Emergency Treatment of Myxedema Coma
Myxedema coma requires immediate ICU admission with aggressive supportive care and concurrent administration of intravenous thyroid hormone replacement plus empiric glucocorticoids—treatment must begin on clinical suspicion without waiting for laboratory confirmation. 1, 2, 3
Immediate Stabilization (First Hour)
Airway and Breathing:
- Intubate and mechanically ventilate if Glasgow Coma Score ≤8 or if respiratory failure is present 1
- Administer 100% oxygen to all patients 3
Circulation:
- Establish large-bore IV access immediately 3
- Correct hypotension with IV fluids, but use caution as these patients have impaired free water clearance 3
- Correct hypoglycemia immediately if present 1
Empiric Glucocorticoid Coverage:
- Administer hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out 1, 2, 3
- This is critical because thyroid hormone replacement can precipitate adrenal crisis in patients with concurrent adrenal insufficiency 1
Thyroid Hormone Replacement
Intravenous Levothyroxine (Preferred):
- The FDA-approved intravenous liothyronine (Triostat®) is specifically marketed for myxedema coma 4
- Most authorities recommend intravenous levothyroxine (T4) as opposed to intravenous liothyronine (T3) 3
- Loading dose strategy is recommended, though specific dosing should account for cardiovascular risk 1, 4
When IV Formulation is Unavailable:
- Oral levothyroxine can be effective: loading dose of 300-500 μg, followed by taper over the next 3-5 days 5
- A case series of 14 patients treated with oral levothyroxine showed 13/14 survival when IV formulation was unavailable 5
- Crushed tablets can be administered through enteral route 6, 5
Critical Dosing Consideration:
- Elderly patients or those with known cardiovascular disease require lower initial doses (25-50 μg) to avoid cardiovascular complications 1
- However, in myxedema coma, the life-threatening nature may necessitate higher loading doses despite cardiac risk 4, 5
Supportive Care Priorities
Temperature Management:
- Rewarm slowly using passive external warming only 3
- Avoid active rewarming which can cause vasodilation and cardiovascular collapse 3
Electrolyte Correction:
- Correct hyponatremia cautiously with hypertonic saline if severe 3
- Hypothyroidism should be included in the differential diagnosis of every patient with hyponatremia 3
Identify and Treat Precipitating Factors:
- Infection is the most common precipitant—obtain cultures and start broad-spectrum antibiotics empirically 2, 5
- Other precipitants include myocardial infarction, cold exposure, surgery, and sedating medications 2, 3
Monitoring During Acute Phase
Cardiovascular Monitoring:
- Continuous cardiac monitoring for bradycardia and arrhythmias 7
- Watch for Osborne J-waves on ECG, which indicate severe hypothermia and poor prognosis 7
- Monitor for sudden cardiovascular decompensation even after treatment initiation 7
Laboratory Monitoring:
- Recheck TSH and free T4 every 6-8 weeks while titrating to goal of TSH within reference range 1
- Monitor for improvement in mental status, temperature, and hemodynamics 2
Critical Pitfalls to Avoid
Never delay treatment for laboratory confirmation:
- The mortality rate is extremely high, and treatment must begin immediately upon clinical suspicion 1, 2, 3
Never give thyroid hormone without glucocorticoid coverage:
Never use full replacement doses in elderly or cardiac patients initially:
- Start with 25-50 μg in these populations to prevent cardiac complications 1
Never actively rewarm the patient:
- This causes peripheral vasodilation and cardiovascular collapse 3
Transition to Maintenance
Once stabilized, transition to maintenance levothyroxine dosing: