Association of Volume Status Assessed by Bioimpedance with BP in CKD

Key Points Alhough hypervolemia contributes to hypertension, the association of BP with volume status measured by bioimpedance is unclear. Shorter and shortening vector length, proxies of hypervolemia, and volume expansion are associated with higher and increasing systolic BP. Bioimpedance-guided optimization of volume status may improve BP management among patients with CKD. Background Hypertension is common among patients with CKD and is a risk factor for cardiovascular events and mortality. Although hypervolemia is a contributor to hypertension, the association of BP with biomarkers of volume among patients with CKD is unclear. Methods Using data from 5384 patients in the Chronic Renal Insufficiency Cohort, we fit linear regression models to examine the association of vector length (bioimpedance proxy of volume) with systolic and diastolic BP. We used categorical analyses given evidence of nonlinear associations. We also assessed whether the change in vector length at 2 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 mm Hg and 48±16 ml/min per 1.73 m 2 , respectively. The association of vector length with systolic BP was nonlinear; the lowest quartile of vector length (a proxy for hypervolemia) was associated with a 3.2 mm Hg (95% confidence interval, 1.1 to 5.3) higher systolic BP, compared with the third quartile. Compared with the third quartile over 2 years, the lowest quartile of change in vector length (a proxy for volume expansion) was associated with an increase in systolic BP (3.0 mm Hg; 95% confidence interval, 1.0 to 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.