What is the management of myxedema?

Management of Myxedema

The management of myxedema coma requires immediate intensive care with intravenous levothyroxine (200-400 mcg initially) followed by daily maintenance doses, along with supportive measures including ventilatory support, fluid resuscitation, and stress-dose corticosteroids.

Identification and Assessment

Myxedema coma is a life-threatening medical emergency characterized by:

• Severe decompensation of hypothyroidism
• Altered mental status ranging from lethargy to coma
• Hypothermia (often <95°F/35°C)
• Hypotension
• Hypoventilation with hypercapnia
• Hyponatremia
• Bradycardia

Common precipitating factors include:

• Infections (most common)
• Discontinuation of thyroid medication
• Sedatives or anesthetics
• Trauma
• Stroke
• Myocardial infarction
• Cold exposure

Treatment Protocol

Immediate Management

1. Thyroid Hormone Replacement:

   • Intravenous levothyroxine (T4): Initial loading dose of 200-400 mcg IV, followed by 50-100 mcg daily 1
   • Alternative approach: Combination therapy with levothyroxine 200 μg and liothyronine 50 μg until clinical improvement 2
   • For patients with known or suspected cardiac disease, use lower initial doses (100-200 mcg) 1

2. Corticosteroid Administration:

   • Administer hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out 1
   • Critical: Ensure adequate cortisol replacement BEFORE thyroid hormone normalization to prevent precipitating adrenal crisis 1

3. Supportive Care:

   • Airway management and ventilatory support as needed
   • Fluid resuscitation with 0.9% saline to address hypotension
   • Passive rewarming for hypothermia (avoid active rewarming which can cause vasodilation and cardiovascular collapse)
   • Correction of electrolyte abnormalities, particularly hyponatremia
   • Treatment of precipitating factors, especially infections

Monitoring and Ongoing Management

• Continuous cardiac monitoring for arrhythmias
• Frequent vital sign assessment
• Daily thyroid function tests (TSH, free T4)
• Blood glucose monitoring (risk of hypoglycemia)
• Electrolyte monitoring and correction

Management of Mild to Moderate Myxedema

For non-comatose myxedema:

• Oral levothyroxine: Starting dose based on severity and patient characteristics 3:

  • Mild hypothyroidism: 25 mcg daily, increasing by 25 mcg every 1-2 weeks
  • Myxedema (severe hypothyroidism): Start with 5 mcg daily, increase by 5-10 mcg every 1-2 weeks
  • Maintenance dose typically 50-100 mcg daily

• For elderly patients or those with cardiac disease: Start at lower doses (12.5-25 mcg daily) and titrate more slowly 4

Special Considerations

• Cardiac monitoring: Thyroid hormone replacement can exacerbate underlying coronary artery disease or precipitate arrhythmias
• Age consideration: Higher mortality is associated with advanced age, cardiac complications, and excessive thyroid hormone replacement 5
• Medication interactions: Adjust dosing if patient is on medications that affect thyroid hormone metabolism (e.g., phenytoin, carbamazepine)

Prognosis and Follow-up

• Mortality rates for myxedema coma remain high (20-40%) despite treatment

• Poor prognostic factors include:

  • Advanced age
  • Persistent hypothermia
  • Bradycardia at presentation
  • Need for mechanical ventilation
  • Sepsis
  • High APACHE II and SOFA scores >6 6

• After stabilization, transition to oral levothyroxine with regular monitoring of thyroid function tests

Prevention

• Ensure patient education about the importance of medication adherence
• Provide extra thyroid hormone doses during periods of acute illness
• Regular follow-up to monitor thyroid function and adjust medication as needed

The key to successful management of myxedema is early recognition, prompt thyroid hormone replacement, and aggressive supportive care in an intensive care setting.