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Difficulty: MediumPharmacologic Interventions

A 28-year-old woman is brought to the emergency department with severe agitation, palpitations, and confusion. She has a history of Graves disease but has not taken her antithyroid medications for the past three months. Her temperature is 39.8°C (103.6°F), blood pressure is 150/70 mmHg, and heart rate is 145/min and irregular. Physical examination reveals diaphoresis, a fine resting tremor, and a diffusely enlarged, non-tender thyroid gland with a prominent bruit. An electrocardiogram shows atrial fibrillation with a rapid ventricular response. A clinical diagnosis of thyroid storm is established.

Arrange the following pharmacologic interventions in the most appropriate chronological order of administration for managing this patient's condition.

  1. 1Administer intravenous propranolol
  2. 2Administer oral propylthiouracil (PTU)
  3. 3Administer oral potassium iodide
  4. 4Refer for radioactive iodine ablation

Answer

The correct sequence is to first administer intravenous propranolol, followed by oral propylthiouracil, then oral potassium iodide, and finally refer for radioactive iodine ablation after stabilization.
The correct pharmacological sequence for thyroid storm prioritizes life-saving hemodynamic control with beta-blockers, followed by cessation of hormone synthesis using thionamides, followed by cessation of hormone release using iodine, and eventually concludes with long-term definitive therapy once the acute episode has resolved.

Step-by-Step Solution

1
Stabilize hemodynamics and control adrenergic symptoms.
Intravenous propranolol is administered.
Immediate beta-blockade is required to reduce the life-threatening extreme tachycardia and autonomic hyperactivity, while also partially blocking peripheral conversion of T4 to T3.
2
Block new thyroid hormone synthesis.
Oral propylthiouracil (PTU) is administered.
Before the thyroid gland is exposed to high doses of iodine (which would fuel further synthesis), the cellular machinery for synthesizing new hormone must be shut down.
3
Block the release of preformed thyroid hormone.
Oral potassium iodide is administered at least 1 hour after PTU.
The sudden iodine load rapidly inhibits the proteolytic release of T3 and T4 from thyroglobulin (Wolff-Chaikoff effect), rapidly lowering serum hormone levels.
4
Provide long-term definitive therapy.
The patient is referred for radioactive iodine ablation.
Once the acute crisis is fully resolved and the patient returns to a euthyroid state, definitive therapy is planned to prevent future recurrences.

Key Concept

The sequential pharmacologic management of thyroid storm dictates that autonomic control is established first, and thionamides must be given prior to iodine to prevent substrate loading and subsequent exacerbation of thyrotoxicosis.
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Pharmacologic Interventions

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