Haemodynamics of Brachial Arteriovenous Fistula Development

Abstract

This study observes the development of brachial arteriovenous fistulae, and assesses methods of predicting potential usefulness for haemodialysis. Creation of an adequate brachial fistula causes significant changes in blood flow to the forearm and hand. A prospective study of fifteen consecutive patients undergoing brachial arteriovenous fistula formation for haemodialysis was undertaken. Clinical measurements and coloured flow Doppler measurements were performed pre operatively, immediately post operatively and at two and eight weeks after surgery. The morphology of the fistula was studied and the volume flow was measured. Digital pressure was measured pre and post exercise at each visit. Fourteen fistulae worked well by eight weeks. There was an immediate large increase in brachial artery blood flow and by two weeks all fistulae that went on to develop well had a brachial artery flow of more than 700 mls/minute. The cephalic vein mean diameter pre operatively was 2.39 mm and increased to 5.4 mm by two weeks post operatively. Fistulae with flows over 400 mls/minute at two weeks had a good outcome. There were significant differences in digital pressure after fistula formation (P (2) 0.05). Digital mean arterial pressure dropped from 118 mm Hg pre-operatively to 98 mm Hg post operatively, at rest, and 89 mm Hg after exercise. Four patients developed forearm/hand claudication on exercise or signs of distal ischaemia. Three of these were diabetic with calcified vessels. All patients with a suitable cephalic vein should have attempted fistula formation rather than recourse to use of a synthetic graft. In diabetics creating a shunt in an already marginally competent vascular tree exposes the pa-tient to risk of significant hand ischaemia.