A 60-year-old man in septic shock requires escalating norepinephrine infusions despite adequate fluid resuscitation. Random cortisol is measured at 4 µg/dL. Hydrocortisone is given and his vasopressor requirement falls within hours. What physiologic property of cortisol explains this rapid improvement?
- A Inhibition of antidiuretic hormone secretion promoting diuresis
- B Mineralocorticoid activity restoring effective circulating volume
- C Permissive effect maintaining vascular responsiveness to catecholamines ✓
- D Direct positive inotropic action on cardiac myocytes
Correct answer: C. Permissive effect maintaining vascular responsiveness to catecholamines
Explanation
Cortisol is required for blood vessels to respond normally to catecholamines; it upregulates adrenergic receptor signaling and prevents nitric oxide-mediated vasoplegia. In its absence, pressors fail and hypotension becomes refractory, which is why stress-dose hydrocortisone is given in catecholamine-resistant shock. The mineralocorticoid effect of hydrocortisone contributes little acutely, and cortisol has no direct inotropic action.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
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