factors, which, in turn, activate the arachidonic acid pathway.
PGE2 is the ultimate mediator of the febrile response. The set-point temperature of the body will remain elevated until PGE2 is no longer present. PGE2 acts on neurons in thepreoptic area (POA) through the EP3 subtype of PGE receptors and the EP3-expressing neurons in the POA innervate thedorsomedial hypothalamus (DMH), the rostralraphe pallidus nucleus in themedulla oblongata (rRPa) and theparaventricular nucleus of thehypothalamus (PVN). Fever signals sent to the DMH and rRPa lead to stimulation of thesympathetic output system, which evokes non-shivering thermogenesis to produce body heat and skin vasoconstriction to decrease heat loss from the body surface. It is presumed that the innervation from the POA to the PVN mediates the neuroendocrine effects of fever through the pathway involvingpituitary gland and variousendocrine organs.
Theautonomic nervous system may also activatebrown adipose tissue to produce heat (non-exercise-associatedthermogenesis, also known as non-shivering thermogenesis), but this seems mostly important for babies. Increased heart rate and vasoconstriction contribute to increasedblood pressure in fever.
The last is amedical emergency because it approaches the upper limit compatible with human life.
Most of the time, fever types can not be used to find the underlying cause. However, there are specific fever patterns that may occasionally hint thediagnosis:
Pel-Ebstein fever: a specific kind of fever associated withHodgkin's lymphoma, being high for one week and low for the next week and so on. However, there is some debate as to whether this pattern truly exists.[१]
Intermittent fever: temperature is present only for some hours of the day and becomes normal for remaining hours, e.g.malaria,kala-azar,pyaemia, orsepticemia. In malaria, there may be a fever with a periodicity of 24 hours (quotidian), 48 hours (tertian fever), or 72 hours (quartan fever, indicatingPlasmodium vivax). These patterns may be less clear in travelers.
Remittent fever: temperature remains above normal throughout the day and fluctuates more than 1°C in 24 hours, e.g.infective endocarditis.
Febricula[२] is a mild fever of short duration, of indefinite origin, and without any distinctive pathology.
There are arguments for and against the usefulness of fever, and the issue is controversial.[३][४] There are studies usingwarm-bloodedvertebrates[५] andhumans[६]in vivo, with some suggesting that they recover more rapidly from infections or critical illness due to fever.
Theoretically, fever has been conserved during evolution because of its advantage for host defense.[३] There are certainly some important immunological reactions that are sped up by temperature, and somepathogens with strict temperature preferences could be hindered.[७] The overall conclusion seems to be that both aggressive treatment of fever[६] and too little fever control[३] can be detrimental. This depends on the clinical situation, so careful assessment is needed.
Fevers may be useful to some extent since they allow the body to reach high temperatures. This causes an unbearable environment for some pathogens. White blood cells also rapidly proliferate due to the suitable environment and can also help fight off the harmful pathogens and microbes that invaded the body.
Fever should not necessarily be treated. Fever is an important signal that there's something wrong in the body, and it can be used for follow-up. Moreover, not all fevers are of infectious origin.
Even when treatment is not indicated, however, febrile patients are generally advised to keep themselves adequately hydrated, as thedehydration produced by a mild fever can be more dangerous than the fever itself. Water is generally used for this purpose, but there is always a small risk ofhyponatremia if the patient drinks too much water. For this reason, some patients drinksports drinks or products designed specifically for this purpose.
Most people take medication against fever because the symptoms cause discomfort. Fever increasesheart rate andmetabolism, thus potentially putting an additional strain on elderly patients, patients withheart disease, etc. This may even causedelirium. Therefore, potential benefits must be weighed against risks in these patients. In any case, fever must be brought under control in instances when fever escalates tohyperpyrexia and tissue damage is imminent.
Treatment of fever should be based primarily on lowering the set-point, but facilitating heat loss may also contribute. The former is accomplished withantipyretics. Wet cloth or pads are also used for treatment, and applied to the forehead. Heat loss may be an effect of (possibly a combination of)heat conduction,convection,radiation, orevaporation (sweating, perspiration). This may be particularly important in babies, where drugs should be avoided. However, ifwater that is too cold is used, it inducesvasoconstriction and prevents adequate heat loss.
123Schaffner A. Fever—useful or noxious symptom that should be treated?Ther Umsch 2006;63: 185-8.PMID 16613288
↑Soszynski D. The pathogenesis and the adaptive value of fever.Postepy Hig Med Dosw 2003;57: 531-54.PMID 14737969
↑Su, F.; Nguyen, N.D.; Wang, Z.; Cai, Y.; Rogiers, P.; Vincent, J.L. Fever control in septic shock: beneficial or harmful?Shock 2005;23: 516-20.PMID 15897803
12Schulman, C.I.; Namias, N.; Doherty, J., et al. The effect of antipyretic therapy upon outcomes in critically ill patients: a randomized, prospective study.Surg Infect (Larchmt) 2005;6:369-75.PMID 16433601
↑Fischler, M.P.; Reinhart, W.H. Fever: friend or enemy?Schweiz Med Wochenschr 1997;127: 864-70.PMID 9289813
Rhoades, R. and Pflanzer, R. Human physiology, third edition, chapter 27Regulation of body temperature, p. 820Clinical focus: pathogenesis of fever.ISBN 0-03-005159-2
