Chapter 131. Thyroid Disease Emergencies

Hypothyroidism may be caused by multiple factors. Myxedema coma is a rare, life-threatening expression of hypothyroidism. It may be precipitated by infection, cold exposure, trauma, medications, or myocardial infarction. It classically occurs during the winter months in elderly women with undiagnosed or undertreated hypothyroidism.

Clinical Features

The presentation of hypothyroidism is summarized in Figure 131-1. Patients with myxedema coma have hypothyroidism and present with hypothermia, bradycardia, hypotension, and altered mental status. Respiratory failure is common and a difficult airway may be encountered due to macroglossia and oropharyngeal edema. Laboratory abnormalities include hypoglycemia and hyponatremia.

Diagnosis and Differential

Myxedema coma is a clinical diagnosis. Send confirmatory thyroid studies, but do not delay treatment for test results. Low free thyroxine (FT4) and triiodothyronine (FT3), and elevated thyroid stimulating hormone (TSH) are diagnostic. The differential diagnosis for myxedema coma includes sepsis, adrenal crisis, congestive heart failure, hypoglycemia, stroke, hypothermia, and drug overdose.

Emergency Department Care and Disposition

1. Provide supportive care with airway stabilization, mechanical ventilation, and cardiac monitoring (Table 131-1). Treat hypotension with fluid resuscitation. Vasopressors may be ineffective until thyroid hormone replacement is initiated. Passively rewarm hypothermic patients.

2. Seek out and treat precipitating causes. Administer hydrocortisone 100 milligrams IV for suspected adrenal insufficiency. Correct hypoglycemia.

3. Administer levothyroxine (T4) 4 micrograms/kilogram IV by slow infusion. Add liothyronine (T3) 20 micrograms IV for severe myxedema coma. Use liothyronine with caution in the elderly and patients with cardiovascular disease.

4. Patients should be admitted to a monitored or ICU setting.