title: Change in access blood flow over time predicts vascular access thrombosis.
abstract: BACKGROUND
  Vascular access thrombosis accounts for at least $1 billion dollars in annual expenses and 25% of hospitalizations for chronic hemodialysis patients. Low vascular access blood flow (less than 800 ml/min) has been shown to modestly increase the relative risk for thrombosis in the subsequent three months. In this study, it is hypothesized that a time-dependent decrease in vascular access blood flow may be more predictive of subsequent thrombosis especially in vascular accesses with flows more than 800 ml/min, since it would indicate the development of a critical outlet stenosis in the graft.
  
  
  METHODS
  Ninety-five accesses in 91 CHD patients were prospectively followed over 18 months. Vascular access blood flow was measured every six months by the ultrasound dilution technique. Thrombotic events were recorded during the three study periods.
  
  
  RESULTS
  A total of 34 thrombotic events in 95 accesses were documented through the total study duration. Accesses that thrombosed had a 22% decrease in vascular access blood flow during the first observation period and a further 41% decrease during the second observation period as compared to 4% drop and 15% increase during the first and second observation periods, respectively, for accesses that did not thrombose. There was an estimated 13.6-fold (95%, confidence interval 2.68 to 69.16) increase in the relative risk of thrombosis for accesses with more than 35% decrease in vascular access blood flow compared to those accesses with no change in blood flow. There was no statistical difference in the average vascular access blood flow of all patients over the study period.
  
  
  CONCLUSIONS
  Accesses that show a large (>15%) decrement in vascular access blood flow are associated with a high risk of thrombosis. Serial measurements of vascular access blood flow predict access thrombosis.
authors.affiliation: Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Neyra
authors.forename: T A
authors.initials: TA
authors.lastname: Ikizler
authors.forename: R E
authors.initials: RE
authors.lastname: May
authors.forename: J
authors.initials: J
authors.lastname: Himmelfarb
authors.forename: G
authors.initials: G
authors.lastname: Schulman
authors.forename: Y
authors.initials: Y
authors.lastname: Shyr
authors.forename: R M
authors.initials: RM
authors.lastname: Hakim
mesh_terms: D000328:Adult; D000368:Aged; D001166:Arteriovenous Shunt, Surgical / Q000009:adverse effects*; D001783:Blood Flow Velocity; D002408:Catheters, Indwelling / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011138:Polytetrafluoroethylene / Q000009:adverse effects; D011446:Prospective Studies; D006435:Renal Dialysis / Q000009:adverse effects*; D013927:Thrombosis / Q000209:etiology*
chemical_list: D011138:Polytetrafluoroethylene