Detection of hemodialysis access outlet stenosis by measuring outlet resistance

Stenosis of the outflow segment of hemodialysis access grafts frequently leads to thrombosis and loss of the access. Previous studies have shown that early detection and correction of the stenosis can prevent graft failure. The purpose of the present study was to compare four methods of detecting outflow segment stenosis: measurement of the pressure in the venous line during dialysis, measurement of the pressure in the distal portion of the access graft, measurement of the relative resistance of the outflow segment of the graft relative to the total resistance of the graft, and measurement of recirculation of venous dialysis blood into the dialysis arterial line. The graft pressure was determined by measuring the pressure in the dialysis venous line with the blood pump turned off. The relative resistance of the outflow segment was determined by dividing the graft blood flow-induced pressure decrease across this segment by the difference between mean systemic arterial and venous pressures. Sixty-eight chronic hemodialysis patients were followed prospectively for 11 months. Sixty-nine complications occurred in 31 accesses in 24 patients. Outlet obstruction was present in 21 of the 31 accesses. Relative graft resistance and recirculation rate measurement were found to be most useful in detecting hemodialysis access outlet obstruction.