Myxedema Coma

Myxoedema coma is severe decompensated hypothyroidism with altered mental status and hypothermia.

• Mostly elderly women in winter with long standing untreated hypothyroidism.
• Precipitants: infection, cold exposure, sedatives, opioids, stroke, heart failure, gastrointestinal bleeding, stopping levothyroxine, amiodarone.
• Mortality 30 to 50%.

• Depressed consciousness (rarely true coma), hypothermia (below 35 C), bradycardia, hypotension.
• Hypoventilation with hypercapnia, hyponatraemia, hypoglycaemia.
• Periorbital oedema, macroglossia, dry skin, delayed relaxation of reflexes, pericardial effusion, ileus.
• Scalar score: Popoveniuc diagnostic score guides likelihood.

• High TSH with low free T4 (TSH may be inappropriately normal in central or sick patients).
• Blood gas (hypercapnia), glucose, sodium, creatine kinase, cortisol (before steroids), lactate, cultures, ECG, chest radiograph, echocardiogram.
• Look for precipitating illness.

• ICU care, ventilation for hypercapnia, passive rewarming.
• Hydrocortisone 100 mg IV every 8 hours until adrenal insufficiency is excluded.
• Levothyroxine IV 200 to 400 micrograms loading, then 1.6 micrograms/kg/day (75% of dose IV, lower, 50 to 100 micrograms daily, in elderly or cardiac disease); consider adding liothyronine 5 to 20 micrograms IV loading then 2.5 to 10 micrograms every 8 hours.
• Treat infection with broad spectrum antibiotics after cultures.
• Correct hyponatraemia (fluid restriction, hypertonic saline if severe), hypoglycaemia (dextrose).
• Avoid sedatives; careful fluids; vasopressors for refractory hypotension.
• Transition to oral levothyroxine when conscious.