A Stand-Up Approach to Diagnosing Orthostatic Hypotension
Although the definition of orthostatic hypotension requires that the significant drop in blood pressure observed on standing be sustained for 3 minutes (which provides evidence of true autonomic failure), clinicians who use this as a diagnostic criterion may be doing many patients a disservice. Most people who fall as a result of a drop in blood pressure do so on arising, as they get up from a bed or chair. Moreover, many hip fractures caused by falls occur in patients who experience a drop in blood pressure on standing. If patients can stand for 3 minutes without wavering or falling, their body is accommodating well.
In the clinic where I previously practiced, both sitting and standing blood pressure were measured in any patient who was taking 2 or more antihypertensive medications or psychotropic drugs, because these agents can cause significant orthostatic hypotension. Sitting and standing blood pressure were also measured in all patients older than 60 years. I am now an emergency physician, and I rarely encounter patients who have had their blood pressure taken while standing. However, I frequently find patients whose blood pressure decreases by 20 to 30 mm Hg when it is measured promptly in the erect position.
Another point to keep in mind when measuring blood pressure to confirm orthostatic hypotension is that the automatic machines may give an inaccurate reading because of the time lag required to recycle. This is especially true when the initial sitting pressure is normal and the erect finding is low. In addition, although the automatic machines are fine for patients with average-sized arms and regular rhythms, some patients do not meet these 2 criteria.
— Harold Cross, MD