What is the proper method for diagnosing orthostatic (low blood pressure) hypotension?

Proper Diagnosis of Orthostatic Hypotension

Orthostatic hypotension is diagnosed by measuring blood pressure after 5 minutes of lying or sitting, followed by measurements at 1 minute and 3 minutes after standing, with diagnostic criteria being a sustained drop of ≥20 mmHg systolic or ≥10 mmHg diastolic blood pressure. 1, 2

Diagnostic Criteria

• A sustained decrease in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing confirms the diagnosis. 1, 2, 3
• Alternatively, systolic BP falling to <90 mmHg within 3 minutes of standing is also diagnostic. 2
• In patients with baseline supine hypertension, use a higher threshold of ≥30 mmHg systolic drop to diagnose orthostatic hypotension. 2, 4

Step-by-Step Measurement Technique

Patient Preparation

• The patient should fast for 3 hours before testing and avoid nicotine, caffeine, theine, or taurine-containing drinks on the day of examination. 2
• Testing should occur in a temperature-controlled environment (21-23°C). 2

Measurement Protocol

• Use a validated and calibrated blood pressure device with appropriate cuff size based on arm circumference. 1, 2
• Have the patient rest in supine or sitting position for 5 minutes before baseline measurement. 1, 4
• Measure BP in both arms at the initial visit; if systolic BP differs by >10 mmHg between arms, use the arm with higher BP for all subsequent measurements. 1, 2
• Measure BP and heart rate at 1 minute and 3 minutes after standing. 1, 2, 4
• Maintain the arm at heart level during all measurements. 2

Critical Measurement Considerations

Continuous BP monitoring is superior to interval measurements for accurate diagnosis. 2, 5 Research shows that interval BP measurement devices have low concordance with continuous measurements (Lin's coefficient 0.47-0.59 for systolic and 0.33-0.42 for diastolic), resulting in missed diagnoses. 5 The positive proportion of agreement between interval and continuous measures is only 59.5%. 5

Sit-stand testing is inadequate for diagnosis. 6 A study of 730 patients demonstrated that sit-stand testing has a sensitivity of only 15.5% and specificity of 89.9% compared to head-up tilt testing, with an area under the ROC curve of just 0.564. 6

Subtypes to Recognize

Initial (Immediate) Orthostatic Hypotension

• BP decrease >40 mmHg systolic and/or >20 mmHg diastolic within 15 seconds of standing. 2
• Characterized by rapid recovery. 4

Classical Orthostatic Hypotension

• Sustained BP drop within 3 minutes of standing with a "concave" curve pattern. 1, 2

Delayed Orthostatic Hypotension

• BP drop meeting diagnostic criteria but occurring beyond 3 minutes of standing. 1, 2, 4
• Shows a slow progressive decrease in BP with more variable pattern. 1, 2
• If symptoms suggest OH but initial 3-minute testing is negative, extend standing time beyond 3 minutes. 2

Distinguishing Neurogenic from Non-Neurogenic OH

Assess the heart rate response to differentiate between neurogenic and non-neurogenic causes. 4

• Neurogenic OH: Heart rate increase <15 bpm (usually <10 bpm) indicates autonomic nervous system dysfunction. 2, 4
• Non-neurogenic OH: Adequate compensatory heart rate increase (≥15 bpm). 4

Neurogenic causes include primary autonomic failure (Parkinson's disease, multiple system atrophy) and secondary autonomic neuropathies (diabetes, amyloidosis). 2 Non-neurogenic causes include medications, dehydration, blood loss, and cardiac dysfunction. 4

When to Use Head-Up Tilt Table Testing

• If the patient cannot stand safely or clinical suspicion for OH is high despite normal bedside testing, perform head-up tilt table testing. 3, 7
• Use a 3-minute 70-degree head-up tilt following 5 minutes supine with continuous beat-to-beat plethysmography (Finometer monitoring). 6
• Tilt table testing is the reference standard for diagnosis when bedside testing is inconclusive. 6, 8

Common Pitfalls to Avoid

• Do not rely on sitting-to-standing measurements alone—they miss the majority of cases compared to supine-to-standing measurements. 6
• Do not use interval BP devices as a substitute for continuous monitoring when diagnostic accuracy is critical, as they have poor concordance. 5
• Do not measure BP only at 3 minutes—measuring at both 1 minute and 3 minutes captures initial OH that may be missed with delayed measurement. 1, 2
• Be aware that reproducibility when testing for OH is poor, so consider repeat testing if clinical suspicion remains high. 8

Screening Recommendations

• Assess for orthostatic hypotension at least at initial diagnosis of elevated BP or hypertension and thereafter if suggestive symptoms arise. 1
• In elderly hypertensive patients over 50 years old, obtain lying and standing BPs periodically. 1
• In diabetic patients, particularly after age 50, assess OH routinely due to its prognostic value for cardiovascular autonomic neuropathy. 4