Assessing orthostatic hypotension: Supine or seated?

When assessing for orthostatic hypotension, lying supine rather than sitting before switching to a standing position better detects orthostatic symptoms and is more predictive of falls among older adults at high risk of falls, according to the STURDY* trial presented at Hypertension 2021.

“These findings support a supine protocol for orthostatic hypotension in clinical practice,” said presenting author Dr Stephen Juraschek from Beth Israel Deaconess Medical Center, Harvard Medical School in Boston, Massachusetts, US.

According to Juraschek, the seated position is commonly used for convenience and entails a slightly shorter protocol. As most clinics routinely perform a seated blood pressure (BP) measurement anyway, it takes less time for patients to stand shortly afterward rather than getting them to lie down first before standing.

Also, it was commonly assumed that the two protocols are interchangeable, with a smaller extent of BP change seen with the seated vs the supine protocol. However, Juraschek noted that their findings showed that the physiology is quite different in general — thus raising doubts on the interchangeability between the two protocols.

Supine vs seated

The double-blind, response-adaptive STURDY trial was originally designed to study if higher doses of vitamin D3 (≥1,000 IU/day) reduced the risk of orthostatic hypotension in 522 elderly participants aged ≥70 years (mean age 76 years, 42 percent women) with low serum 25-hydroxyvitamin D at baseline who were at risk of falls. The researchers found that vitamin D supplementation did not prevent orthostatic hypotension or falls.  

During the study, orthostatic hypotension was assessed using two protocols: (i) seated to standing and (ii) supine to standing. Orthostatic hypotension was defined as a reduction of ≥20 mm Hg in systolic BP or ≥10 mm Hg for diastolic BP. [Hypertension 2021, abstract 49]

Compared with a mean BP of 129/68 mm Hg at baseline, BP increased by 3.4/2.6 mm Hg after sitting but there was a drop by 3.7/0.7 mm Hg after lying supine.

Out of 953 orthostatic BP measurements taken, orthostatic hypotension was detected in 14.8 percent of supine assessments compared with only 2.2 percent of seated assessments.

Supine assessments was better at predicting falls (hazard ratio [HR], 1.60; p=0.06) compared with seated assessments (HR, 0.70; p=0.39). Although both did not achieve statistical significance, the association with risk of fall was stronger for supine than seated protocols, reported Juraschek.

Furthermore, supine orthostatic hypotension was significantly associated with an increased risk of orthostatic symptoms such as fainting, room spinning, blacking out, seeing spots, and headache in the past 30 days (p=0.048 to 0.002). In contrast, no such association was seen with seated orthostatic hypotension.

“Supine orthostatic hypotension was more prevalent and appeared to better predict falls and orthostatic symptoms than seated orthostatic hypotension,” concluded Juraschek, who called for a change to supine assessments for orthostatic hypotension in current practice. 

*STURDY: Study to Understand Fall Reduction and Vitamin D in You