Acute hypercapnic respiratory failure due to thyrotoxic periodic paralysis.

Acute hypercapnic respiratory failure is a potentially life-threatening complication of profound hypokalemia usually seen in patients with large total-body potassium (K+) deficits. It has rarely been reported in thyrotoxic periodic paralysis (TPP), which is due to intra-cellular shifts of K+. The authors report on a 29-year-old man who presented with sudden onset of muscle paralysis in all extremities and acute progressive respiratory insufficiency requiring artificial respiratory support. He was treated with intravenous KCl. After six hours, muscular strength had returned to normal, with plasma K+ concentration of 3.0 mmol/L. At the eighth hour, rebound hyperkalemia (6.6 mmol/L) developed with high-tented T waves, even after the KCl was discontinued. Ventilatory support was uneventfully weaned at 14 hours. Elevated free thyroxine and undetectable thyroid-stimulating hormone confirmed the diagnosis of TPP. TPP should be kept in mind as a cause of acute respiratory failure in association with acute muscle weakness to avoid delayed diagnosis and improper management.