Blood flow and thrombosis in arteriovenous fistulae.

An increasing number of patients are being maintained on long-term haemodialysis for end-stage renal failure, despite the renal transplantation programme and the introduction of peritoneal dialysis. Until prevention or cure of chronic renal failure becomes a possibility patients will continue to require long- lasting vascular access via surgically created arteriovenous fistulae. The Brescia-Cimino radiocephalic fistula at the wrist has remained the best procedure, and many patients use one satisfactorily for several years; even if later complications occur such as thrombosis or stenosis, the fistula can often be salvaged for further long-term use. In a group of patients, however, recurrent thrombotic problems occur, which can be life-threatening if access proves impossible. This study was aimed at identifying risk factors for thrombosis in these patients, and to improving clinical management of fistula complications. Initially the size of the problem was assessed by studying over 150 patients admitted to the dialysis programme over five years, from which two main facts emerged. (1) Analysis of management showed that more fistulae could be salvaged than was previously thought. (2) Although more problems occurred in patients with small vessels, it was impossible to predict which fistulae would fail. A prospective study of blood flow through the fistula at the time of operation showed that thrombosis occurred equally often in high and low flow fistulae, and fistulae with low initial flow could develop adequately for dialysis. This suggested that technical factors alone could not explain failure of fistulae. Patients maintained on dialysis with and without thrombotic problems were then studied, and significant differences in parameters of rheological and platelet function emerged. A prospective study was made of a group of patients undergoing fistula construction, who had blood taken pre-operatively for estimation of rheological and haemostatic factors, including platelet function. The later incidence of thrombosis after one year of follow-up was related to the pre-operative tests. It was possible on the basis of these tests to separate the thrombotic from the non-thrombotic patients, which has important implications for prophylaxis.