title: Duplex ultrasound volumetric flow analysis before and after hemodialysis in patients with brachio-cephalic fistulae.
abstract: OBJECTIVE
  The United Kingdom Renal Association recommends duplex ultrasound to monitor arteriovenous fistula (AVF) flow rates during surveillance. Significant flow rate changes should prompt further investigation or treatment to avoid a failing fistula. Hemodialysis is known to alter the hemorrheologic and physiologic factors with a potential impact on measured flow rates. The aim of this study was to determine the difference in flow rate measured with duplex ultrasound before and after a single hemodialysis session in patients with brachial-cephalic fistulae.
  
  
  METHODS
  Patients with brachial-cephalic AVFs in our dialysis populations who were undergoing regular hemodialysis without recent intervention (less than six weeks) were invited to participate. Flow measurements were made pre-and post-hemodialysis using a Zonare ultrasound machine. The vascular scientist was always blinded to the pre-hemodialysis flow.
  
  
  RESULTS
  A total of 157 patients were identified with brachial-cephalic fistulae. Following exclusions, 119 patients were eligible. However, a further 58 were excluded because they declined or did not attend leaving 61 patients in the study. Paired t test showed a statistically significant reduction in flow rate of 105 mL/min (P=0.026) post-hemodialysis which equates to a -6.9% change in flow (95% C.I. -12.7 to -0.8%). Bland-Altman analysis showed limits of flow rate agreement between -599 mL/min and +810 mL/min (+/-1.96 s.d.).
  
  
  CONCLUSIONS
  Whilst we have shown a statistically significant change in flow rate post-hemodialysis, this is small and should be taken in the context of previously accepted interobserver variability. Therefore, the practical and financial considerations of implementing an AVF surveillance programme are likely to outweigh the minimal benefit of consistency that would be enabled by strict protocol of pre-hemodialysis flow measurements.
authors: Vascular Laboratory, Kings College Hospital, London - UK.
authors: Shakila
authors: S
authors: Chowdhury
authors: David
authors: D
authors: Goss
authors: Hiren
authors: H
authors: Mistry
authors: Matthew A
authors: MA
authors: Stephenson
authors: Paul
authors: P
authors: Seed
authors: Colin
authors: C
authors: Deane
authors: Domenico
authors: D
authors: Valenti
mesh_terms: D001166:Arteriovenous Shunt, Surgical; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015588:Observer Variation; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D006435:Renal Dialysis; D015203:Reproducibility of Results; D013997:Time Factors; D016896:Treatment Outcome; D018616:Ultrasonography, Doppler, Duplex; D034941:Upper Extremity / Q000098:blood supply*