Specific Management

Propanolol 1 mg IV over 1 minute; if necessary repeat at 5-minute intervals; max. total dose 10 mg

or

Esmolol usually within range 50-200 micrograms/kg/minute

or

Metoprolol up to 5 mg at rate 12 mg/minute, repeated after 5 minutes if necessary, total dose 10-15 mg

Titrate until heart rate about 100 bpm. This helps with reducing rate related heart failure. Any betablocker can be used but only Propanolol has been shown to also prevent peripheral conversion of T4 to T3. The doses of beta blocker required may be higher than in other situations as their metabolism is increased in thyrotoxicosis.

If the patient cannot tolerate beta blockers such as those with severe asthma,, rate control can be achieved with a calcium channel blocker such as:

• Verapamil 5-10 mg over at least 2 min IV
• Diltazem 0.25 mg/kg administered over a period of 2 minutes. If the response was inadequate, a second dose of 0.35 mg/kg given over a period of 2 minutes, 15 minutes later [16].

Hydrocortisone 200 mg IV

or

Dexamethasone 2 mg IV

Steroids reduce the peripheral effects of thyroid hormones and will also treat associated hypoadrenalism if present.

Lowering circulating hormone levels

Two treatments with different actions are available. Both of these should be given however propylthiouracil should be given an hour before Lugol iodine.

In small doses iodine can lead to increased hormone production, nut in high doses (as given here) it is inhibitory and prevents its release. Propylthiouracil is given first to prevent initial iodine treatment increasing production.

Prevent synthesis

Propylthiouracil 150-300 mg PO QDS

Prevent release with iodine

Lugol iodine (5% iodine, potassium iodide 10%)10 drops daily PO.