Fever And Hyperthermia
Fever is an elevation of body temperature that exceeds the normal daily variation and occurs in conjunction with an increase in the hypothalamic set point.
just like the thermostat of a room is set up its the same way the shift from normothermic to the new set point. Many processes take place during this:
a. Vasomotor center in the brain is activated.
b. Vasoconstriction commences. First in the hands and the feet which leads to stopped blood flow in periphery.
c. This decreases heat loss from the skin and thus person feels cold.
To compensate this some processes take place:
a. Shivering which increases the heat production from the muscles start to happen.
b. Shivering might not happen if heat conservation mechanisms are going on.
c. Non-shivering mechanism like heat production from the liver may help by keeping increased core temp of the body.
d. Behavioral adjustments like clothing etc may also help to conserve heat.
The heat conservation or the vasoconstriction occurs untill the blood bathing the hypothalamic neurons match the new thermostat.
Now after the level of pryogen comes down in the body or the use of antipyretics the hypothalamic set point is again set to a lower point. This also initiate some processes:
a. Vasodilation occurs.
b.sweat glands are activated so there is a loss of heat by sweating
these processes continue till the blood temp matches to the lower set point o the hypothalamus.
Hyperpyrexia: when there is a fever of temp more than 41 degree C. This kind of fever develop in people with severe infections. most commonly it happens to people with damage in the CNS(CNS hemorrhage)
There are some rare cases when the hypothalamic set point is raised like trauma, hemorrhage, tumor or intrinsic hypothalamic damage(hypothalamic fever).
Although most patients with elevated body temp have fever there are situations when elevated body temp means hyperthermia.
Hyperthermia is characterized by an uncontrolled increase in the body temperature that exceeds the body's ability to loose heat. More body heat then the body is able to loose to maintain a normal body temperature.
It does not involve the pryogen molecules but may be caused due to exogenous heat exposure or endogenous heat production or both. Hyperthermia can be occur after there is a heat stroke.
The two mechanisms of hyperthemia both exogenous and endogenous can be fatal as they can cause dangerously high internal body temperatures.
It becomes important to distinguish between fever and hyperthermia because high temp in hyperthermia is fatal and does not respond to antipyretics(fever reducing medicines).
It becomes difficult to distinguish between the two during an emergency but can be done by the preceding events
If temp more than 40 degree C then there is a chance of hyperpyrexia. Whereas the hyperthemia is often diagnosed with the events immediately preceding the elevation of core temperature like eg. heat exposure or treatment with drugs to interfere with thermoregulation. in patients with heat stroke or people who take sweat blocking drugs the skin is hot but dry. Antipyretics do not help in this situation and it might be given in hyperpyrexia.
in case of hyperthemia we should try to bring down the body temp by placing the person in cool place ,behavioral change like clothing etc.
just like the thermostat of a room is set up its the same way the shift from normothermic to the new set point. Many processes take place during this:
a. Vasomotor center in the brain is activated.
b. Vasoconstriction commences. First in the hands and the feet which leads to stopped blood flow in periphery.
c. This decreases heat loss from the skin and thus person feels cold.
To compensate this some processes take place:
a. Shivering which increases the heat production from the muscles start to happen.
b. Shivering might not happen if heat conservation mechanisms are going on.
c. Non-shivering mechanism like heat production from the liver may help by keeping increased core temp of the body.
d. Behavioral adjustments like clothing etc may also help to conserve heat.
The heat conservation or the vasoconstriction occurs untill the blood bathing the hypothalamic neurons match the new thermostat.
Now after the level of pryogen comes down in the body or the use of antipyretics the hypothalamic set point is again set to a lower point. This also initiate some processes:
a. Vasodilation occurs.
b.sweat glands are activated so there is a loss of heat by sweating
these processes continue till the blood temp matches to the lower set point o the hypothalamus.
Hyperpyrexia: when there is a fever of temp more than 41 degree C. This kind of fever develop in people with severe infections. most commonly it happens to people with damage in the CNS(CNS hemorrhage)
There are some rare cases when the hypothalamic set point is raised like trauma, hemorrhage, tumor or intrinsic hypothalamic damage(hypothalamic fever).
Although most patients with elevated body temp have fever there are situations when elevated body temp means hyperthermia.
Hyperthermia is characterized by an uncontrolled increase in the body temperature that exceeds the body's ability to loose heat. More body heat then the body is able to loose to maintain a normal body temperature.
It does not involve the pryogen molecules but may be caused due to exogenous heat exposure or endogenous heat production or both. Hyperthermia can be occur after there is a heat stroke.
The two mechanisms of hyperthemia both exogenous and endogenous can be fatal as they can cause dangerously high internal body temperatures.
It becomes important to distinguish between fever and hyperthermia because high temp in hyperthermia is fatal and does not respond to antipyretics(fever reducing medicines).
It becomes difficult to distinguish between the two during an emergency but can be done by the preceding events
If temp more than 40 degree C then there is a chance of hyperpyrexia. Whereas the hyperthemia is often diagnosed with the events immediately preceding the elevation of core temperature like eg. heat exposure or treatment with drugs to interfere with thermoregulation. in patients with heat stroke or people who take sweat blocking drugs the skin is hot but dry. Antipyretics do not help in this situation and it might be given in hyperpyrexia.
in case of hyperthemia we should try to bring down the body temp by placing the person in cool place ,behavioral change like clothing etc.
Interesting..!!
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