Impaired thermoregulation
Decreased heat production
This category includes accidental hypothermia due to both immersion etiologies and nonimmersion etiologies and is the most common form of hypothermia encountered in the emergency department. Patients may present with induced vasodilatation from pharmacologic or toxicologic agents.
Hypothermia may be related to drug administration; such medications include beta-blockers, clonidine, meperidine, neuroleptics, and general anesthetic agents. Ethanol, phenothiazines, and sedativehypnotics also reduce the body’s ability to respond to low ambient temperatures.
Several etiologies related to endocrine derangements may cause decreased heat production. These include hypopituitarism, hypoadrenalism, and hypothyroidism. Consider all these conditions in patients presenting with unexplained hypothermia who fail to rewarm with standard therapy.
Other causes
A variety of causes may be associated with impaired thermoregulation, but, generally, it is associated with failure of the hypothalamus to regulate core body temperature. This may occur with CNS trauma, strokes, toxicologic and metabolic derangements, intracranial bleeding, Parkinson disease, CNS tumors, Wernicke disease, and multiple sclerosis.
Increased heat loss
