Retransfusion of a patient's shed blood during cardiopulmonary bypass is attractive since it reduces the need for allogeneic transfusion, minimizes cost, and decreases transfusion related morbidity. Heterologous transfusions are linked to increased long term mortality after cardiac surgery. However, brain damage after cardiac surgery with retransfusion of shed blood is a significant cause of morbidity, including post-operative, short-term and long-term cognitive dysfunction, and mortality. Among the preoperative and postoperative factors that have a significant correlation with stroke are diabetes, hypertension, and recent myocardial infarction. It is well-documented that these factors are more prevalent in minorities. Evidence suggests that lipid microembolisms associated with the retransfusion of the shed blood are the predominant causes of the neurocognitive disorders. Traditional techniques to remove the lipids from the shed blood include screens and centrifugation by cell processors, both of which are decades old technologies with significant drawbacks. Filters clog, are inefficient, and suffer from throughput constraints. Centrifugation is also not efficient at removal of the lipids, removes beneficial bloo components such as platelets and clotting factors, and circulates only the concentrated red blood cells (RBCs) to the patient. Centrifugation is also time-consuming, can cause fragmentation of RBCs, and may lead to activation of clotting and other inflammatory cascades. A new technology is needed that is more efficient at removal of the lipids, concentrates the RBCs without hemolysis, and operates continuously. FloDesign Sonics is developing a novel acoustophoretic filtration system with the potential to deliver these desired characteristics. Unlike other acoustophoretic separation systems, the novel ultrasound technology works at the macroscale, and is therefore able to process larger flow rates than typical microelectromechanical (MEMS) scale acoustophoretic separation devices. Results from a first prototype study indicate successful separation of RBCs and lipid particles. The technology has the potential to remove nearly all of the lipids, provide healthy RBCs, and operate continuously at a substantially reduced device cost. [Our proposed device would replace the cell saver in all cardiac surgical cases to preserve the whole blood elements while removing the dangerous particulate matter and lipid particles that accumulate within the chest cavity during heart surgery with little to no dilution of blood volume. Our device has the additional cost benefit that it woul not require a dedicated technician to run the device.] FloDesign Sonics Inc., Dr. Rust and Dr. Kennedy from Western New England University, Dr. Engelman, MD, Cardiac Surgeon at Bay State Medical Center in Springfield, Massachusetts, and Dr. Zwicker, MD, Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, propose to design and test an acoustophoretic system for removal of micro-lipids from a blood stream with a flow rate of 2 L/hr, lipid removal in excess of 80%, and recovery and concentration of 80% of RBCs. Phase II focuses on system optimization, biocompatibility, and testing of the acoustophoretic device in a perioperative setting with an animal model. Measurements of relevant physiological parameters such as cerebral embolization post-surgery are performed to quantify the improved surgical outcomes provided by the novel system.
Retransfusion of a patient's shed blood during cardiopulmonary bypass surgery is preferred over allogeneic blood transfusion, but lipid micro-emboli in the shed mediastinal blood lead to increased risk of stroke, cognitive dysfunction, and mortality. Current reinfusion technology, i.e., centrifugation, is only partly effective at lipid removal, [and does not preserve the other blood elements, specifically the plasma within the shed blood.] Acoustophoretic separation has the potential to significantly enhance lipid removal, operate continuously, [and to preserve the whole blood elements while removing the dangerous particulate matter and lipid particles at a substantially reduced cost.