Researchers examined data on 2,750 participants aged 50 and older from three waves of the Irish Longitudinal Study on Aging who had continuous monitoring of blood pressure and cerebral oxygenation during an active stand. Nearly half (49%) of participants had supine hypertension, which researchers defined as systolic blood pressure of at least 140 mmHg and diastolic blood pressure of at least 90 mmHg.
During stand tests, participants with supine hypertension (SH) had significantly higher absolute mean arterial pressure than individuals without SH, as well as slower recovery. When cerebral oxygenation response was standardized to mean arterial BP, the response was impaired in those with SH, researchers report in Hypertension.
"Supine hypertension increased the cerebrovascular overload because of the hydrostatic pressure, resulting in the cerebral endothelial cell damage," said Dr. Kazuomi Kario, chair of cardiovascular medicine at Jichi Medical University School of Medicine in Japan.
"As the result, autoregulation of cerebral blood flow is impaired," Dr. Kario, who wasn't involved in the study, said by email.
For the active stand protocol, participants were asked to remain supine for about 10 minutes and then asked to stand as quickly as possible and remain upright for 3 minutes.
Researchers graded the severity of supine hypertension as mild (140-159 mmHg / 90-99 mmHg), moderate (160-179 mmHg / 100-109 mmHg), or severe (at least 180 mmHg / 110 mmHg).
With supine hypertension, participants had a larger initial drop in mean arterial pressure during the stand test, with larger shifts experienced with increasing severity of supine hypertension. Individuals with mild or moderate supine hypertension recovered to baseline mean arterial pressure levels at 3 minutes, but those with severe supine hypertension did not.
Lead study author Louise Newman of Trinity College Dublin didn't respond to requests for comment.
One limitation of the study is the lack of blood hemoglobin and carbon dioxide measurements, the authors note in Hypertension.
Even so, the findings as presented make some sense and seem physiologically plausible, said Dr. Raymond Townsend, director of the hypertension program at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. But currently, supine hypertension isn't routinely assessed in clinical practice, Dr. Townsend, who wasn't involved in the study, said by email.
"Virtually all our evidence, and guidance, on the management of hypertension is based on the seated blood pressure," Dr. Townsend added. "Getting clinical practices to measure the seated blood pressure properly, despite all the evidence and guidance, is still a problem, and adding a supine blood pressure would likely result in even more pushback."
SOURCE: https://bit.ly/3pYwYCC Hypertension, online June 1, 2021.
By Lisa Rapaport
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