Orthostatic Hypotension

Orthostatic hypotension (OH) is a blood-pressure failure during upright posture, not simply “feeling dizzy.” Classic OH is a sustained fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg within 3 minutes of standing, or during head-up tilt to at least 60 degrees. Standing normally shifts approximately 500–1000 mL of blood into the lower limbs and splanchnic circulation. Venous return falls, so stroke volume and cardiac output briefly decline. Arterial and cardiopulmonary baroreceptors sense the change and increase sympathetic outflow: the heart rate rises, venous capacitance vessels constrict, and systemic arterioles constrict. OH develops when this reflex response fails, as in autonomic failure, or when it is overwhelmed by inadequate circulating volume or cardiac output. The patient may describe light-headedness, visual dimming, weakness, cognitive slowing, fatigue, or a dull ache across the neck and shoulders—the “coat-hanger” ache of reduced upright perfusion. Symptoms often intensify in the morning, after meals, in heat, or after exertion. The absence of dizziness does not exclude OH; asymptomatic OH still contributes to falls and...