OH is a sustained reduction of systolic blood pressure (SBP) of ≥ 20 mm Hg or diastolic BP ≥ 10 mm Hg within 3 min of standing or head-up tilt to at least 60° on a tilt table (1). In patients with supine hypertension, a reduction in SBP of 30 mm Hg has been suggested (1).  

The Centers for Disease Control and Prevention (CDC) recommends BP measurements when patient is supine for 5 min, and after standing for 1 and 3 min (2).  In some patients symptomatic OH occurs beyond 3 minutes of standing (1). Preference for mercury column sphygmomanometer due to its reliability and simplicity, with arm at the level of the heart has been stressed (3). 

A 2017 report involving over 11,000 middle-aged participants (Atherosclerosis Risk in Communities Study) has challenged the notion of waiting 3 minutes before OH is measured (4).  This prospective study  found a significant association between participant-reported history of dizziness on standing and OH but only at 1^st measurement (mean of 28.0 seconds after standing), not at subsequent ones over a 2 minute period. It was concluded that measuring OH during the first minute “not only makes a lot of sense” but it’s more appropriate “because it’s more predictive of future falls”.

Keep in mind that OH is more common and more severe during mornings and after meals, and is exacerbated by large meals, meals high in carbohydrate, and alcohol intake (1).

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 References

1. Freeman R, Wieling W, Axelrod FB, et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Autonomic Neuroscience: Basic and Clinical 2011;161: 46–48. https://www.ncbi.nlm.nih.gov/pubmed/21431947
2. http://www.cdc.gov/steadi/pdf/measuring_orthostatic_blood_pressure-a.pdf , accessed Dec 13, 2015.
3. Naschitz J, Rosner I. Orthostatic hypotension: framework of the syndrome . Postgrad Med J 2007; 83:568-574. http://pmj.bmj.com/content/83/983/568
4. Juraschek SP, Daya N, Rawlings AM, et al. Comparison of early versus late orthostatic hypotension assessment times in middle-age adults. JAMA Intern Med 2017;1177:1316-1323. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5661881/

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