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Difficulty: HardPharmacologic Interventions

A 34-year-old woman with a history of Graves disease is brought to the emergency department by her family due to fever, severe agitation, and palpitations over the past 24 hours. She recently had an upper respiratory tract infection. Temperature is 39.8°C (103.6°F), pulse is 152/min, respirations are 24/min, and blood pressure is 150/90 mm Hg. She appears delirious and is profusely diaphoretic. Physical examination reveals a symmetrically enlarged, non-tender thyroid gland and a fine resting tremor. Electrocardiogram demonstrates marked sinus tachycardia. A presumptive diagnosis of thyroid storm is made. Supportive care with intravenous fluids and external cooling is initiated.

Arrange the following targeted pharmacologic interventions in the correct chronological sequence to safely and effectively manage this patient's condition, starting with the most immediate intervention.

  1. 1Administer intravenous propranolol
  2. 2Administer oral propylthiouracil
  3. 3Administer saturated solution of potassium iodide
  4. 4Administer radioactive iodine (I-131)

Answer

The correct sequence of pharmacologic interventions is: intravenous propranolol, followed by oral propylthiouracil, followed by saturated solution of potassium iodide, and eventually radioactive iodine (I-131) once the crisis has resolved.
The correct sequence is dictated by the physiological mechanism of thyroid storm and the pharmacodynamics of the treatments. Life-threatening sympathetic symptoms are immediately neutralized with beta-blockers. Next, the synthesis of new thyroid hormone is halted with a thionamide. Once synthesis is blocked, it is safe to administer an iodine solution to halt the release of preformed hormone. Definitive ablation is reserved for the outpatient setting once the patient has fully recovered.

Step-by-Step Solution

1
Control systemic adrenergic tone.
Intravenous propranolol is administered.
Provides immediate mitigation of cardiovascular collapse and severe symptomatic hyperactivity, while also decreasing peripheral conversion of T4 to T3.
2
Block new hormone synthesis.
Oral propylthiouracil (or methimazole) is given.
Stops the production of new T3 and T4 within the thyroid gland, which must occur prior to introducing exogenous iodine.
3
Block release of preformed hormone.
Saturated solution of potassium iodide is administered at least 1 hour later.
Halts the release of stored hormone via the Wolff-Chaikoff effect; waiting prevents the iodine from being utilized as a substrate to synthesize massive amounts of new hormone.
4
Provide definitive curative therapy.
Radioactive iodine (I-131) ablation is scheduled for the future.
Curative therapy is absolutely contraindicated during the acute storm as radiation thyroiditis can release stored hormone and worsen the condition; it requires a stable, euthyroid state.

Key Concept

The precise sequence for managing thyroid storm requires blocking sympathetic outflow, followed by blocking new hormone synthesis, and only then blocking hormone release to prevent exacerbating the crisis.
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Pharmacologic Interventions

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