Optimizing Dialysis Delivery in Tunneled Dialysis Catheters

Long-term dialysis is often delivered through tunneled central venous catheters (CVC) despite their associated morbidity and mortality rates. Because poor solute clearance might contribute to this risk, we examined the relation between blood pump speed (QB), access recirculation (AR), and dialysis delivery in patients with CVC. We conducted a prospective study on 102 patients receiving long-term hemodialysis with CVC. QB was systematically varied, and AR was measured by saline dilution with the blood supply lines in both the straight and the reversed positions during each of two dialysis sessions. During a third session, we measured ionic dialysance (EID) in patients with AR>0% and those in whom dialysis was usually delivered with catheters in the reversed position.Approximately one third (34.3%) of patients were usually run in the reversed position. Clinically significant AR (>10%) was infrequent (3%) in the straight position but common in the reversed position (86%). QB and EID were linearly correlated for both the straight and reversed positions. Approximately half (48.6%) of patients who were generally treated with their lines reversed were able to receive dialysis with the lines in the straight position within acceptable pressure limits when blood lines were switched part way through the run. In these patients, solute clearance was equivalent (EID straight 204 ml/min vs. reversed 196 ml/min, p=0.58) with lines in the straight configuration despite lower achieved QB (straight 354 ml/min vs. reversed 404 ml/min, p=0.04). Maximization of prescribed QB in CVC increased AR when blood line position was reversed but improved small solute clearance regardless of line position. This suggests that QB in CVC should be set as high as circuit pressure limits will allow, regardless of the potential for AR, and that reversal of line position confers no benefit with respect to solute clearance.