Association of Volume Status Assessed by Bioimpedance with Blood Pressure in CKD.

Abstract

Background: Hypertension is common among patients with CKD and is a risk factor for cardiovascular events and mortality. Though hypervolemia is a contributor to hypertension, the association of blood pressure with biomarkers of volume among patients with CKD is unclear.

Methods: Using data from 5,384 patients in the Chronic Renal Insufficiency Cohort (CRIC), we fit linear regression models to examine the association of vector length (bioimpedance proxy of volume) with systolic and diastolic blood pressure (BP). We employed categorical analyses given evidence of non-linear associations. We also assessed whether the change in vector length at two years from baseline was associated with changes in BP.

Results: The mean age was 59 ±11 years; 44% were female; 43% were Black; mean systolic BP and eGFR were 129 ±21 mmHg and 48 ±16 mL/min/1.73m2, respectively. The association of vector length with systolic BP was non-linear; the lowest quartile of vector length (a proxy for hypervolemia) was associated with a 3.2 mmHg (95%CI 1.1, 5.3) higher systolic BP, compared with the third quartile. Compared with the third quartile over two years, the lowest quartile of change in vector length (a proxy for volume expansion) was associated with an increase in systolic BP (3.0 mmHg; 95%CI 1.0, 5.1). Diastolic BP was not associated with vector length.

Conclusions: Shorter and shortening vector length were independently associated with higher and increasing systolic BP, respectively. Whether bioimpedance-guided optimization of volume status could improve BP management among patients with CKD requires further investigation.