Myxoedema coma
Myxoedema coma is a medical emergency caused by severe untreated hypothyroidism. It typically presents with impaired consciousness, hypoventilation and hypothermia. Arrange immediate transport to hospital by ambulance, with airway support, for care in a high-dependency ward. In addition to thyroid hormone replacement, manage fluid and electrolyte balance, temperature, and glucocorticoid deficiency (see Adrenal crisis for glucocorticoid doses).
Myxoedema coma is a rare condition with limited evidence to guide management. Intravenous therapy is favoured over oral levothyroxine therapy because it has a more rapid onset, and because absorption of oral therapy may be limited by intestinal pseudo-obstruction.
A typical regimen is:
levothyroxine 300 micrograms by slow intravenous injection over 30 minutes as a loading dose, then 1.2 micrograms/kg (to the nearest 25 micrograms) intravenously, daily1. myxoedema coma, initial intravenous therapy levothyroxine
If intravenous therapy is not available and oral administration is possible, use:
levothyroxine 500 micrograms orally, as a loading dose, then 1.6 micrograms/kg (to the nearest 25 micrograms) orally, daily. myxoedema coma, initial oral therapy levothyroxine
Conversion of thyroxine (T4) to triiodothyronine (T3) can be impaired in patients with myxoedema coma. If the patient’s condition has not improved after 24 hours of levothyroxine therapy, consider adding liothyronine. Use:
liothyronine 20 micrograms by slow intravenous injection over 30 minutes, twice daily2. myxoedema coma liothyronine
Once the patient is conscious, and if there is no evidence of intestinal pseudo-obstruction, start oral therapy and continue intravenous therapy for the first 3 to 5 days of oral therapy. Use:
levothyroxine 1.6 micrograms/kg (to the nearest 25 micrograms) orally, daily. myxoedema coma, subsequent oral therapy levothyroxine
Measure serum T4, T3 and thyroid stimulating hormone (TSH) concentrations after 3 to 5 days. Subsequent management for the untreated hypothyroidism is usually required. See Thyroxine replacement therapy in adults or Hypothyroidism in children for more information.