Non-environmental accidental hypothermia

Specialty: Geriatrics.

• endogenous hypothermia in the elderly
• hypothermic thermal deregulation
• senile thermogenic failure
• internal hypothermia

Why it occurs

• Severe autonomic neuropathy that prevents correct protective peripheral vasoconstriction against cooling
• Massive decrease in skeletal muscle mass (extreme sarcopenia) that nullifies thermogenic capacity through tremor or shivering
• Severe systemic sepsis (commonly due to gram-negative bacilli or pneumococcus) with atypical presentation and absence of pyrogenic response
• Extreme protein-calorie malnutrition with total depletion of brown fat and liver glycogen reserves
• Hypopituitarism or chronic decompensated adrenal insufficiency in the elderly patient

Initial workup

Continuous core temperature measurement using low range rectal probe; obtaining serial blood and urine cultures; urgent blood analysis that includes glucose, urea, creatinine, serum electrolytes (sodium, potassium, calcium), arterial blood gases, lactate, serum cortisol at 8:00 a.m., TSH and free T4; continuous electrocardiographic monitoring; portable chest x-ray.

Standard management

• Hot crystalloid solutions — 0.9% saline solution heated to 38-40 °C intravenously, infused at a controlled rate of 50-80 ml/h to avoid acute lung edema in the context of concomitant diastolic dysfunction
• Hydrocortisone — 100 mg intravenously every 8 hours when a precipitating adrenal crisis is suspected, always administered before starting any thyroid hormone replacement
• Levothyroxine (100 mcg to 200 mcg intravenous as a single bolus if myxedema coma is suspected, closely monitoring to avoid myocardial ischemia).