BLOOD PUMP SPEED, RECIRCULATION, AND UREA CLEARANCE IN HEMODIALYSIS PATIENTS WITH DYSFUNCTIONAL CATHETERS

Abstract

Urea clearance varies with dialysis blood pump speed (Qb) for well-functioning hemodialysis (HD) catheters. Patients with dysfunctional HD catheters often have reduced Qb due to catheter thrombosis, fibrin sheath, or central venous stenosis. One method of achieving higher Qb is to reverse the position of the HD lines (i.e., connect the arterial line to the venous port and vice versa). However, line reversal is associated with greater catheter access recirculation (AR) and resultant decreased urea clearance. Objective: To determine the effect of line reversal with varying Qb on % AR, and urea clearance in HD patients with dysfunctional. Methods: 7 patients with dysfunctional internal jugular catheters in our HD unit were identified. During a regularly scheduled HD session, we measured each patient's on-line urea clearance using dialysance (Diascan) at the maximum achievable Qb with the lines in the normal position, and at varying Qb with the lines in reversed position. With lines in the reversed position at Qb of 200, 300 and 400 ml/min, dialysance was 123, 159, and 195 ml/min respectively (figure).Conclusions: Line reversal is associated with significant AR in patients with dysfunctional catheters. However, in patients with dysfunctional HD catheters in whom the maximum achievable Qb is ≤ 200 ml/min in the normal position, greater urea clearance can be achieved by line reversal and increasing Qb to ≥ 300 ml/min. Dialysance was used as a surrogate measurement of urea clearance. AR was also measured using ultrasound dilution technique. (Transonic machine) Linear regression was used to model the relationships between Qb, dialysance and AR. Results: AR in dysfunctional IJ catheters with lines in the normal position was 0% for all Qb in the range 150–400 ml/min. According to the regression model, AR with lines in the reverse position was 19% at Qb 300 ml/min. Maximum achievable dialysance with lines in the normal position for Qb ≤ 200 ml/min was 144 ml/min.