There were in vitro and prospective, observation cohort components to this a priori planned substudy evaluating bedside allogeneic erythrocyte washing, with a cell saver, during cardiac surgery. Laboratory data were collected from the first 75 washed units given to a subset of patients nested in the intervention arm of a parent clinical trial. Paired pre- and postwash samples from the blood unit bags were centrifuged. The supernatant was aspirated and frozen at –70°C, then batch-tested for cell-derived microvesicles, soluble CD40 ligand, chemokine ligand 5, and neutral lipids (all previously associated with transfusion reactions) and cell-free hemoglobin (possibly increased by washing). From the entire cohort randomized to the intervention arm of the trial, bedside washing was defined as feasible if at least 75% of prescribed units were washed per protocol.
Paired data were available for 74 units. Washing reduced soluble CD40 ligand (median [interquartile range]; from 143 [1 to 338] ng/ml to zero), chemokine ligand 5 (from 1,314 [715 to 2,551] to 305 [179 to 488] ng/ml), and microvesicle numbers (from 6.90 [4.10 to 20.0] to 0.83 [0.33 to 2.80] × 106), while cell-free hemoglobin concentration increased from 72.6 (53.6 to 171.6) mg/dl to 210.5 (126.6 to 479.6) mg/dl (P < 0.0001 for each). There was no effect on neutral lipids. Bedside washing was determined as feasible for 80 of 81 patients (99%); overall, 293 of 314 (93%) units were washed per protocol.
Bedside erythrocyte washing was clinically feasible and greatly reduced concentrations of soluble factors thought to be associated with transfusion-related adverse reactions, increasing concentrations of cell-free hemoglobin while maintaining acceptable (less than 0.8%) hemolysis.
- Allogeneic erythrocyte transfusions occur frequently in cardiac surgical patients.
- Allergic and febrile reactions and transfusion-associated circulatory volume overload can occur in the setting of allogeneic erythrocyte transfusion.
- Cytokines, chemokines, and cell-derived particles (biologic response modifiers) in the supernatant of allogeneic erythrocytes may cause a proinflammatory response of the recipient’s immune system.
- Feasibility of bedside allogeneic erythrocyte washing and the differences in biologic response modifiers pre- to posterythrocyte washing are not established.
- This study found that bedside point-of-care washing of allogeneic erythrocytes was feasible for 99% of elective cardiac surgical patients included in the study, with 93% of allogeneic erythrocyte units washed per study protocol.
- Biologic response modifiers were significantly decreased in supernatant after allogeneic bedside erythrocyte washing when compared with before washing.
- Cell-free hemoglobin was significantly increased after allogeneic erythrocyte washing when compared to before washing. Percent hemolysis was assessed in a five-unit subset of washed erythrocyte units and was less than 0.8%.
- Future reporting of the larger randomized control trial results will help to determine impact of these findings on clinical outcomes after cardiac surgery.
- Cell-free hemoglobin and percent hemolysis in washed cells should be further assessed in relation to clinical outcomes and findings should be validated in other cardiac surgical cohorts.