what is postural hypotension

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postural orthostatic hypotension definition causes pathophysiology

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orthostatic hypotension diagnosis symptoms management treatment

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Postural (Orthostatic) Hypotension

Postural hypotension — also called orthostatic hypotension (OH) — is defined as a drop in blood pressure upon standing up from a lying or sitting position.

Definition

A fall in:

Systolic BP > 20 mmHg, OR
Diastolic BP > 10 mmHg

...within 3 minutes of assuming an upright posture from a supine position.

(Harrison's Principles of Internal Medicine, 21st Ed., p. 6764)

Pathophysiology

When a person stands up:

Gravity causes ~500–1000 mL of blood to pool in the lower extremities and splanchnic circulation.
Normally, baroreceptors in the aortic arch and carotid sinus detect the drop in BP and trigger compensatory responses: increased heart rate, vasoconstriction, and increased cardiac output.
In postural hypotension, this compensatory reflex fails — due to autonomic dysfunction, volume depletion, or medications — resulting in sustained low BP and reduced cerebral perfusion.

A lack of compensatory tachycardia when BP drops is a key sign of autonomic insufficiency, seen in conditions like diabetes mellitus and Parkinson's disease.

Causes

Category	Examples
Autonomic dysfunction	Parkinson's disease, multiple system atrophy, diabetic neuropathy, pure autonomic failure
Volume depletion	Dehydration, hemorrhage, diarrhea, vomiting, excessive sweating
Medications	Antihypertensives, diuretics, nitrates, alpha-blockers, antidepressants (TCAs), antipsychotics, levodopa
Cardiac causes	Bradycardia, heart failure, aortic stenosis
Endocrine	Adrenal insufficiency (Addison's disease), hypothyroidism
Prolonged bed rest / deconditioning	Post-surgical patients, elderly individuals
Postprandial hypotension	After eating, especially in the elderly

Symptoms

Symptoms arise from reduced perfusion to the brain and other organs (Harrison's, p. 707):

Classic: Lightheadedness, dizziness, presyncope (near-fainting) upon standing
Non-specific: Generalized weakness, fatigue, cognitive slowing, leg buckling
Visual blurring — due to retinal or occipital lobe ischemia
"Coat-hanger headache" — pain in the suboccipital, posterior cervical, and shoulder regions, likely from neck muscle ischemia
Orthostatic dyspnea — breathlessness on standing, thought to reflect ventilation-perfusion mismatch
In severe cases: syncope (fainting) and falls

Symptoms may also be absent, making routine assessment important.

Diagnosis

Lying-to-standing BP measurement: Check BP after 5 min supine, then at 1 and 3 min after standing
Tilt-table test: For cases where active standing is not feasible
Blood tests: full blood count (anaemia), electrolytes, glucose, cortisol
ECG: to exclude cardiac arrhythmias
Review medications

Management

Non-pharmacological:

Rise slowly from lying/sitting positions
Increase fluid and salt intake (if not contraindicated)
Wear compression stockings
Elevate the head of the bed at night
Avoid triggers: prolonged standing, hot environments, alcohol, large meals
Regular physical exercise / reconditioning

Pharmacological:

Fludrocortisone — mineralocorticoid; expands blood volume
Midodrine — alpha-1 agonist; causes vasoconstriction
Pyridostigmine — enhances ganglionic transmission
Droxidopa — norepinephrine precursor (especially in neurogenic OH)
Address underlying cause (e.g., stop offending medications, treat Parkinson's, correct dehydration)

Special Considerations

Elderly patients are at highest risk due to impaired baroreflex sensitivity, polypharmacy, and reduced vascular stiffness.
Neurogenic orthostatic hypotension (from autonomic nerve damage) is often accompanied by supine hypertension, making treatment a careful balancing act.
Falls and fractures from postural hypotension are a major concern in elderly populations.

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