Red blood cell trauma during cardiopulmonary bypass: narrow pore filterability versus free haemoglobin

Ten patients admitted for coronary artery bypass grafting were investigated with respect to the influence of cardiopulmonary bypass (CPB) on red blood cell (RBC) trauma. Blood samples were collected prior to, at the start of, and at 30 and 60 min of CPB. RBC deformability was assessed by filtering r esuspended RBCs through a polycarbonate membrane using a computer-controlle d filtrometer. Muitiple regression analysis was employed to evaluate RBC fl ow-curve characteristics denoted by the initial filtration rate (IFR) and c logging slope (CS). Release of free haemoglobin was determined concomitantl y. IFR was estimated at 90.39 mu l/s and CS at -5.32 mu l/s(2) prior to CPB . During 60 min of CPB, neither IFR nor CS deviated significantly (p > 0.05 ) from these reference values. However, release of free haemoglobin increas ed significantly (p < 0.018) from the start: of CPB to the 60-min determina tion. In conclusion, 60 min of CPB seems not to alter significantly RBC def ormability in a 5 mu m pore filtration model, despite a significant release of haemoglobin.