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Kidney Week

Abstract: SA-PO357

Does Dialysis Drive Patients to Drink?

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Adwaney, Anamika, Imperial College Healthcare NHS Trust, London, London, United Kingdom

Greater fluid intake clearly leads to greater fluid removal. But reverse causality is also possible: greater fluid removal could lead to increased thirst, causing greater fluid intake. This study uses a within-patient analysis, to examine the relationship between ultrafiltration during dialysis sessions, and weight gained during the subsequent inter-dialytic interval.


In a urban dialysis centre, a random sample of patients was selected and stratified by unit, gender and access type. Patients were eligible if they had been receiving thrice-weekly dialysis for >1yr, and were clinically stable during this period, with no hospitalisations >14days. Data were analysed within patients, as well as between patient averages. Correlations were sought between variables within patients: the number of patients with a significant within-patient linear association (p<0.05) is reported, as well as the significance of this number, as an observation from a binomial distribution with N=100,p=0.05.


From 100 patients, median(IQR) age 67(53-75) years, observed over a year, complete records were available for 15263 (98%) dialysis sessions with the subsequent inter-dialytic interval. Mean(±within-patient sd) pre-dialysis weight was 2.71(±1.15)% above target weight. Larger ultrafiltration volume was associated with greater subsequent inter-dialytic weight gain in 87/100 patients (p<0.001), and 15% of the within-patient variation in inter-dialytic weight gain was explained by variation in ultrafiltration volume at the previous dialysis session.
Lower post-dialysis weight (relative to target weight) was also associated with greater subsequent inter-dialytic weight gain in 77/100 patients (p<0.001). In addition, the rate of weight gain was dependent on the duration of the inter-dialytic interval, being 1.21(±0.53)%/day during 2-day gaps, and 1.11(±0.38)%/day during 3-day gaps (p<0.001), suggesting a non-linear pattern of fluid intake, greatest immediately after dialysis and diminishing over the course of the inter-dialytic interval.


Fluid intake in haemodialysis patients is determined by the ultrafiltration volume and end-weight of the most recent dialysis session, and diminishes during the inter-dialytic interval. Greater fluid intake is therefore a consequence, as well as a cause, of larger ultrafiltration volumes. This bidirectional relationship suggests the need to re-examine protocols for fluid removal in haemodialysis patients.