Treatment of Myxedema Coma
Myxedema coma requires immediate intravenous liothyronine (T3) administration as the first-line treatment, with an initial dose of 5-20 mcg IV followed by 5-10 mcg every 8-12 hours until clinical improvement occurs. 1
Diagnosis and Initial Assessment
Myxedema coma is a life-threatening emergency characterized by:
- Altered mental status/coma
- Hypothermia
- Bradycardia
- Hypotension
- Hypoventilation
- Hyponatremia
- Hypoglycemia
Precipitating Factors
- Infection (most common)
- Cold exposure
- Medications (sedatives, anesthetics)
- Surgery
- Stroke
- Myocardial infarction
Treatment Algorithm
Immediate Interventions (First Hour)
Airway management
- Secure airway - anticipate potential difficult intubation due to posterior pharyngeal edema 2
- Mechanical ventilation if needed
Thyroid hormone replacement
- First choice: Liothyronine (T3) IV - 5-20 mcg IV bolus, then 5-10 mcg every 8-12 hours 1
- Alternative if IV T3 unavailable: Levothyroxine (T4) IV - 300-500 mcg IV loading dose, then 50-100 mcg daily
Stress-dose glucocorticoids
- Hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out
Supportive care
- Passive rewarming (avoid active rewarming which may cause vasodilation and cardiovascular collapse)
- Fluid resuscitation with careful monitoring (risk of heart failure)
- Glucose administration for hypoglycemia
- Treatment of precipitating factors (especially antibiotics if infection suspected)
Monitoring
- Continuous cardiac monitoring
- Frequent vital signs
- Serial thyroid function tests (TSH, free T4, T3)
- Electrolytes, particularly sodium (risk of hyponatremia)
- Blood glucose levels
- Mental status assessment
Special Considerations
When IV Thyroid Hormone is Unavailable
If IV thyroid hormone preparations are not available, oral levothyroxine can be used as an alternative:
- Loading dose: 300-500 μg orally
- Followed by 100-150 μg daily 3
- Recent evidence suggests oral levothyroxine can be effective even in myxedema coma when IV formulations are unavailable 4, 3
Common Pitfalls
- Delayed diagnosis - High clinical suspicion is crucial as laboratory confirmation may take time
- Inadequate initial dosing - Underdosing thyroid hormone replacement can lead to treatment failure
- Failure to identify and treat precipitating factors
- Overlooking adrenal insufficiency - Always cover with stress-dose steroids initially
- Aggressive rewarming - Can precipitate cardiovascular collapse
- Underestimating airway difficulties - Prepare for difficult intubation due to potential pharyngeal edema 2
Prognosis
- Mortality remains high (20-40%) despite appropriate treatment
- Poor prognostic factors include:
- Advanced age
- Prolonged duration of coma
- Severity of hypothermia
- Presence of multiple comorbidities
- Delayed treatment initiation
Early recognition and aggressive treatment are essential to improve outcomes in this rare but potentially fatal endocrine emergency.