Severe Clotting During Extracorporeal Dialysis Procedures

The prevention of extracorporeal clotting during hemodialysis maximizes the effectiveness of treatment by maintaining patency in the dialyzer blood compartment and thereby obviating several important consequences. For example, clotting leads directly to blood loss, as much as 200-300 ml for each episode, depending on the total volume of the extracorporeal circuit. In addition, clotting reduces dialyzer clearance and thus the adequacy of dialysis treatment. Finally, clotting increases the overall cost and complications of hemodialysis. Prevention of clotting during extracorporeal dialysis procedures is accomplished successfully in most instances using intermittent systemic heparinization and hemodialysis sometimes can be accomplished without anticoagulation at all (1, 2). However, occasional patients manifest extreme resistance to heparin and suffer vascular access thrombosis or recurrent severe clotting of the extracorporeal circuit. Although the latter phenomenon, severe clotting of the extracorporeal circuit, is observed infrequently (3, 4), it is striking and problematic when it occurs. In evaluating possible causes and appropriate treatments for such clotting, several important factors which must be considered include: the characteristics of the extracorporeal circuit and its components, intrinsic abnormalities in circulating coagulation factors, and the effects of exogenous agents on the coagulation system.