Non-febrile hypothermia in the elderly

Specialty: Geriatrics.

• senile accidental hypothermia
• hypothermic thermal deregulation
• spontaneous low body temperature in the elderly

Why it occurs

• Physiological decrease in thermogenesis due to shivering and alteration of cutaneous vasoconstriction due to autonomic aging
• Severe undiagnosed or decompensated hypothyroidism (early phase of myxedema coma)
• Severe bacterial sepsis or septic shock with an atypical course presenting with hypothermia instead of fever
• Chronic adrenal insufficiency or latent Addisonian crisis in patients with extreme fragility
• Central toxicity or adverse effects from psychotropic drugs (especially phenothiazines, long-acting benzodiazepines or acute alcohol consumption) that depress the hypothalamic thermostat

Initial workup

Measurement of core temperature using continuous rectal thermometry with low range devices; 12-lead electrocardiogram looking for the presence of Osborn J waves and prolongation of the PR, QRS and QT intervals; urgent blood analysis with complete blood count, blood glucose, serum electrolytes, creatinine, urea, thyroid profile (TSH, free T4), morning basal cortisol, arterial blood gas and serum lactate levels; obtaining blood and urine cultures if occult sepsis is suspected.

Standard management

• Infusion of heated intravenous crystalloid solutions — 0.9% physiological saline warmed to 37-40 °C for volume replacement if hypotension exists, closely monitoring central venous pressure or ultrasound to avoid the development of acute pulmonary edema
• Hydrocortisone — 100 mg intravenously every 8 hours when concomitant adrenal insufficiency is suspected to avoid precipitation of an acute adrenal crisis during the rewarming process
• Levothyroxine sodium (100 mcg to 200 mcg directly intravenously only if a diagnosis of myxedema coma is confirmed, always administered after hydrocortisone).