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Myxedema coma

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myxedema coma treatment guideline intravenous levothyroxine hydrocortisone American Thyroid Association

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https://www.ncbi.nlm.nih.gov/books/NBK279007

Myxedema coma

Myxedema coma is a rare, life-threatening decompensation of severe, longstanding hypothyroidism. Despite its name, patients are often not actually comatose. It is an ICU emergency.

Typical presentation

Think of the triad:
  • Altered mental status: lethargy, confusion, stupor, or coma
  • Hypothermia
  • Hypoventilation/respiratory depression
Other findings include bradycardia, hypotension, hyponatremia, hypoglycemia, reduced reflexes, puffy/coarse skin, and sometimes pericardial effusion. It often follows a precipitating stressor in a patient with untreated or undertreated hypothyroidism.
ROSEN's Emergency Medicine, lines 348-351; Goodman & Gilman's Pharmacological Basis of Therapeutics, lines 2467-2471.

Common precipitants

  • Infection, including pneumonia or UTI
  • Stopping or missing levothyroxine
  • Cold exposure
  • Surgery, trauma, stroke, myocardial infarction, or heart failure
  • Sedatives, opioids, anesthetics, or other CNS depressants
  • GI bleeding or metabolic disturbance

Investigations

Do not delay treatment while waiting for results.
  • TSH and free T4, often high TSH with very low free T4 in primary hypothyroidism
  • Serum cortisol before steroids if this does not delay therapy
  • Glucose, electrolytes, ABG/VBG, CBC, renal and liver tests
  • ECG, chest imaging, cultures, and evaluation for infection/MI/stroke or another trigger
  • Consider central hypothyroidism if TSH is low or inappropriately normal despite low free T4.

Immediate management

  1. ICU care, ABCs
    • Supplemental oxygen and early intubation/mechanical ventilation if hypoventilation, hypercapnia, or impaired airway protection.
    • Cautious IV fluids and vasopressors if needed.
  2. Give stress-dose glucocorticoids first
    • Example: hydrocortisone 100 mg IV every 8 hours.
    • Draw cortisol beforehand if feasible, but do not delay therapy. Steroids protect against unrecognized adrenal insufficiency, which thyroid-hormone treatment can unmask. ATA guideline recommendations
  3. IV levothyroxine (T4)
    • Loading: 200-400 micrograms IV once
    • Then about 1.6 micrograms/kg/day, using roughly 75% of the equivalent oral dose while IV. Use a lower load/maintenance dose in older patients or those with coronary disease or arrhythmia. ATA/Endotext guidance
  4. Consider IV liothyronine (T3) selectively
    • May be added in severe cases or inadequate clinical response.
    • A commonly cited regimen is 5-20 micrograms IV loading, then 2.5-10 micrograms IV every 8 hours.
    • Avoid excessive doses because tachyarrhythmia and myocardial ischemia are concerns, especially in elderly or cardiac patients. ATA guideline recommendations
  5. Supportive treatment
    • Passive warming with blankets. Avoid aggressive peripheral active rewarming because vasodilation can worsen hypotension.
    • Correct hypoglycemia with dextrose.
    • Correct severe hyponatremia carefully.
    • Identify and treat the trigger. Give empiric antibiotics when infection is suspected.

Monitoring

Monitor mental status, temperature, respiratory function/ABGs, ECG and cardiac status, blood pressure, glucose, fluid balance, sodium, and free T4/T3 every 1-2 days initially. TSH improves slowly and is not useful for immediate response assessment.

Key exam point

Sequence: ICU stabilization -> cortisol sample if feasible -> IV hydrocortisone -> IV levothyroxine -> treat precipitating cause and complications.
Published recommendations are based largely on expert consensus and case data because this condition is too rare for practical randomized trials. No recent systematic review/meta-analysis was found in the last 2 years.
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