title: Noninvasive transcutaneous access flow measurement before and after hemodialysis: impact of hematocrit and blood pressure.
abstract: OBJECTIVE
  The dialysis outcome is strongly affected by the function of the vascular access. It has been suggested that access clotting may be related to increased hematocrit (Hct) or excessive ultrafiltration during dialysis. The present study was designed to evaluate the changes of vascular access flow during hemodialysis in 18 end-stage renal disease patients with native arteriovenous fistulas and the possible correlations with Hct and mean arterial pressure (MAP).
  
  
  METHODS
  We utilized a noninvasive vascular access flow measurement technique, based on a transcutaneous optical sensor, to evaluate the flow in the access before and after a single hemodialysis session. At the beginning and at the end of the session, the blood flow was measured noninvasively, placing the sensor approximately 2 in from the point of insertion of the arterial needle. At the same time, Hct and MAP were measured directly. All patients were on hemodialysis for more than 3 months.
  
  
  RESULTS
  There was a significant increase in Hct, likely due to ultrafiltration and consequent hemoconcentration, from the beginning to the end of the dialysis session. In detail, the Hct increased from 32.6 +/- 1.9 to 35.4 +/- 1.8% (p < 0.001), while the MAP did not present significant variations. The blood flow did not show significant variations, increasing from 780 +/- 312 to 919 +/- 411 ml/min after the session. Because of the stability of the MAP, we could dissociate the effects of the Hct from those of the MAP on blood flow variations.
  
  
  CONCLUSIONS
  Our study suggests that the blood flow in native fistulas is not affected by the acute rise in Hct due to ultrafiltration during hemodialysis. The transcutaneous access flow measurement technique appears to be reliable and accurate, and it could represent an important diagnostic tool.
authors.affiliation: Department of Nephrology, St. Bortolo Hospital, Vicenza, Italy. cronco@goldnet.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Ronco
authors.forename: Alessandra
authors.initials: A
authors.lastname: Brendolan
authors.forename: Carlo
authors.initials: C
authors.lastname: Crepaldi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: D'Intini
authors.forename: Olga
authors.initials: O
authors.lastname: Sergeyeva
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Levin
mesh_terms: D001164:Arteriovenous Fistula; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002408:Catheters, Indwelling; D004867:Equipment Design; D005260:Female; D006400:Hematocrit; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy; D008297:Male; D006435:Renal Dialysis / Q000295:instrumentation* / Q000379:methods