Chapter 131: Thyroid Disease Emergencies

HYPOTHYROIDISM AND MYXEDEMA COMA

Hypothyroidism may be caused by multiple factors. Myxedema coma (also called myxedema crisis) 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 Fig. 131-1. Patients with myxedema coma have hypothyroidism and present with metabolic and multi-organ decompensation, including hypothermia, bradycardia, hypotension, and altered mental status. Respiratory insufficiency and altered mental status can result from CO₂ narcosis, and a difficult airway may be encountered due to macroglossia, glottic, and oropharyngeal edema. Laboratory abnormalities include hypoglycemia and hyponatremia.

Diagnosis and Differential

The diagnosis of myxedema coma is clinical. 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 includes sepsis, depression, adrenal crisis, congestive heart failure, hypoglycemia, stroke, hypothermia, meningitis, and drug overdose.

Emergency Department Care and Disposition

Management of myxedema coma includes:

1. Supportive care with airway stabilization, mechanical ventilation, and cardiac monitoring. 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 hydrocortisone100 mg IV for suspected adrenal insufficiency. Correct hypoglycemia.

3. Thyroid replacement therapy: Levothyroxine (T4) 4 µg/kg, followed in 24 hours by 100 µg IV, then 50 µg IV until oral medication is tolerated or liothyronine (T3) 20 μg IV followed by 10 µg IV every 8 hours until the patient is conscious for severe myxedema coma. Start with no more than 10 µg IV in the elderly and patients with cardiovascular disease. Switch to levothyroxine 50 to 200 µg/day PO when the patient is ambulatory.

4. Admit patients to a monitored or ICU setting.

5. Identify and treat precipitating factors

   • Infections

   • Sedatives

   • Anesthetic agents (e.g., etomidate)

   • Cold exposure

   • Trauma

   • Myocardial infarction or congestive heart failure

   • Cerebrovascular accident

   • GI hemorrhage

   • Contributing metabolic conditions include hypoxia, hypercapnia, hyponatremia, and hypoglycemia

THYROTOXICOSIS AND THYROID STORM

Hyperthyroidism refers to excess circulating hormone due to thyroid gland hyperfunction, whereas thyrotoxicosis refers to excess circulating thyroid hormone from any cause. Thyroid storm is an acute, life-threatening state of thyrotoxicosis that is most common in patients with antecedent Graves' disease.

Clinical Features

The clinical features of thyrotoxicosis are manifestations of enhanced adrenergic activity. Signs and symptoms are shown in Table 131-1. As for thyroid storm, the leading signs and symptoms are constitutional (fever), central nervous system related (agitation, ...