Effects of Pre-Dialysis Fluid Overload, Intradialytic Relative Blood Volume Levels and Cumulative Ultrafiltration Volume on Pulse Wave-Derived Features during Hemodialysis: Results from a Longitudinal Cohort Study

INTRODUCTION: Arterial pulse wave features (PWFs) reflect hemodynamic changes during hemodialysis and, while their use is not currently recommended by clinical practice guidelines, many PWFs are associated with patient outcomes beyond classical blood pressure measurements. Pre-dialysis fluid overload (FO), intradialytic relative blood volume (RBV), and cumulative ultrafiltration volume (cUFV) may influence PWFs, but these relationships remain incompletely characterized. We aimed to explore associations between FO, RBV, cUFV, and PWFs during hemodialysis. METHODS: We analyzed 79 hemodialysis sessions in 24 patients over five weeks. Each session included pre-dialysis bioimpedance spectroscopy, cuff-based pulse wave measurements every 15 minutes, and continuous RBV/cUFV monitoring. Associations between RBV or cUFV and 28 PWFs (including blood pressure measures, parameters of cardiac function, and various arterial wave features derived from pulse wave analysis) were assessed using confounder-adjusted generalized estimating equations. Repeated-measures correlation analysis evaluated within-patient associations between pre-dialysis FO and both initial PWF levels (median from the first 45 minutes) and their intradialytic changes (late minus early 45-minute median). RESULTS: We analyzed 817 pulse wave measurements from 24 patients (21 men; median age 66 years). RBV was associated with 18/28 PWFs (64%), whereas cUFV was associated with 10/28 (36%), with distinct patterns: associations with RBV were observed mainly for the cardiac function parameters (stroke volume, cardiac output, heart rate) and arterial wave components (forward/backward wave amplitudes, wave intensity peaks, reflection coefficient), while associations with cUFV were observed mainly for diastolic blood pressure, peripheral resistance, and reservoir pressure. Significant early-to-late intradialytic changes in PWFs included a decrease in stroke volume, reflection coefficient and cardiac output, as well as an increase in pulse pressure amplification and reflected intensity peak. Among initial PWF levels, only the excess pressure integral correlated with pre-dialysis FO; however, FO correlated positively with intradialytic changes in systolic and mean blood pressure, pulse wave velocity, and reservoir pressure, indicating attenuated decreases in these parameters when baseline fluid excess was higher. CONCLUSION: In the studied cohort, RBV and cUFV showed distinct association profiles with PWFs during hemodialysis. These relationships warrant consideration in studies assessing or intervening on PWFs in dialysis patients.