What is hyperpyrexia?
In medical term, pyrexia means fever and hyperpyrexia means extremely high rise of body temperature or fever, where body temperature rises equal to or higher than 41.5 °C or 106.7 °F. Extreme rise in body temperature of hyperpyrexia is medical emergency, as it may be an indication of serious underlying medical disorder and lead to serious consequences and measures must be taken to bring down body temperature immediately to within normal limit. Hyperpyrexia most commonly occurs due to intracranial hemorrhage (bleeding inside brain).
Hyperpyrexia may also occur due to (although less frequently) sepsis, viral infection (rubeola, enterovirus infection, roseola etc.), Kawasaki syndrome, malignant syndrome, as a side effect of certain medications, thyroid storm etc. The most common cause of fever is infection (by bacteria or virus), although hyperpyrexia causes may be non-infectious. Patients suffering from hyperpyrexia should be aggressively treated (cooled using cold sponging and nursing the patient in a cool room, preferably air conditioned room) to bring down body temperature below 38.9 °C or 102.0 °F, which can improve outcome of the problem.
What is hyperthermia?
In hyperthermia, there is uncontrolled rise in body temperature due to excessive production of body heat and body can not loose enough heat to control body temperature, although the hypothalamic temperature regulation “set point” is not raised. Hyperthermia can occur when there is exposure to exogenous heat coupled with excessive production of endogenous heat, as seen in sunstroke/heatstroke and in case of strenuous work/exercise in hot and humid environment, although physiologic thermoregulation is intact but fail to loose enough heat than produced.
Examples of hyperthermia includes heatstroke or sunstroke, malignant hyperthermia, drug induced hyperthermia [amphetamines, cocaine, phencyclidine (PCP), methylenedioxymethamphetamine (MDMA also known commonly as “ecstasy”), lysergic acid diethylamide (LSD), salicylates, lithium, anticholinergics, sympathomimetics], due to damage of central nervous system etc.
What is the difference between hyperpyrexia and hyperthermia?
Hyperpyrexia differs from hyperthermia in that, in case of hyperpyrexia the body temperature regulation “set point” is first set above the normal set point (just like in case of fever) and then the body generate heat to reach at the set point. Whereas in case of hyperthermia, body temperature rises above the temperature regulation “set point”, which cause extreme rise in body temperature.