Treatment of Myxedema Coma
The definitive treatment for myxedema coma requires immediate hospitalization in an intensive care unit with intravenous thyroid hormone replacement, specifically liothyronine (T3) at an initial dose of 5-20 μg followed by 2.5-10 μg every 8 hours, along with hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out. 1, 2
Initial Assessment and Stabilization
- Immediate hospitalization in an intensive care unit is essential for aggressive supportive care, with focus on maintaining airway, breathing, and circulation; intubation and ventilation may be necessary if Glasgow Coma Score ≤8 1
- Correct hypoglycemia immediately if present, as it can worsen neurological status 1
- Administer hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is ruled out, as hypothyroidism and adrenal insufficiency often coexist 1
- Manage hypothermia with passive rewarming to avoid vasodilation and cardiovascular collapse 1
Thyroid Hormone Replacement
- For myxedema coma, intravenous liothyronine (T3) is preferred due to its rapid onset of action and the impaired peripheral conversion of T4 to T3 often seen in critically ill patients 2, 3
- Initial dosing of intravenous liothyronine should be 5-20 μg followed by 2.5-10 μg every 8 hours, with careful monitoring of cardiovascular response 2
- Alternatively, a combination therapy of 200 μg levothyroxine and 50 μg liothyronine can be used for the first few days, followed by levothyroxine monotherapy 3
- In elderly patients or those with cardiac disease, consider lower initial doses (25-50 μg) to avoid cardiovascular complications 1
- When intravenous formulations are unavailable, oral levothyroxine can be used as an alternative with loading doses of 300-500 μg, followed by tapering over 3-5 days 4
Supportive Care
- Correct hyponatremia gradually to avoid central pontine myelinolysis; hypertonic saline should be avoided unless serum sodium is <120 mEq/L with neurological symptoms 1
- Treat hypothermia with passive rewarming methods only; active rewarming can cause vasodilation and cardiovascular collapse 1
- Identify and treat precipitating factors such as infections, medications (sedatives, anesthetics), or concurrent illness 5
- Monitor for and treat bradycardia, hypotension, and respiratory depression 5
- Provide ventilatory support as needed for hypoventilation and CO2 retention 1
Transition to Maintenance Therapy
- Once the patient stabilizes, transition to oral levothyroxine at a maintenance dose of 1.6 μg/kg/day for patients without risk factors 1
- For elderly patients or those with cardiac disease, start with 25-50 μg daily and titrate gradually 1
- Monitor thyroid function tests every 6-8 weeks while titrating to goal TSH within reference range 1
- Be vigilant for patients who may decompensate during transition from IV to oral therapy; some patients may require prolonged IV therapy before successful transition 5
Pitfalls and Caveats
- Delayed diagnosis significantly increases mortality; maintain high clinical suspicion in elderly patients with altered mental status, hypothermia, and bradycardia 5
- Avoid excessive thyroid hormone replacement in elderly patients or those with cardiovascular disease as it may precipitate arrhythmias or myocardial infarction 1, 6
- Monitor for adrenal crisis, which can be precipitated by thyroid hormone replacement in patients with concurrent adrenal insufficiency 7
- Be aware that oral absorption of levothyroxine may be variable in critically ill patients, particularly those with gastrointestinal dysfunction 6
- Recognize that myxedema coma has a high mortality rate (30-60%) even with appropriate treatment, emphasizing the need for aggressive management 3