Single-needle venous dialysis: a comparison of three systems

Single-needle dialysis with femoral vein access was performed on three patient groups using a pressure/time (Vital-Assist) device, a time/time device (Gambro, AK10), and a pressure/pressure device (Cobe Double Blood Pump). Each patient was dialyzed using the same parallel plate dialyzer (PPD 1.3). For each treatment, recirculation was calculated and the clearance of urea and creatinine was determined, both from dialysate content and A-V concentration differences. Recirculation was high (38%) with the Vital-Assist but under 10% with both AK10 and Double Blood Pump. The relatively higher blood flow of the Vital-Assist (180 ml/min) and lower blood flow of the AK10 (100 ml/min) resulted in comparable clearances of urea (80 ml/min) and creatinine (60 ml/min) for these two systems. The Double Blood Pump, with a blood flow of 140 ml/min achieved urea and creatinine clearances of 110 and 80 ml/min. The clearances actually measured were in good agreement with those predicted from theoretical considerations of recirculation and blood flow in a countercurrent dialysis system.