Two years clinical experience with continuous arteriovenous hemofiltration in acute renal failure.

Clotting of hemofilters is the most frequent single cause of filter failure. These filters frequently clot in spite of acceptable hemodynamic and anticoagulation parameters. Sixty percent of filters which eventually clotted never filtered above 200 ml/hr. In our experience maximum ultrafiltration rates of 500 ml/hr to over 1000 ml/hr are rarely achieved in routine clinical usage. Finally, a disproportionate number of filters accessed to the lower leg either clotted or were discontinued for subsequent dialysis. Thus, we conclude that lower leg accesses should be avoided if possible. Further, to prevent clotting, in addition to maintaining adequate anticoagulation and cardiac output, maximum ultrafiltration rates should be sought. To achieve maximum ultrafiltration rates, a good vascular access is primary. Also, a vacuum system may be needed and perhaps routinely used to obtain filtration rates near 500 ml/hr. These high filtration rates will also reduce the need for hemodialysis, the second most common reason for filter discontinuation.