Hemofiltration and thrombus formation in hollow fiber hemodialyzers.

Abstract

The effect of proximal hemofiltration on thrombus formation in hollow fiber dialyzers was investigated in a controlled study of 9 patients. Both Dacron wool adsorption filters and polyurethane foam microporous filters were evaluated.Patients were dialyzed alternately on control (no filter) and treatment (with filter) regimens, each period consisting of 3–6 dialyses, with a minimum of 14 dialyses in total for any patient. Length of dialysis, blood flow rate and heparin administration were kept constant for each patient throughout the study. The degree of thrombus formation in the dialyzers was estimated from pre- and post-dialysis dialyzer saline rinse volumes and expressed as fiber bundle volume loss (FBVL).Four patients (control FBVL ≤ 10%) showed a significant (p < 0.05) decrease in FBVL when a filter was incorporated in the dialyzer circuit. In the remaining 5 patients (control FBVL < 10%) there was no significant change in FBVL when using a filter. Both filter types produced similar results. Use of filters produced no adverse effect on platelet count, hemoglobin level or levels of fibrinogen and fibrinogen degration products.Examination of filters after dialysis, by scanning electron microscopy showed that they acted as adsorption filters. No cellular aggregates were found in any filter. There was no correlation between FBVL and the amount of cellular elements adsorbed by the filter.In summary, hemofiltration produced a significant reduction in FBVL and hence, blood loss, in the patients with greatest need, i.e. those with control FBVLs ≤ 10%. In addition, the results suggest that the most important factor in determining a patient's potential for thrombus formation may be the interaction between blood proteins and the membrane surface.