Definition and Overview
Orthostatic hypotension (OH) is defined as a sustained reduction in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg within 3 minutes of standing or during a head-up tilt to at least 60 degrees [1].
OH affects 5-30% of elderly adults and is classified as neurogenic (autonomic failure) or non-neurogenic (volume depletion, medications, cardiac). It is an independent risk factor for falls, cognitive decline, cardiovascular events, and mortality [2].
Causes
Neurogenic OH
Results from impaired sympathetic vasoconstriction due to autonomic nervous system degeneration:
- Parkinson's disease (30-40% prevalence)
- Multiple system atrophy (severe, early feature)
- Pure autonomic failure
- Diabetic autonomic neuropathy
- Amyloid neuropathy
Non-neurogenic OH
- Volume depletion: dehydration, hemorrhage, adrenal insufficiency
- Medications: antihypertensives, diuretics, alpha-blockers, antidepressants, dopaminergic agents
- Cardiac: aortic stenosis, heart failure, arrhythmias
Symptoms
Lightheadedness, dizziness, blurred vision, weakness, fatigue, presyncope, and syncope upon standing. Symptoms may worsen after meals (postprandial hypotension), prolonged standing, dehydration, and in hot environments [3].
Some patients develop "coat hanger" pain (suboccipital and shoulder pain from ischemia of neck muscles) as a characteristic symptom of neurogenic OH.
Diagnosis
Active standing test: measure BP and heart rate supine, then at 1 and 3 minutes of standing [1].
Head-up tilt table test: standardized, reproducible assessment. Beat-to-beat BP monitoring provides continuous data.
Neurogenic vs non-neurogenic differentiation: heart rate response is key. Neurogenic OH shows blunted heart rate increase (<15 bpm). HRV analysis, plasma norepinephrine levels (supine and standing), and QSART help characterize autonomic failure [4].
Treatment
Non-pharmacological
- Increased fluid intake: 2-3 liters per day
- Increased salt intake: 6-10 grams per day (unless contraindicated)
- Compression garments: waist-high, 30-40 mmHg
- Counter-pressure maneuvers: leg crossing, squatting
- Head-of-bed elevation (10-15 degrees) to reduce supine hypertension
- Small, frequent meals to reduce postprandial hypotension
Pharmacotherapy
Fludrocortisone (0.1-0.3 mg/day): mineralocorticoid that expands plasma volume [5].
Midodrine (2.5-10 mg TID): alpha-1 agonist that increases peripheral vascular resistance. Avoid dosing within 4 hours of bedtime.
Droxidopa: norepinephrine prodrug specifically approved for neurogenic OH.
Pyridostigmine: cholinesterase inhibitor that enhances ganglionic transmission without supine hypertension.