Orthostatic Hypotension

Orthostatic hypotension is defined as a sustained drop of ≥20 mmHg in systolic blood pressure or ≥10 mmHg in diastolic blood pressure within 3 minutes of moving from supine to standing.

The definition requires a postural change. A single seated blood pressure reading does not capture it. Lying and standing measurements — taken in sequence with appropriate timing — are the diagnostic standard.

This is the most common reason orthostatic hypotension is missed in clinical practice: it requires looking for it. A patient who reports lightheadedness on standing, near-syncope, or falls may have a normal seated blood pressure and a clinically significant postural drop that was never measured.

When blood pressure drops on standing, the normal compensatory response is a rise in heart rate. The sympathetic nervous system detects the drop in venous return and cardiac output and increases heart rate to compensate.

A compensatory tachycardia — heart rate rising 15–20 bpm or more on standing — suggests volume depletion or deconditioning. The autonomic system is intact and responding. The problem is the volume or the vascular tone.

A blunted or absent heart rate rise — blood pressure drops but heart rate does not increase appropriately — suggests autonomic failure. The nervous system cannot mount the compensatory response. This is neurogenic orthostatic hypotension.

These two mechanisms have different causes and different management. The heart rate response is the branch point.

Volume depletion is the most common reversible cause of orthostatic hypotension. Dehydration, poor oral intake, vomiting, diarrhea, diuretic use, and hemorrhage all reduce intravascular volume and impair the postural blood pressure response.

The clinical picture typically includes a compensatory tachycardia on standing, dry mucous membranes, reduced skin turgor, and a history consistent with volume loss.

Rehydration — oral or intravenous depending on severity — corrects the orthostatic hypotension when volume depletion is the primary driver. The blood pressure and heart rate response normalize as volume is restored.

A significant proportion of clinically encountered orthostatic hypotension has a pharmacologic contributor. The medication review belongs early in the evaluation.

Antihypertensives reduce vascular tone and blunt the blood pressure response to standing. Diuretics reduce intravascular volume. Alpha-blockers impair peripheral vasoconstriction. Nitrates cause venodilation and reduce preload. Tricyclic antidepressants have alpha-blocking properties. Dopamine agonists — used in Parkinson disease — impair sympathetic vasoconstriction.

Identifying and adjusting the offending agent may resolve the orthostatic hypotension without additional intervention. Dose reduction, timing changes, or substitution with an agent that has less postural effect are all reasonable approaches depending on the clinical context.

Neurogenic orthostatic hypotension arises from autonomic failure — the nervous system cannot mount the normal compensatory response to standing. Volume repletion alone does not correct it.

Common causes include diabetic autonomic neuropathy, Parkinson disease, multiple system atrophy, and pure autonomic failure. These conditions impair the sympathetic vasoconstriction and heart rate response that normally maintain blood pressure on standing.

The clinical signature is a blood pressure drop on standing without a compensatory rise in heart rate. Management focuses on non-pharmacologic measures — head-of-bed elevation, compression garments, increased salt and fluid intake, small frequent meals — and pharmacologic options when non-pharmacologic measures are insufficient.

Supine hypertension is a common comorbidity in neurogenic orthostatic hypotension. Managing both simultaneously requires careful titration.

For volume-depleted orthostatic hypotension, the primary intervention is volume repletion — oral hydration if tolerated, IV isotonic fluids if the deficit is significant or oral intake is inadequate. Identifying and correcting the source of volume loss (bleeding, GI losses, diuretic excess, poor intake) is essential.

Medication review is the most impactful intervention for drug-induced orthostatic hypotension. Reducing or eliminating the offending agent — antihypertensives, diuretics, alpha-blockers, tricyclics, antipsychotics — often resolves the problem. Dose timing adjustments (e.g., taking antihypertensives at bedtime) can reduce the clinical impact without full discontinuation.

Non-pharmacologic measures apply to all causes and should be implemented before adding medications. These include: rising slowly from supine to sitting to standing, sleeping with the head of the bed elevated 10–20 degrees (reduces nocturnal natriuresis), compression stockings and abdominal binders (reduce venous pooling), increased sodium and fluid intake (2–3 L/day) in patients without contraindications, and avoiding large carbohydrate-heavy meals.

Pharmacologic options for neurogenic orthostatic hypotension when non-pharmacologic measures are insufficient: fludrocortisone (a mineralocorticoid that expands plasma volume) and midodrine (a peripheral alpha-1 agonist that increases vascular tone). Both require monitoring — fludrocortisone for hypokalemia and supine hypertension, midodrine for supine hypertension and urinary retention. Droxidopa is an option specifically for neurogenic orthostatic hypotension associated with Parkinson disease and related syndromes.

Expected course: volume-depleted and medication-induced orthostatic hypotension typically resolves with correction of the underlying cause. Neurogenic orthostatic hypotension is generally chronic and requires ongoing management. Falls risk assessment and modification of the home environment are important components of care in older adults.

Escalation: new orthostatic hypotension with syncope, recurrent falls, or no identifiable reversible cause warrants further evaluation. Autonomic testing and neurology consultation are appropriate when neurogenic orthostatic hypotension is suspected. Cardiology consultation is appropriate when cardiac causes (arrhythmia, structural disease) are suspected.