Fibrin deposition in disposable dialyzers before and after re-use

We have estimated the degree of fibrin deposition as well as changes in dialyzer efficiency of Gambro Optima 13.5 mu dialyzers, re-used up to six times in six regular dialysis patients. After each dialysis the dialyzer was rinsed and left filled with formaldehyde. The patients were given I-125-fibrinogen before the study. The radioactivity from the dialyzer was continuously measured during each dialysis and rinsing procedure. Urea and creatinine clearances were determined 30 min after start of each dialysis. After the last re-use the dialyzer membranes were removed and divided into sections and the radioactivity of each section was measured. Twice as much fibrin deposition was found near the blood inlet of the dialyzer as near the outlet. A higher fibrin deposition was found after each re-use than after the initial dialysis. The clearances of urea and creatinine were scarcely influenced by the re-use. The half-life of fibrinogen in the patients was in the same range as in normal subjects.