May RE, Ikizler TA, Schulman M, Schulman G, Yenicesu M,
Himmelfarb J, Hakim RM
Predictive measures of vascular access thrombosis
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1413 1996
In ninety patients at monthly intervals venous pressure was measured at
preset dialyzer blood flow rates (Qb) of 200, 300, and 400 ml/min and
access recirculation was measured using the classic urea dilution, slow
flow method. A baseline access flow measurement was made by ultrasound
velocity dilution in all patients and Doppler studies were performed in 60
of the patients. Stenosis identified by Doppler ultrasound was associated
with significantly lower access blood flow. Venous pressure and
recirculation had no predictive value but the access blood flow, especially
when less than 765 ml/min, was highly predictive of thrombosis.
Comment: The correlation between access blood flow and access
survival found in this study is similar to findings by Besarab and by Sands
using Doppler flow, by Boereboom using ultrasound dilution, and by Depner
using ultrasound dilution (see abstract page 1405). The cutoff value of
700-800 ml/min is probably not a fundamental flow below which access
devices do not survive but rather an indicator of progressive intimal
hyperplasia that will eventually cause the access to fail unless treated
with angioplasty or surgical revision. Fistulas have been known to survive
for prolonged periods of time with low flow rates, so the rate of change in
flow is probably also a factor to consider when deciding upon angiography.
The failure of venous pressure to predict failure is contrary to findings
by Schwab and others. The insensitivity of access recirculation
measurements as a predictor of failure is consistent with clinical
experience.
(Thomas A. Depner, M.D., University of California at Davis)
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Am Soc Nephrol
Basic hemodialysis :
Vascular Access: graft/fistula