Direct Detection of Red Blood Cell Fragments: A New Flow Cytometric Method to Evaluate Hemolysis in Blood Pumps

Pump induced hemolysis is presently evaluated by measuring plasma free hemoglobin (fHb). However, this method has disadvantages because quantification of fHb depends on hematocrit (HCT) and hemoglobin (Hb) levels. The aim of this work was to devise a hemoglobin independent method, capable of quantifying cell trauma directly by measuring the number of red blood cell (RBC) fragments. Whole blood flow cytometry was used to quantify circulating RBC fragments derived from a roller pump (Sarns, Inc. Model 2 M 6,002) and a centrifugal pump (Gyro C1E3, Kyocera Corp.). The pumps were tested in a mock circuit for 2 hr (5 L/min flow against 100 mm Hg pressure head). Red blood cell fragments were quantified by a phycoerythrin (PE) labeled glycophorin A antibody specific for erythrocytes. Red blood cell fragments were smaller than the intact RBC population and overlapped in size with the platelet population (based on forward- and side-light scattering measurements). For the roller pump, the values for RBC fragments increased from 1,090 ± 260/&mgr;l at 0 min to 14,880 ± 5,900/&mgr;l after 120 min. In contrast, using the centrifugal pump, there was little increase in RBC fragments (from 730 ± 270/&mgr;l at 0 min to 1,400 ± 840/&mgr;l after 120 min). Flow cytometry can be used for the rapid, sensitive, hemoglobin independent evaluation of pump induced RBC trauma.