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Difficulty: HardPharmacologic Interventions

A 29-year-old woman is brought to the emergency department by her sister due to profound confusion, agitation, and vomiting for the past 24 hours. The sister reports the patient was diagnosed with Graves disease two years ago but has not taken any medications for the last five months. Vital signs show a temperature of 40.2°C (104.4°F), blood pressure of 158/68 mmHg, pulse of 155/min, and respirations of 26/min. Physical examination reveals a diaphoretic, delirious patient with a diffuse, smooth, non-tender goiter, bilateral proptosis, and a fine resting tremor. Electrocardiogram demonstrates atrial fibrillation with a rapid ventricular response. A clinical diagnosis of thyroid storm is established.

Arrange the following pharmacologic interventions in the correct chronological sequence required to safely and effectively manage this patient's endocrine emergency.

  1. 1Intravenous propranolol
  2. 2Oral propylthiouracil
  3. 3Saturated solution of potassium iodide (SSKI)

Answer

The correct sequence is: 1) Intravenous propranolol, 2) Oral propylthiouracil, 3) Saturated solution of potassium iodide (SSKI).
The management of thyroid storm follows a strict, mechanism-based sequence. First, beta-blockers (propranolol) are given to achieve immediate hemodynamic stability by controlling the massive adrenergic surge. Second, a thioamide (propylthiouracil or methimazole) is administered to block the synthesis of new thyroid hormone. Finally, an iodine solution (SSKI) is given to block the release of preformed hormone. The thioamide must precede the iodine by at least one hour to prevent the iodine from being utilized as a substrate for further hormone synthesis.

Step-by-Step Solution

1
Stabilize cardiovascular function
Intravenous propranolol is given first
Beta-blockade immediately addresses the life-threatening peripheral adrenergic effects of thyroid storm (tachycardia, atrial fibrillation) and reduces peripheral T4 to T3 conversion.
2
Block new hormone synthesis
Oral propylthiouracil (PTU) is given second
PTU inhibits thyroid peroxidase, halting the production of new thyroid hormones. It must be onboard before introducing exogenous iodine.
3
Block hormone release
Saturated solution of potassium iodide (SSKI) is given third
Iodine utilizes the Wolff-Chaikoff effect to inhibit the release of preformed thyroid hormone. It is safely given 1-2 hours after PTU.

Key Concept

The sequential pharmacologic management of thyroid storm prioritizes immediate adrenergic blockade, followed by the inhibition of new hormone synthesis, and finally the inhibition of hormone release.
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Pharmacologic Interventions

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