Baroreflex sensitivity is reduced in elderly hypertensive patients. Which consequence of impaired baroreflex function most directly causes orthostatic hypotension in this population?

• A Inadequate sympathetic vasoconstriction and heart rate increase on standing leads to blood pooling in lower extremities and falling BP ✓
• B Reduced arterial wall stiffness means baroreceptors are excessively stimulated when standing
• C Excess renin release on standing causes acute vasoconstriction and syncope
• D Parasympathetic overactivity causes bradycardia and hypotension on standing

Explanation

The baroreflex normally detects the drop in venous return and arterial pressure when standing and activates sympathetic vasoconstriction and tachycardia within seconds to maintain BP. In elderly patients with hypertension, arterial stiffness reduces carotid sinus wall deformation per unit pressure change (impaired mechanosensing), and downstream sympathetic responses are blunted. Without adequate vasoconstriction of splanchnic and lower limb vessels and compensatory tachycardia, blood pools in dependent vessels → cerebral hypoperfusion → orthostatic hypotension and syncope. This is worsened by antihypertensives, dehydration, and autonomic neuropathy.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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