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Difficulty: Very hardGeneral Internal Medicine

A 65-year-old man is brought to the emergency department by his wife due to worsening confusion, weakness, and fatigue over the past 24 hours. He has a history of a nonfunctioning pituitary macroadenoma treated with transsphenoidal resection and radiation therapy 3 years ago, chronic obstructive pulmonary disease (COPD), and heart failure with preserved ejection fraction. Four days ago, he was diagnosed with a mild COPD exacerbation at an urgent care clinic and was prescribed a 5-day course of azithromycin. Today, his temperature is 36.1°C (97.0°F), blood pressure is 88/54 mm Hg, pulse is 110/min, and respirations are 24/min. Pulse oximetry is 93% on room air. Physical examination shows a lethargic man who follows simple commands. Jugular venous pressure is 6 cm H2OH_2O. Chest auscultation reveals distant breath sounds and scattered end-expiratory wheezes unchanged from his baseline. Heart sounds are normal. The extremities are cool without edema. Laboratory studies show:

Sodium: 131 mEq/L
Potassium: 3.9 mEq/L
Chloride: 98 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 42 mg/dL
Creatinine: 1.8 mg/dL
Glucose: 62 mg/dL
Thyroid-stimulating hormone: 0.2 µU/mL (Normal: 0.4-4.0 µU/mL)
Free T4: 0.6 ng/dL (Normal: 0.9-1.7 ng/dL)

Arterial blood gas analysis on room air reveals:
pH: 7.31
PaCO2: 29 mm Hg
PaO2: 78 mm Hg

Which of the following is the most appropriate next step in management?

  1. A
    Initiate noninvasive positive-pressure ventilation
  2. B
    Switch azithromycin to intravenous piperacillin-tazobactam
  3. Administer intravenous hydrocortisoneAnswer
  4. D
    Administer intravenous levothyroxine
  5. E
    Administer intravenous furosemide

Answer

Administer intravenous hydrocortisone
The correct answer addresses the patient's acute adrenal crisis. The clinical presentation of hypotension, hypoglycemia, and lethargy in a patient with a history of pituitary irradiation is highly suspicious for panhypopituitarism. The laboratory findings of a low TSH and low free T4 confirm central hypothyroidism, which almost certainly means the patient has concurrent central adrenal insufficiency. In any patient with suspected secondary adrenal insufficiency and hypothyroidism, intravenous glucocorticoids (such as hydrocortisone) must be administered prior to thyroid hormone replacement. This is because thyroid hormone increases the basal metabolic rate and accelerates the hepatic clearance of cortisol. If levothyroxine is given first, it can rapidly deplete any remaining circulating cortisol, precipitating a life-threatening adrenal crisis.

Step-by-Step Solution

1
Evaluate the patient's hemodynamic status, metabolic panel, and arterial blood gas.
The patient is in distributive shock with hypoglycemia, hyponatremia, and a high anion gap metabolic acidosis (AG=19AG = 19). Winter's formula (1.5×14+8=291.5 \times 14 + 8 = 29) confirms perfect respiratory compensation.
To rule out uncompensated respiratory failure or cardiogenic shock, which would demand immediate ventilatory or diuretic support.
2
Analyze the thyroid function tests in the context of the patient's past medical history.
Low TSH and low free T4 indicate central hypothyroidism, which, combined with the history of pituitary irradiation, strongly suggests panhypopituitarism.
To identify the underlying etiology of the distributive shock and hypoglycemia, which points to an acute adrenal crisis.
3
Determine the appropriate pharmacological sequencing for treating central hypothyroidism and concurrent adrenal insufficiency.
Intravenous hydrocortisone must be administered before levothyroxine.
Administering thyroid hormone first accelerates hepatic metabolism of cortisol, which can precipitate or fatally worsen an adrenal crisis.

Key Concept

In patients with suspected panhypopituitarism presenting with concurrent central adrenal insufficiency and central hypothyroidism, glucocorticoids must be administered before thyroid hormone replacement to prevent precipitating a fatal adrenal crisis.
Estimated Time:2m 0s
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General Internal Medicine

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