Vascular Access for Hemodialysis - How to Maintain in Clinical Practice

Abstract

The physiologic effects of AV fistulas can be separated into local haemodynamic effects and systemic cardiovascular effects [7]. • Local haemodynamic effects: The effect of creating a fistula on the proximal artery is similar to making a hole in a dike. Flow in the proximal artery increases markedly in response to the sudden decrease in outflow pressure afforded by the fistula, so with forearm AV fistulas, brachial artery flow may increase 5 to 10 folds [8]. In the distal artery, the situation is not so simple. With small fistula, distal artery flow is maintained antegrade, away from the heart. With increasing fistula size, however, distal artery flow decreases until it reaches a standstill when the anastomotic length is equal to the proximal artery diameter. At this point, circus motion develops with antegrade flow during systole and retrograde flow during diastole through the fistula into the venous limbs. When the anastomotic length of the fistula communication increases, above the diameter of the proximal artery, reversed flow in the distal artery increases until it exceeds the antegrade flow [9]. • Systemic haemodynamic effects: The immediate effect of opening a fistula is to divert blood flow away from the rest of the peripheral circulation and into a special low-resistance path directly connecting the left side to the right side of the heart. Cardiac output increases acutely via increased rate and stroke volume. Arterial pressure falls, and heart rate increases; these changes are minimal with lowflow fistulas and increase with increasing fistula flow. Cardiac work also increases [10]. 4. Preoperative evaluation 4.1. Patient preparation for permanent hemodialysis access (modified from NKF, 2006 [ 11 ]) Good planning allows initiation of dialysis at the proper time with a permanent functioning access in place ready at the start of dialysis. • Patients with a glomerular filtration rate (GFR) less than 30 mL/min/1.73 m 2 and chronic kidney disease (CKD) stage 4 should be educated about all modalities of kidney replacement therapy (KRT) options, including transplantation, so that timely referral can be made for the appropriate modality and placement of a permanent dialysis access, if necessary.