[Fever Download 1080p Movie
Christel Malden
Body temperatures vary slightly from person to person and at different times of day. The average temperature has traditionally been defined as 98.6 F (37 C). A temperature taken using a mouth thermometer (oral temperature) that's 100 F (37.8 C) or higher is generally considered to be a fever.
Oral and rectal thermometers generally provide the most accurate measurement of core body temperature. Ear or forehead thermometers, although convenient, provide less accurate temperature measurements.
There's probably no cause for alarm if your child has a fever but is responsive. This means your child makes eye contact with you and responds to your facial expressions and to your voice. Your child may also be drinking fluids and playing.
When your immune system responds to disease, the hypothalamus can set your body temperature higher. This prompts complex processes that produce more heat and restrict heat loss. The shivering you might experience is one way the body produces heat. When you wrap up in a blanket because you feel chilled, you are helping your body retain heat.
Children between the ages of 6 months and 5 years are at increased risk of a seizure that occurs during a fever (febrile seizure). About a third of the children who have one febrile seizure will have another one, most commonly within the next 12 months.
A febrile seizure may involve loss of consciousness, shaking of limbs on both sides of the body, eyes rolling back or body stiffness. Although alarming for parents, the vast majority of febrile seizures cause no lasting effects.
Fever or pyrexia in humans is a body temperature above the normal range due to an increase in the body's temperature set point in the hypothalamus.[5][6][12][7] There is no single agreed-upon upper limit for normal temperature: sources use values ranging between 37.2 and 38.3 C (99.0 and 100.9 F) in humans.[1][7][8] The increase in set point triggers increased muscle contractions and causes a feeling of cold or chills.[2] This results in greater heat production and efforts to conserve heat.[3] When the set point temperature returns to normal, a person feels hot, becomes flushed, and may begin to sweat.[3] Rarely a fever may trigger a febrile seizure, with this being more common in young children.[4] Fevers do not typically go higher than 41 to 42 C (106 to 108 F).[6]
Treatment to reduce fever is generally not required.[2][9] Treatment of associated pain and inflammation, however, may be useful and help a person rest.[9] Medications such as ibuprofen or paracetamol (acetaminophen) may help with this as well as lower temperature.[9][10] Children younger than three months require medical attention, as might people with serious medical problems such as a compromised immune system or people with other symptoms.[16] Hyperthermia requires treatment.[2]
Fever is one of the most common medical signs.[2] It is part of about 30% of healthcare visits by children[2] and occurs in up to 75% of adults who are seriously sick.[11] While fever evolved as a defense mechanism, treating a fever does not appear to improve or worsen outcomes.[17][18][19] Fever is often viewed with greater concern by parents and healthcare professionals than is usually deserved, a phenomenon known as "fever phobia."[2][20]
A fever is usually accompanied by sickness behavior, which consists of lethargy, depression, loss of appetite, sleepiness, hyperalgesia, dehydration,[21][22] and the inability to concentrate. Sleeping with a fever can often cause intense or confusing nightmares, commonly called "fever dreams".[23] Mild to severe delirium (which can also cause hallucinations) may also present itself during high fevers.[24]
A range for normal temperatures has been found.[8] Central temperatures, such as rectal temperatures, are more accurate than peripheral temperatures.[30]Fever is generally agreed to be present if the elevated temperature[31] is caused by a raised set point and:
Persistent fever that cannot be explained after repeated routine clinical inquiries is called fever of unknown origin.[7][54] A neutropenic fever, also called febrile neutropenia, is a fever in the absence of normal immune system function.[55] Because of the lack of infection-fighting neutrophils, a bacterial infection can spread rapidly; this fever is, therefore, usually considered to require urgent medical attention.[56] This kind of fever is more commonly seen in people receiving immune-suppressing chemotherapy than in apparently healthy people.[55][57]
Fever is thought to contribute to host defense,[17] as the reproduction of pathogens with strict temperature requirements can be hindered, and the rates of some important immunological reactions are increased by temperature.[77] Fever has been described in teaching texts as assisting the healing process in various ways, including:
A fever response to an infectious disease is generally regarded as protective, whereas fever in non-infections may be maladaptive.[80][81] Studies have not been consistent on whether treating fever generally worsens or improves mortality risk.[82] Benefits or harms may depend on the type of infection, health status of the patient and other factors.[80] Studies using warm-blooded vertebrates suggest that they recover more rapidly from infections or critical illness due to fever.[83] In sepsis, fever is associated with reduced mortality.[84]
Temperature is regulated in the hypothalamus. The trigger of a fever, called a pyrogen, results in the release of prostaglandin E2 (PGE2). PGE2 in turn acts on the hypothalamus, which creates a systemic response in the body, causing heat-generating effects to match a new higher temperature set point. There are four receptors in which PGE2 can bind (EP1-4), with a previous study showing the EP3 subtype is what mediates the fever response.[85] Hence, the hypothalamus can be seen as working like a thermostat.[7] When the set point is raised, the body increases its temperature through both active generation of heat and retention of heat. Peripheral vasoconstriction both reduces heat loss through the skin and causes the person to feel cold. Norepinephrine increases thermogenesis in brown adipose tissue, and muscle contraction through shivering raises the metabolic rate.[86]
If these measures are insufficient to make the blood temperature in the brain match the new set point in the hypothalamus, the brain orchestrates heat effector mechanisms via the autonomic nervous system or primary motor center for shivering. These may be:[citation needed]
This contrasts with hyperthermia, in which the normal setting remains, and the body overheats through undesirable retention of excess heat or over-production of heat. Hyperthermia is usually the result of an excessively hot environment (heat stroke) or an adverse reaction to drugs. Fever can be differentiated from hyperthermia by the circumstances surrounding it and its response to anti-pyretic medications.[7][verification needed]
In infants, the autonomic nervous system may also activate brown adipose tissue to produce heat (non-exercise-associated thermogenesis, also known as non-shivering thermogenesis).[citation needed]
A pyrogen is a substance that induces fever.[87] In the presence of an infectious agent, such as bacteria, viruses, viroids, etc., the immune response of the body is to inhibit their growth and eliminate them. The most common pyrogens are endotoxins, which are lipopolysaccharides (LPS) produced by Gram-negative bacteria such as E. coli. But pyrogens include non-endotoxic substances (derived from microorganisms other than gram-negative-bacteria or from chemical substances) as well.[88] The types of pyrogens include internal (endogenous) and external (exogenous) to the body.[citation needed]
Endogenous pyrogens are cytokines released from monocytes (which are part of the immune system).[90] In general, they stimulate chemical responses, often in the presence of an antigen, leading to a fever. Whilst they can be a product of external factors like exogenous pyrogens, they can also be induced by internal factors like damage associated molecular patterns such as cases like rheumatoid arthritis or lupus.[91]
Of these, IL-1β, TNF, and IL-6 are able to raise the temperature setpoint of an organism and cause fever. These proteins produce a cyclooxygenase which induces the hypothalamic production of PGE2 which then stimulates the release of neurotransmitters such as cyclic adenosine monophosphate and increases body temperature.[95]
Exogenous pyrogens are external to the body and are of microbial origin. In general, these pyrogens, including bacterial cell wall products, may act on Toll-like receptors in the hypothalamus and elevate the thermoregulatory setpoint.[96]
PGE2 release comes from the arachidonic acid pathway. This pathway (as it relates to fever), is mediated by the enzymes phospholipase A2 (PLA2), cyclooxygenase-2 (COX-2), and prostaglandin E2 synthase. These enzymes ultimately mediate the synthesis and release of PGE2.[citation needed]
PGE2 is the ultimate mediator of the febrile response. The setpoint temperature of the body will remain elevated until PGE2 is no longer present. PGE2 acts on neurons in the preoptic area (POA) through the prostaglandin E receptor 3 (EP3). EP3-expressing neurons in the POA innervate the dorsomedial hypothalamus (DMH), the rostral raphe pallidus nucleus in the medulla oblongata (rRPa), and the paraventricular nucleus (PVN) of the hypothalamus. Fever signals sent to the DMH and rRPa lead to stimulation of the sympathetic 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 involving pituitary gland and various endocrine organs.[citation needed]
Fever does not necessarily need to be treated,[98] and most people with a fever recover without specific medical attention.[99] Although it is unpleasant, fever rarely rises to a dangerous level even if untreated.[100] Damage to the brain generally does not occur until temperatures reach 42.0 C (107.6 F), and it is rare for an untreated fever to exceed 40.6 C (105.1 F).[101] Treating fever in people with sepsis does not affect outcomes.[102] Small trials have shown no benefit of treating fevers of 38.5 C (101.3 F) or higher of critically ill patients in ICUs, and one trial was terminated early because patients receiving aggressive fever treatment were dying more often.[19]
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