Most orthostatic blood pressures are measured at the wrong moment

The common technique - sit the patient up, stand them, wait a couple of minutes, take one reading - misses the two patterns that matter most. Initial orthostatic hypotension happens in the first 15 to 30 seconds and has recovered by the time a two-minute cuff inflates. Delayed orthostatic hypotension appears after three minutes and is missed by anyone who has already recorded a normal value and moved on.

Measure supine after five minutes lying flat, not seated. Then stand the patient and measure at one minute and again at three, and stay with them: the fall you are looking for is 20 mmHg systolic or 10 mmHg diastolic. Ask about symptoms at each reading, because a reproduced symptom is worth more than the number, and record heart rate alongside - a fall in pressure with no compensatory rise in rate points to autonomic failure or to rate-limiting drugs rather than to volume depletion.

This matters most in exactly the patients whose antihypertensives are being escalated: older, often diabetic, frequently on an alpha blocker for prostatic symptoms that nobody has counted as a cardiovascular drug.

• Rest supine five minutes before the baseline reading, not seated
• Measure at one minute and three minutes standing, with the patient supported
• Record heart rate at each reading - a flat rate response changes the differential
• Ask about symptoms each time; a reproduced faintness matters more than the millimetres
• Count tamsulosin, tricyclics and diuretics before blaming the antihypertensive you just added

Why it matters

The measurement most units perform is timed to miss both the early and the late fall, and it is used to justify escalating treatment.

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