A diagnosis that’s yours to make: Accidental hypothermia in the elderly

“Disruption of body temperature regulation has been attributed to antipsychotic agents. Both hyperthermia and hypothermia have been reported in association with Risperdal use. Caution is advised when prescribing for patients who will be exposed to temperature extremes.”¹²

Lorazepam very rarely may be associated with hypothermia. In animal studies, zolpidem, diazepam, and lorazepam produced comparable dose-dependent hypothermia.¹³ Ms. B. had her dosage of lorazepam increased from 0.5 mg 3 times daily to 0.5 mg 4 times daily because of increasing agitation and wandering. About 10 days before developing moderate hypothermia, she became more lethargic and the nursing staff was directed to withhold lorazepam if she appeared unduly sedated. At this point, Ms. B. may have had a drug-induced delirium superimposed upon dementia or a toxic-metabolic encephalopathy superimposed upon dementia. In her case, we do not know if druginduced or metabolic-induced changes (or a combination of the two) best explained her change in mental status.

Once accidental hypothermia sets in

During the days before Ms. B. developed moderate hypothermia, the temperature outside the assisted living facility ranged from 25°F to 40°F. When she was found by the nursing staff to be unusually unresponsive, she was wearing her nightgown under bed sheets. Even if her room temperature had been at 70°F, an almost 30°F gradient would exist between that and normal body temperature (98.6°F). In complete thermodysregulation, her body temperature of 84°F could have been reached within 5 to 8 hours. The colder the room, the faster her body would cool in the presence of thermodysregulation.

Although sepsis and adverse environmental exposure are the most common conditions leading to hypothermia, up to onethird of cases of accidental hypothermia in the elderly occur during the warmer months, with one-half of these cases found in the hospital.⁶ In cases of accidental hypothermia occurring during the winter, one-half occur in a normal room temperature setting.⁹

In a United Kingdom study, about 25% of elderly patients with hypothermia died.⁹ Still, the severity of underlying disease is more predictive of mortality than is the degree of hypothermia.¹⁴ Ms. B.’s fatal clinical course was that of multiple organ failure complicated by hypothermia. No mention was made in the hospital records of her vulnerability to hypothermia. This vulnerability placed significant burden on the assisted living facility staff.

Hypothermia should be considered in the differential diagnosis of confusion and disruptive behavior in the elderly patient. In Ms. B.’s case, an early diagnosis of accidental hypothermia by a psychiatrist could have made a difference.

Related resources Oriented to mental health issues

• Kramer MR, Vandijk J, Rosin AJ. Mortality in elderly patients with thermoregulatory failure. Arch Intern Med. 1989;149:1521-1523.
• Murphy PJ. Hypothermia. In Oxford Textbook of Geriatric Medicine. Evans JG, Williams TF, Beattie BL, Michel J-P, Wilcock GK, eds. New York: Oxford University Press, 2000:857-863.
• Jolly BT, Ghezzi KT. Accidental hypothermia. Emerg Med Clin North Am. 1992; 10:311-327.
• Fischbeck KH, Simon RP. Neurological manifestations of accidental hypothermia. Ann Neurol. 1981; 10:384-387.

Drug brand names

• Amlodipine • Norvasc
• Famotidine • Pepcid
• Isosorbide dinitrate • Isordil
• Lisinopril • Prinivil
• Metoclopramide • Reglan
• Metoprolol • Lopressor
• Oxybutynin • Ditropan
• Paroxetine • Paxil
• Risperidone • Risperdal
• Zolpidem • Ambien

Disclosure

The author reports that he is on the speakers’ bureau of Janssen Pharmaceutica, Eli Lilly and Co., Pfizer Inc., Wyeth-Ayerst Pharmaceuticals, Forest Pharmaceuticals, and GlaxoSmithKline.