Toward Automation of the Supine Pressor Test for Preeclampsia

Abstract

Preeclampsia leads to increased risk of morbidity and mortality for both mother and fetus. Most previous studies have largely neglected mechanical compression of the left renal vein by the gravid uterus as a potential mechanism. In this study, we first used a murine model to investigate the pathophysiology of left renal vein constriction. The results indicate that prolonged renal vein stenosis after 14 days can cause renal necrosis and an increase in blood pressure (BP) of roughly 30 mmHg. The second part of this study aimed to automate a diagnostic tool, known as the supine pressor test (SPT), to enable pregnant women to assess their preeclampsia development risk. A positive SPT has been previously defined as an increase of at least 20 mmHg in diastolic BP when switching between left lateral recumbent and supine positions. The results from this study established a baseline BP increase between the two body positions in nonpregnant women and demonstrated the feasibility of an autonomous SPT in pregnant women. Our results demonstrate that there is a baseline increase in BP of roughly 10-14 mmHg and that pregnant women can autonomously perform the SPT. Overall, this work in both rodents and humans suggests that (1) stenosis of the left renal vein in mice leads to elevation in BP and acute renal failure, (2) nonpregnant women experience a baseline increase in BP when they shift from left lateral recumbent to supine position, and (3) the SPT can be automated and used autonomously.

Maternal posture-physiology interactions in human pregnancy: a narrative review

“…Indeed, some studies even report changes in blood pressure with a shift in posture, with the lowest blood pressure being reached in the left lateral recumbent position ( Fagundes et al, 1992 ; Bentley-Lewis et al, 2005 ; Almeida et al, 2009 ). Recent work has implicated supine posture after 24 weeks in the development of hypertension and preeclampsia ( Tokunaga et al, 2000 ; Qureshi et al, 2019 ). At this time point, the fundus of the gravid uterus reaches the level of the renal veins, and the left renal vein at the aortic crossway is particularly vulnerable to compression in a manner similar to what is seen in nutcracker syndrome ( Reuter et al, 2016 ).…”

“…Without alternative drainage, acute renal venous outflow obstruction occurs, leading to an increase in intrarenal pressure resulting in decreased arterial perfusion and a condition akin to a renal compartment syndrome. This activates renin-mediated hypertension initially, and with repeated injury, ischemia-mediated hypertension, which may have implications in preeclampsia development ( Tokunaga et al, 2000 ; Reuter et al, 2016 ; Qureshi et al, 2019 ). Depending on severity, this may also impact the left ovarian vein and placental drainage.…”

“…Pregnancies affected by preeclampsia, perhaps as a result of widespread endothelial dysfunction, volume contraction, and sympathetic overactivity, seem to be more sensitive to the effect of posture on physiology and have aberrant responses to orthostatic stress. This work is exciting, and its results could have both diagnostic and therapeutic applications in preeclampsia ( Lewinsky and Riskin-Mashiah, 1998 ; Qureshi et al, 2019 ). We also encountered novel work relating to the possible contribution of posture to preeclampsia pathogenesis and disease activity via increased intra-abdominal pressures ( Zhang, 2015 ), compression of retroperitoneal structures including the left renal vein at the aortic crossway ( Tokunaga et al, 2000 ), and a condition dubbed, “renal compartment syndrome” ( Reuter et al, 2016 ).…”