Potassium chloride supplementation alone may not improve hypokalemia in thyrotoxic hypokalemic periodic paralysis.

This article reports a 29-year-old man who came to the Emergency Department because of sudden onset of bilateral lower extremity weakness and inability to walk after intake of a high carbohydrate meal and alcohol. He was found to have severe hypokalemia, with K(+) level at 1.7 mmol/L. However, after administration of potassium chloride (KCl), 10 mEq/h intravenous (i.v.) drip for 4 h, follow-up serum potassium was even lower at 1.5 mmol/L and the patient complained of persistent weakness. Twenty mg of propranolol, a non-selective beta-blocker, was given orally and a dramatic improvement of muscle power to grade 5 was noted after 30 min of administration. On the fifth day after discharge, he had another episode of bilateral lower extremity weakness after ingesting a mouthful of alcohol. Muscle power recovered completely after i.v. drip of KCl, 20 mEq. Laboratory data revealed an underlying primary hyperthyroidism for which he was given anti-thyroid agents and beta-blockers.