Emergency Treatment of Thyrotoxic Hypokalemic Periodic Paralysis
Submitted by deb on Sat, 08/06/2011 – 23:06
A True Endocrine Emergency
Patients with Thyrotoxic Hypokalemic Periodic Paralysis typically present at the ER with an acute episode of paralysis involving the muscles of the extremities and limb girdles. The lower limbs are more frequently and severely involved than the upper. Weakness may be asymmetrical. Proximal strength is more severely impaired than distal strength. Respiratory and cardiac arrest are possible. Lie patient in coma position to avoid aspiration.
Consistent with Hypokalemia or Thyrotoxicosis; During paralysis, sinus tachycardia, diffuse ST-T changes, flattening of T waves, prolonged QT intervals, and U waves. Sinus arrest and second-degree atrioventricular block also have been described in patients with THKPP, ventricular fibrillation and ventricular tachycardia.
Elevated total thyroxine, triiodothyronine resin uptake, and total triiodothyronine levels. Radioiodine scan for Graves disease and adenomas
The mainstay of emergency treatment has always been potassium replacement, however not all patients respond to potassium alone and evidence suggests that combining potassium and propranolol is a more effective therapy, with KCl 10 mEq/h iv and/or KCl 2 g every 2 h, orally, monitoring serum K+ level, to avoid rebound hyperkalemia plus Propranolol 3–4 mg/kg, orally.
Because THKPP patients may develop rebound hyperkalemia K+ replacement therapy should be cautious and should not exceed 90 mEq of KCl per 24 hours unless there is a reason for K+ loss, such as diarrhea, vomiting or diuretic use.
In the Manoukian study (19 patients) all patients remained attack free as long as they took methimazole and propranolol hydrochloride or after radioiodine 131 treatment. Eighteen patients were eventually treated with radioiodine 131 therapy. None of the patients had paralytic episodes after a euthyroid state was achieved.
Nonselective beta-blockers such as propranolol may be useful to prevent attacks of paralysis once patients begin taking antithyroid medications but are not yet euthyroid.
For further information see:
The Man Who Couldn’t Walk: A case study of Thyrotoxic PP by Emergency Physicians
Hypokalemic Periodic Paralysis: Managing Hypokalemic Paralysis
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2. Manoukian, M.A. et al; Clinical and Metabolic Features of Thyrotoxic Periodic Paralysis in 24 Episodes. Archives of Internal Medicine Vol. 159 No. 6, March 22, 1999
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