Orthostatic/ postural hypotension

Overview

•Measured after 5 minutes supine, then at 1 and 3 minutes of standing

•Diagnostic threshold: SBP drop ≥20 mmHg (≥30 mmHg in known hypertensives) OR DBP drop ≥10 mmHg - must occur within 3 minutes of standing

🎯

The BP drop must occur within 3 minutes of standing - not immediately, and not at 5 minutes. A drop at 5 minutes does not satisfy the standard definition.

Causes

Presentation

•Lightheadedness, presyncope/syncope, visual disturbance, falls - all on standing, resolving on sitting/lying

•'Coat hanger pain' - aching in neck and shoulders from ischaemia of postural muscles

•Worse in the morning, after meals (especially carbohydrate-rich), after exercise, and in warm environments

Investigations

🥇 First-line

•lying/standing BP measurement, medication review, U&Es, FBC, glucose, TFTs, ECG

🥈 Second-line

•short Synacthen test (if adrenal insufficiency suspected), tilt table test, 24-hour ambulatory BP monitoring

Management

🥇 First-line

•medication review and rationalisation - withdraw/reduce alpha-blockers, diuretics, TCAs, antihypertensives, nitrates, levodopa where possible (single most impactful intervention)

•Adequate hydration (2-2.5 L/day) and increased dietary salt to expand intravascular volume

•Behavioural measures - rise slowly, dorsiflexion/leg crossing before standing, elevate head of bed by 10-20 degrees at night

•Compression stockings and abdominal binders - reduce venous pooling

🥈 Second-line

•fludrocortisone - synthetic mineralocorticoid, expands intravascular volume

•midodrine - alpha-1 agonist, peripheral vasoconstriction; do not take within 4 hours of bedtime (risk of supine hypertension)

⚠️

Neurogenic OH (e.g. Parkinson's disease) is often associated with supine hypertension - treating one can worsen the other. Midodrine must not be taken within 4 hours of bedtime to avoid this.