Venturi grafts for hemodialysis access

Vascular access grafts can produce venous and puncture site stenosis, and excessive shunted flow. A vascular access graft that controls the shunted flow at 500-650 ml/min by venturi flow resistance, and offers the potential for reduced venous stenosis, is presented. Twelve venturi grafts consisting of 6 mm ePTFE, with a thermally formed venturi resistance, were implanted in a canine femoral arterio-venous (A-V) model and cannulated for simulated dialysis for periods up to 6 months. Pressures, bleeding times, and puncture site healing were compared at sites upstream and downstream of the venturi. Nine 6 mm ePTFE grafts were implanted as controls. Venturi and control graft patency rates were similar: 90% for venturi grafts and 89% for control implants at 4 months. Measurements verified pressure dissipation by the venturi from 85 to 15 mmHg, delivering near-normal pressures to the vein; downstream pressures were 22 mmHg higher in controls. Sites downstream of the venturi did not bleed at 4 min, whereas bleeding was often noted after 9 min at other sites. Puncture sites upstream of the venturi had less stenosis and less mural thrombus than sites downstream of the venturi, and compared favorably with puncture sites in the control grafts. This improved healing and low pressure delivery to the vein may offer clinical advantages.