Even a Moderate Fluid Removal Rate during Individualised Haemodialysis Session Times Is Associated with Decreased Patient Survival

Abstract

Background: Several studies report that fluid removal rate (FRR) above 10-13 mL/h/kg is associated with increased mortality in haemodialysis (HD) patients.

Aim: The aims of this study are to assess the influence of moderate FRR on survival in a cohort of prevalent dialysis patients with various dialysis session times and to challenge the FRR thresholds associated with increased mortality risk reported previously.

Methods: Interdialytic weight gain (IDWG) and FRR (calculated from ultrafiltration [UF], target weight, and session time prescriptions) were studied in 190 prevalent dialysis patients (female: 42%, mean age: 69.5 years, median vintage: 40.2 months, diabetes: 34.7%, loop diuretic prescription: 5.8%) and averaged during the final quarter of 2010. Patient survival was analysed using Kaplan-Meier and Cox-multivariate analyses.

Results: The median IDWG, median session time, and median FRR were 2.33 kg (-0.54-4.57), 5.0 h (3.9-8.0 h), 6.8 mL/h/kg (1.3-16.7), respectively, and FRR was ≥10 mL/h/kg in 11.6% of the patients. The Kaplan-Meier analysis showed decreased patient survival when the FRR was above the median (6.8 mL/h/kg; p = 0.012). The FRR was found to be independently associated with increased mortality (hazard ratio 1.15 [95% CI 1.02-1.29]; p = 0.027) using stepwise Cox proportional hazard regression analysis, including age, vintage, gender, body mass index (BMI), serum albumin level, β2-microglobulin level, cardiovascular and diabetes history, and session time. Online haemodiafiltration did not change this result. The role of residual renal function was unlikely because 74% of the patients had a vintage of >18 months, a minority (5.8%) were prescribed loop diuretics (a surrogate of significant urine output) and β2-microglobulin level was not different in patients who were below or above the FRR median.

Conclusion: We concluded that the FRR threshold above which there is an increased mortality is lower than what has been reported (7.8 mL/h/kg). It raises the question of the hazard of fluid removal and intermittence of standard HD.

Keywords: Fluid removal rate; Haemodialysis; Outcomes; Residual renal function; Survival; Ultrafiltration.