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Difficulty: HardPharmacologic Interventions

A 2828-year-old woman is brought to the emergency department by her husband due to severe agitation, confusion, and palpitations. She has a history of Graves disease but has been nonadherent to her medications for the past three months. One week ago, she was treated for a urinary tract infection. Her temperature is 39.8∘C39.8^\circ\text{C} (103.6∘F103.6^\circ\text{F}), blood pressure is 160/70 mm Hg160/70\text{ mm Hg}, and pulse is 145 /min145\text{ /min} and irregular. Physical examination reveals profuse diaphoresis, a fine resting tremor, and a diffusely enlarged, non-tender thyroid gland. An electrocardiogram demonstrates atrial fibrillation with a rapid ventricular response. The patient is diagnosed with thyroid storm.

Arrange the following pharmacologic interventions in the correct sequential order of administration for the safe and optimal management of this patient's condition.

  1. 1Intravenous propranolol
  2. 2Oral propylthiouracil
  3. 3Potassium iodide solution

Answer

The correct sequential order is: 1. Intravenous propranolol, 2. Oral propylthiouracil, 3. Potassium iodide solution.
The optimal management of thyroid storm follows a strict mechanistic sequence designed to stabilize the patient while preventing exacerbation of the hyperthyroid state. Intravenous propranolol is given first to rapidly mitigate life-threatening adrenergic symptoms and decrease peripheral T4 to T3 conversion. Oral propylthiouracil is given next to inhibit thyroid peroxidase and stop new hormone synthesis. Finally, potassium iodide is given at least one hour after propylthiouracil to block the release of preformed thyroid hormone (Wolff-Chaikoff effect).

Step-by-Step Solution

1
Administer intravenous propranolol.
Rapid control of sympathetic hyperactivity and reduction of peripheral conversion of T4 to T3.
Cardiovascular compromise (e.g., atrial fibrillation with rapid ventricular response) is the most immediate life-threatening manifestation of thyroid storm and requires rapid stabilization before targeting the thyroid gland directly.
2
Administer oral propylthiouracil.
Inhibition of thyroid peroxidase, halting de novo thyroid hormone synthesis.
Hormone synthesis must be completely blocked before exogenous iodine is introduced to prevent the gland from using the new iodine substrate to make more hormone.
3
Administer potassium iodide solution.
Inhibition of the release of preformed thyroid hormone (Wolff-Chaikoff effect).
Once synthesis is blocked (typically waiting 1 hour after thionamide administration), iodine safely blocks the release of stored hormone into the circulation without fueling further thyrotoxicosis.

Key Concept

In thyroid storm, the correct pharmacologic sequence is beta-blockade for immediate cardiovascular stabilization, followed by a thionamide to block new hormone synthesis, and finally iodine (delayed by at least 1 hour) to block hormone release.
Estimated Time:1m 30s
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Pharmacologic Interventions

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