Management of myxedema coma: report on three successfully treated cases with nasogastric or intravenous administration of triiodothyronine.

Three consecutive cases of myxedema coma treated successfully with either nasogastric or intravenous route of administration of I-triiodothyronine, followed by oral thyroxine, are described. All were hypothermic, had biochemical evidence of advanced hypothyroidism (T4 less than 1.0 micrograms/dl, T3 less than 20 ng/dl and TSH greater than 150 microU/ml), severe hypoxemia, respiratory acidosis, hypercarbia and temporary depression of respiratory center responsiveness. In only one patient it was found significant hyponatremia (Na = 127 mEq/l). Two patients were successfully treated with the nasogastric route of administration of T3 (12.5 micrograms/6h) but in a female patient with intestinal atony (ileus) there was no absorption of the orally administered T3. Intravenously administered T3 promptly corrected the hypometabolic state in this patient. It was confirmed that T4 therapy, although promptly correcting low serum T4 concentration, failed to rise serum T3 levels due to lack of peripheral T4 5'-monodeiodination to T3 in these critically ill patients.