title: Urea clearance in dysfunctional catheters is improved by reversing the line position despite increased access recirculation.
abstract: BACKGROUND
  Problematic or dysfunctional hemodialysis (HD) catheters are routinely reversed to achieve adequate blood flow for dialysis delivery. The purpose of the study is to determine the effect of varying blood pump speed (Qb) on access recirculation (AR), and urea clearance (K) in dysfunctional catheters in the normal and reversed positions.
  
  
  METHODS
  Nineteen HD patients with tunneled cuffed catheters (5 functional and 14 dysfunctional catheters) were included; dysfunctional catheters are defined as the inability to attain a Qb of 300 mL/min or greater on 2 consecutive HD runs. AR and K measurements were obtained systematically for each catheter in the normal and reversed positions at increasing Qbs. K was measured using the ionic dialysance technique.
  
  
  RESULTS
  In functional catheters, AR in the normal position was 0% and increased to 15% +/- 13% when reversed. Dysfunctional catheters had a greater AR of 25% +/- 16% when reversed. In functional catheters, there was no evidence of an increase in AR with increasing Qb irrespective of position. Similarly, there was no relationship between increasing AR and greater Qbs (r 2 = 0.10) in dysfunctional catheters. In dysfunctional catheters, when reversed, mean K increased from 128 +/- 10 mL/min at a Qb of 200 mL/min to 157 +/- 38 mL/min at maximal Qb (P < 0.05).
  
  
  CONCLUSIONS
  We show that at increasing Qbs, K is improved in both functional and dysfunctional catheters. Data from the study are used to describe a nomogram to determine minimum Qb for a dysfunctional catheter in reversed position to maximize K.
authors.affiliation: Division of Nephrology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Carson
authors.forename: Mercedeh
authors.initials: M
authors.lastname: Kiaii
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: MacRae
mesh_terms: D000368:Aged; D000465:Algorithms; D001166:Arteriovenous Shunt, Surgical / Q000009:adverse effects*; D002408:Catheters, Indwelling / Q000009:adverse effects*; D004868:Equipment Failure; D005260:Female; D018056:Hemorheology; D006801:Humans; D007084:Iliac Vein; D007601:Jugular Veins; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D017534:Radial Artery; D006435:Renal Dialysis / Q000295:instrumentation*; D012494:Sampling Studies; D013927:Thrombosis / Q000209:etiology; D014508:Urea / Q000097:blood*; D014683:Vena Cava, Superior
chemical_list: D014508:Urea