Platelet Loss across the Hemofilter during Continuous Hemofiltration

Abstract

Background Thrombocytopenia is a common finding in patients in the intensive care unit receiving continuous renal replacement therapy (CRRT). It is unknown if the hemofilter itself contributes to the platelet loss. Objective To measure the direct effect of the hemofilter on platelet counts during CRRT. Design Prospective, observational study Setting Intensive care unit of a University hospital Patients Critically ill patients with acute renal failure receiving CRRT. Methods Two samples of blood were drawn simultaneously, pre-filter and post-filter, and analyzed for platelet count. A correction factor was applied to the post-filter platelet count to adjust for the hemoconcentrating effect of net ultrafiltration. Results Forty-eight sets of paired data from 22 patients were studied. There was a small but significant decrease in mean platelet count across the hemofilter. The mean platelet count drop was 2.32 ×109/L (s.e. 1.06, p=0.0487, 95% CI (0.01,4.62)). Blood flow was strongly related to degree of platelet loss, with a decreased loss of 0.07 ×109/L for every ml/min increase in blood flow (p=0.015). There was no overall decrease in concurrently measured red cell counts across the hemofilter. However, there was a machine-specific affect on red cell loss (p<0.0001). The total calculated daily platelet loss across the filter was 625 ×109 cells. Conclusion The hemofilter may contribute to the thrombocytopenia seen during CRRT, by means of either destruction or retention of platelets during passage. This affect appears attenuated by higher blood flows. This information is useful in the assessment of a low platelet count in patients receiving CRRT.

Cellulose Triacetate Dialyzer Reduces Platelet Loss during Continuous Veno-Venous Hemofiltration

“…Recently, Mulder et al [3] have reported that hemofiltration itself is one of the important reasons in thrombocytopenia during CVVH. However, there are no reports on whether differ- ent hemofilters affect platelet counts differently during CVVH.…”

“…However, the hemofilter itself plays an important role in the genesis of thrombocytopenia as a result of immediate destruction or retention of platelets as they pass through the filter [3] . Thrombogenicity of a dialysis membrane depends on the composition of the membrane as well as on the area and geometry of the dialyzer.…”

The incidence of thrombocytopenia associated with continuous renal replacement therapy in critically ill patients

“…The authors estimated a total daily platelet loss of 625 Â 10 9 cells, displaying the demand placed on platelet production to maintain counts. 12 The filter type has also been implicated in platelet loss, suggesting a more substantial decline depending on hemofilter type. Liu et al compared platelet loss across a polysulfone and cellulose triacetate filters with or without anticoagulation.…”

“…While the literature is minimal, this data signifies not only the presence of a reduction in platelets in patients on CRRT, but the relation of specific CRRT attributes to the risk and degree of platelet loss. 1,10,12 Missing from this literature is the pathology in which thrombocytopenia develops. Oever et al suggested a trapping phenomenon in the extracorporeal circuit resulting in activation of the platelets and sequestration.…”

“…Unlike past data there was no correlation identified between circuit anticoagulation or circuit flow rate and the rate of thrombocytopenia. 10,12 We did however evaluate the impact of this platelet decline on the care of patients. Patients experiencing a decline in platelets had a substantially greater rate of being tested and treated for HIT, as well as holding anticoagulation.…”