الفهرس | Only 14 pages are availabe for public view |
Abstract Thermoregulation is the ability of an organism to keep its body temperature within certain limits, even when the surrounding temperature is very different. If the body is unable to maintain a normal temperature and its temperature significantly increases above normal, a condition known as hyperthermia ensues. Although an elevated body temperature usually represents a fever in the vast majority of patients, there are a few occasions in which an elevated temperature is secondary to hyperthermia: heat stroke syndromes, certain metabolic diseases (hyperthyroidism), and use of drugs that interfere with thermoregulation. Both hyperthermia and fever result in an elevation of body temperature, but they differ physiologically. With fever, thermoregulatory mechanisms remain intact, but the hypothalamic thermal set point is raised by exposure to endogenous pyrogens, leading to behavioral and physiologic responses to elevate body temperature. In contrast to fever, during hyperthermia, the setting of the thermoregulatory center remains unchanged at normothermic levels, whereas body temperature increases in an uncontrolled fashion and overrides the ability to lose heat. 111 The conditions of hyperthermia due to drugs include: adrenergic fever caused, for example, by cocaine, amphetamines, designer drugs or monoamine oxidase (MAO) inhibitors; antidopaminergic fever, anti cholinergic fever, serotonergic fever and others. Other rare causes of hyperthermia include thyrotoxicosis and an adrenal gland tumor, called pheochromocytoma, both of which can cause increased heat production. Damage to the central nervous system, from brain hemorrhage, status epilepticus, and other kinds of injury to the hypothalamus can also cause hyperthermia. Exogenous heat exposure can also result in heat exhaustion oe heat stroke. Uncontrolled hyperthermia is independently associated with increased morbidity and mortality. Hyperthermia may cause rhabdomyolysis, liver failure, disseminated intravascular coagulation and multi-organ failure. It accentuates excitotoxic neurotransmitter release, increases production of oxygen free radical species, accelerates cytoskeleton protein degradation, and increases the risk of seizures. The presence of signs and symptoms related to hyperthermia syndromes, such as extrapyramidal symptoms characterstic of neuroleptic malignant 112 syndrome, and the presence of signs and symotoms more commonly related to infection-related fevers, are also considered in making the diagnosis .if fever-reducing drugs lower the body temperature, even if the temoerature does not return entirely to normal, then hyperthermia is excluded. To treat Hyperthermia, the underlying cause must be removed. Hyperthermia at or above 40°C is a life-threatening medical emergency that requires immediate treatment with adequate and efficient cooling measures. Hyperthermia that results from drug exposure requires prompt cessation of that drug, and occasionally the use of other drugs as counter measures |