Orthostatic hypotension is defined by a measurement protocol, and a reading taken any other way is not the thing the definition describes. The patient lies supine for at least five minutes, the pressure is taken, and then it is taken again at one minute and at three minutes after standing — not after sitting, and not once. A fall of 20 mmHg systolic or 10 mmHg diastolic meets the definition.
The one-minute reading is the one most often skipped and the one most often abnormal. Some patients drop and recover by three minutes, so a single three-minute measurement misses them; others drop late, so a single one-minute measurement misses those. Both readings, every time.
When to do it matters as much as how. After any antihypertensive change, after any fall, in unexplained dizziness or syncope, and before adding a drug to a patient already on several. Where symptoms follow meals, measure 30 to 60 minutes after eating — postprandial hypotension is common in older people, frequently missed, and does not show up on a fasting morning reading.
And record what the patient felt, not only the numbers. A 25 mmHg drop with no symptoms and a 15 mmHg drop with presyncope are different clinical situations, and the second is the one that will produce the fall.
- Rest the patient supine for at least five minutes before the baseline reading
- Measure at one minute and at three minutes after standing — not after sitting, and not once
- Repeat the assessment after every antihypertensive change and after every fall
- Measure 30 to 60 minutes after a meal where symptoms are postprandial
- Record symptoms alongside the numbers; a smaller drop with presyncope matters more than a larger one without
Why it matters
A sitting-to-standing reading taken once is the commonest way orthostatic hypotension gets recorded as absent.
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