Risk factors for increased variability in dialysis delivery in haemodialysis patients.

Background. Numerous events may occur during a haemodialysis session, leading to variation in the quantity of dialysis received. The purpose of this study was to identify risk factors for variability in haemodialysis delivery. Methods. Variability in dialysis delivery was expressed by the coefficient of variation (CV%) and calculated for the volume of blood processed (VBP) for all treatments and the monthly urea reduction ratio (URR) in each patient over an 8 month period. The univariate and multivariate relationships between various predictor variables and the URR and VBP CV% were determined. Results. Eighty-nine patients were identified who met study criteria. The mean VBP and URR CV% were 10.3 +/- 4.7 and 5.4 +/- 3.8%, respectively. Patients with tunnelled catheters and total nursing-care patients had higher VBP and URR CV%, as evaluated by multivariate analysis. Patients with inadequate dialysis (mean URR < 65%) had a higher VBP CV% than those patients with mean URR values greater than or equal to65% (14.8 +/- 5.4 vs 9.7 +/- 4.5 %; P = 0.01). An accurate determination of the URR in 90% of patients required 14 measurements in patients with catheters vs three and two measurements in arteriovenous fistulae and polytetrafluoroethylene grafts, respectively. Conclusions. This study demonstrated that the use of a venous tunnelled catheter and dialysis in a total nursing-care unit were the only factors independently associated with greater variability in both VBP and URR. Attention to individual dialysis sessions in patients with tunnelled catheters or in a total nursing-care unit is prudent, particularly when identifying reasons for under-dialysis.