Dynamics of Plasma Refill Rate and Intradialytic Hypotension During Hemodialysis: Retrospective Cohort Study With Causal Methodology.

Abstract

Attaining the optimal balance between achieving adequate volume removal while preserving organ perfusion is a challenge for patients receiving maintenance hemodialysis. Current strategies to guide ultrafiltration are inadequate. We developed an approach to calculate plasma refill rate throughout hemodialysis using hematocrit and ultrafiltration data in a retrospective cohort of patients receiving maintenance hemodialysis at 17 dialysis units from January 2017-October 2019. We studied whether (1) plasma refill rate is associated with traditional risk factors for hemodynamic instability using logistic regression, (2) low starting plasma refill rate is associated with intradialytic hypotension using Cox proportional hazard regression, and (3) time-varying plasma refill rate throughout hemodialysis is associated with hypotension using marginal structural modeling. During 180,319 hemodialysis sessions among 2554 patients, plasma refill rate had high within- and between-patient variability. Female sex and hypoalbuminemia were associated with low plasma refill rate at multiple time points during the first hour of hemodialysis. Low starting plasma refill rate had higher hazards of intradialytic hypotension while high starting plasma refill rate was protective (HR 1.26, 95% CI 1.18, 1.35 versus HR 0.79, 95% CI 0.73, 0.85, respectively). However, when accounting for time-varying plasma refill rate and time-varying confounders, compared to a moderate plasma refill rate, while a consistently low plasma refill rate was associated with increased risk of hypotension (OR 1.09, 95% CI 1.02, 1.16), a consistently high plasma refill rate had a stronger association with hypotension within the next 15 minutes (OR 1.38, 95% CI 1.30, 1.45). We present a straightforward technique to quantify plasma refill that could easily integrate with devices that monitor hematocrit during hemodialysis. Our study highlights how examining patterns of plasma refill may enhance our understanding of circulatory changes during hemodialysis, an important step to understanding how current technology might be utilized to improve hemodynamic instability.