Inflow time and recirculation in single-needle hemodialysis

Abstract

The recirculation of previously dialyzed blood in the lumen of the single-needle catheter reduces dialysis efficiency and is a drawback of single-needle dialysis. We reasoned that using maneuvers that would augment the volume of blood drawn in during the inflow phase of each dialytic cycle would decrease recirculation. We tested this hypothesis by progressively lengthening the inflow time and measuring the recirculation rate in three patients undergoing single-needle hemodialysis with a single-lumen subclavian hemodialysis catheter during five separate dialyses. Inflow time was varied with a time-time single-needle device (Gambro SN-10-2D). Percentage recirculation decreased progressively from 23% +/- 3% at an inflow time of 1 second to 7% +/- 2% at an inflow time of 4 seconds (P less than .03, n = 5). With a time-time single-needle device, recirculation did not vary, with a change in pump speed from 106 to 250 mL/min (8.2% v 8.4%, n = 6). With other single-needle devices, however, inflow time varied inversely with pump speed, and at higher pump speeds, recirculation tended to increase, although not uniformly, in every patient. Maximizing the inflow volume is essential for minimizing recirculation in single-needle hemodialysis. Clinically insignificant recirculation ensues when inflow time is maintained between 3 to 5 seconds and time-time single-needle devices are used, even in patients dialyzed with single-lumen subclavian catheters.