Blood cell rheologic deterioration by complement activation during experimental prolonged perfusion with membrane oxygenation

In order to understand the microcirculatory disturbances during clinical ECMO, the relation of complement activation to blood cell rheologic parameters during prolonged perfusion with membrane oxygenation was studied in 10 experiments using fresh human donor blood. The perfusion set-up was a standard ECMO circuit without a patient. Blood rheologic parameters reflecting the fluidity of blood in the microcirculation were analysed by a St George's Filtrometer. Changes in complement fractions C3a and C5a were measured by the radio-immunoassay (RIA) technique and the TCC (terminal complement complex) by ELISA technique. Samples for complement activation and blood rheological analysis were taken at 24 hours for correlation. There were strong and significant correlations between red and white cell rheologic parameters with all complement fractions. These observations indicate that complement activation plays a significant role in the deterioration of blood rheology during extracorporeal circulation. Improvements in biocompatibility and blood protection are required if this technology is to be made safer.

Cardiopulmonary bypass support for treatment of left ventricular failure following coronary artery bypass grafting: the effects on epicardial microflow and graft flow

The relationship between graft blood flow, epicardial microflow and mean arterial pressure were studied to evaluate the use of repeated cardiopulmonary bypass (CPB) support for intraoperative heart failure following aorto-coronary bypass surgery. Ten patients with unstable angina and suffering from intraoperative heart failure (group A) were compared to 22 patients with stable angina (group B). In group A, during heart failure, the mean arterial pressure fell by 41% (29.9 +/- 6.8 mmHg, p < 0.01), graft flow (GF) by 67% (9.2 +/- 2.6 ml/min, p < 0.01) and epicardial microflow by 64% (19 +/- 4 AU, p < 0.01). After 15-56 min of assisted CPB support, the epicardial microflow and GF were partially restored. There were significant correlations between GF, epicardial microflow and CPB time. In group B, after protamine infusion, the epicardial microflow and GF were significantly greater than group A values (66 +/- 14 AU, p < 0.001 and 29 +/- 9 ml/min, p < 0.001, respectively). It is concluded that the use of temporary assisted CPB support to treat intraoperative heart failure allows the recovery of the myocardium and thereby restores the mean arterial pressure. The recovery of GF and epicardial flow occurred to a lesser extent. CPB support appeared to be suitable for about 60 min, probably because of increasing disturbance to the GF and the epicardial microcirculation.

The effect of prolonged perfusion with a membrane oxygenator (PPMO) on white blood cells

Preserving the rheological properties of whole blood cells is vital for their smooth passage in the capillaries without causing blockage and disturbances in the microcirculation. To evaluate the effect of mechanical trauma on the rheology of white blood cells during prolonged perfusion with membrane oxygenation (PPMO), 16 in vitro experiments were conducted for 72 hours. The St George Carrimed Filtrometer was used to estimate the plasma white cell filtration rates (P-WFR). Also an in vitro estimation of the ability of individual cells to pass through capillaries, the white blood cell clogging rate (WBC-CR), the number of clogging particles (WBC-CP), the total white blood cell count (T-WBC) and two in vitro estimations to assess the effect of aggregates and stiff cells in blocking the microcirculation were performed. The traumatized white cells reduced their mean P-WFR by 37% +/- 9, 72% +/- 2 and 76% +/- 2 at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CR was increased to 15.2 +/- 1.5, 32.6 +/- 2.2 and 40.3 +/- 8.3 x 10(2)%/ml at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CP was increased to 6.6 +/- 1.5, 9.7 +/- 1.2 and 13.9 +/- 2.1 x 10(6)/ml at 24 hours (p < 0.05), 48 and 72 hours respectively (p < 0.001). The T-WBC was decreased to 55% +/- 0.3, 23% +/- 0.2 and 14% +/- 0.1 and 14% +/- 0.1 at 24, 48 and 72 hours respectively (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood cell rheological changes during prolonged perfusion with membrane oxygenation (PPMO) using perfluorochemicals

The aim of this study was to discover the effect of the perfluorochemical FC-43 on blood cell rheology during experimental prolonged perfusion with membrane oxygenation (PPMO). Using fresh human blood from healthy donors, six experiments with FC-43 in one clinical dose of 30ml/kg, another six with a dose of 1 0ml/kg, and 16 controls were pumped for 72 hours in a perfusion system containing an oxygenator similar to an extracorporeal membrane oxygenation circuit. Blood trauma was analysed using the St George's Filtrometer by estimating blood cell filtrability, clogging particles and clogging rate; the latter two reflecting blood cell aggregability. At 72 hours the filtrability of red cells was reduced by over 95% and 7.0% in the FC-43 groups and controls respectively; the FC-43 groups showed significantly (p < 0.01) greater reductions during perfusion. Both FC-43 concentrations increased the rheological damage to white cells from the outset. The white cells showed a greater tendency to clog than the red cells, suggesting an increased aggregability during prolonged perfusion. The 30ml/kg FC-43 dose induced relatively more damage than the doses in the other groups. This study suggests that FC-43 increased blood cell damage during PPMO in a dose-related manner, and that FC-43 during PPMO should preferably be made less toxic if it is to be used routinely as a blood substitute for prolonged extracorporeal circulation.