Association of objective measures of volume status with blood pressure, cardiac structure, and cardiac function among patients receiving maintenance hemodialysis

Abstract

Background Intradialytic hypertension, defined as an increase in BP from pre- to post-hemodialysis (HD), affects 5%–15% of patients receiving maintenance HD and is associated with cardiovascular and all-cause mortality. Hypervolemia is believed to be a major etiological factor, yet the association of more objective biomarkers of volume status with intradialytic hypertension is not well described. Methods In a post hoc analysis of the Frequent Hemodialysis Network Daily Trial (n5234), using data from baseline, 1-, 4-, and 12-month visits (n5800), we used random-effects regression to assess the association of bioimpedance estimates of volume (vector length) with post-HD systolic BP (continuous) and any increase in systolic BP (categorical) from pre- to post-HD. We adjusted models for randomized group; age; sex; self-reported race; Quételet (body mass) index; vascular access; HD vintage; hypertension; history of heart failure; diabetes; residual kidney function (urea clearance); pre-HD systolic BP; ultrafiltration rate; serum-dialysate sodium gradient; and baseline values of hemoglobin, phosphate, and equilibrated Kt/V urea. Results The mean age of participants was 50614 years, 39% were female, and 43% were Black. In adjusted models, shorter vector length (per 50 V/m) was associated with higher post-HD systolic BP (2.9 mm Hg; 95% confidence interval [CI], 1.6 to 4.3) and higher odds of intradialytic hypertension (odds ratio 1.66; 95% CI, 1.07 to 2.55). Similar patterns of association were noted with a more stringent definition of intradialytic hypertension (.10 mm Hg increase from pre- to post-HD systolic BP), where shorter vector length (per 50 V/m) was associated with a higher odds of intradialytic hypertension (odds ratio 2.17; 95% CI, 0.88 to 5.36). Conclusions Shorter vector length, a bioimpedance-derived proxy of hypervolemia, was independently associated with higher post-HD systolic BP and risk of intradialytic hypertension.