Pre-Dialysis and Post-Dialysis Hydration Status and N-Terminal Pro-Brain Natriuretic Peptide and Survival in Haemodialysis Patients

Abstract

Purpose

Many dialysis centres have no formal program for assessing and adjusting post-haemodialysis (HD) target weight. Apart from clinical assessment, there are bioimpedance devices and natriuretic peptides that could potentially aid clinical management. We wished to determine whether pre- or post-HD bioimpedance assessment of extracellular water (ECW) or N terminal probrain natriuretic peptide (NT-proBNP) affected patient outcomes.

Methods

Multi-frequency bioimpedance assessments (MFBIA) were made before and after the midweek dialysis session, along with a post-dialysis NT-proBNP measurement.

Results

Data from 362 patients, median age of 63 (50–76) years, 59.7% male, 41.2% Caucasoid, with a median dialysis vintage of 31.4 (13.5–61.7) months were available for review. During a median follow-up of 49.6 (21.9–50.2) months there were 110 (30.4%) deaths. Patients who died had significantly increased ECW, as % over-hydrated both pre-HD 6.6 (5.8–7.6)% vs. survivors 5.1 (4–6.6)%, and post-HD 5.1 (4–6.6)% vs. 0.5 (-1-2.2.0, p<0.001, respectively. They also had higher NT-proBNP 325 (122–791) vs. 102 (48–342) pmol/l, p = 0.002. Using an adjusted Cox model, pre-HD ECW overhydration remained an independent factor associated with mortality (overhydration %: hazard ratio 1.15, 95% limits 1.03–1.28, p = 0.013), with a receiver operator curve (ROC) value of 0.7.

Conclusions

ECW excess is associated with increased mortality for HD patients, with ECW excess pre-dialysis being the strongest association, although these patients also had increased ECW post dialysis. Future trials are required to determine whether achieving euvolaemia as determined by bioimpedance improves patient survival.