Effects of heparin coating on the expression of CD11b, CD11c and CD62L by leucocytes in extracorporeal circulation in vitro.

Leucocyte adhesion molecules are involved in the leucocyte-endothelial interaction and in the activation of coagulation and binding of complement and endotoxin. Thus, they are important in inflammation, systemic acute phase reaction, ischaemia reperfusion injury and resistance against infections. The expression of the adhesion molecules CD11b, CD11c and CD62L on leucocytes and changes in plasma products of neutrophil activation (myeloperoxidase, lactoferrin) and complement activation (C3bc, SC5b-9 (TCC)) were examined in an extracorporeal circulation (ECC) model and the effects of Carmeda bioactive surface (CBAS) heparin coating (n = 7) of the circuits were compared to uncoated control circuits (n = 5). In this model, new 'unactivated' cells mobilized from the bone marrow could not interfere with descriptive measures of cell activation as seen in in vivo studies. In the control group, CD11b and CD11c were upregulated on monocytes and granulocytes during ECC, whereas CD62L was downregulated. Heparin coating reduced the increase in CD11b and CD11c on granulocytes (p < 0.02 at 2 h), but the delayed increase in CD11c on monocytes and the delayed downregulation of CD62L on granulocytes and monocytes did not reach statistical significance. Further, heparin coating also reduced the initial decrease in the absolute cell counts of monocytes and granulocytes (p = 0.01 at 2 h), reflecting reduced adhesion to the oxygenator/tubing. The increases in plasma myeloperoxidase, lactoferrin, C3bc and TCC were lower in the heparin-coated group compared to the control group. The increases in plasma myeloperoxidase and lactoferrin correlated significantly to the increase in CD11b (r = 0.71, p = 0.02 and r = 0.64, p = 0.05, respectively) and CD11c (r = 0.72, p = 0.008 and r = 0.72, p = 0.008, respectively) on granulocytes, suggesting interacting regulatory pathways in the process of neutrophil adhesion, activation and degranulation. Thus, in this in vitro ECC model, heparin coating of oxygenator/tubing sets reduced leucocyte activation and leucocyte adhesion-related phenomena.

Differences in blood activation related to roller/centrifugal pumps and heparin-coated/uncoated surfaces in a cardiopulmonary bypass model circuit.

An in vitro model cardiopulmonary bypass (CPB) circuit consisting ot tubing, oxygenator and venous reservoirs with either a roller or a centrifugal pump, and with either heparin-coated (Carmeda Bioactive Surface, CBAS) or uncoated surfaces, was studied with respect to 'blood activation', using small-scale-based blood volume (450 + 500 ml). Sixteen circuits were tested in each pump group, eight with and eight without heparin-coated surfaces, by circulating heparinized fresh human blood for 72 hours at 30 degrees C. Blood plasma, sampled at defined intervals, was analysed for haemolysis (lactate dehydrogenase and potassium), complement activation (C3bc and C5b-9 (TCC)), complement lytic inhibitors (vitronectin and clusterin), coagulation activation (fibrinopeptide A), granulocyte (lactoferrin and myeloperoxidase) and platelet (beta-thromboglobulin) activation and contaminating endotoxin. The heparin coating significantly reduced the concentrations of C3bc, TCC, fibrinopeptide A, lactoferrin, myeloperoxidase and beta-thromboglobulin. The two pump types did not differ with respect to these parameters, but the roller pump caused significantly higher increases in plasma LDH and potassium and significantly greater reductions in clusterin and vitronectin than the centrifugal pump. Endotoxin concentration was low at the start and after 24 hours in all groups. These results confirm that heparin-coated CPB surfaces reduce blood activation, and suggest that centrifugal pumps cause less haemolysis and less reduction in lytic complement inhibitors than roller pumps.

Roller and centrifugal pumps compared in vitro with regard to haemolysis, granulocyte and complement activation.

A Biomedicus centrifugal pump and a Polystan roller pump were compared in vitro with regard to differences in haemolysis, granulocyte and complement activation. Six circuits of tubing and oxygenators were connected to each pump. Heparinized fresh human blood was circulated for 72 hours in the systems. Blood samples were drawn at defined intervals. Haemolysis was assessed by determination of lactate dehydrogenase (LD) and potassium, and granulocyte activation by quantification of the granulocyte proteins calprotectin, lactoferrin and myeloperoxidase. Complement activation was assessed by measuring C3 activation products (C3b, iC3b and C3c), and the terminal C5b-9 complement complex (TCC). The results indicate more haemolysis and complement activation in the roller pump group, revealed by significantly higher concentrations of LD, potassium, C3 activation products and TCC. Calprotectin, lactoferrin and myeloperoxidase were all significantly increased in both groups, but the rise appeared earlier in the roller pump group. The concentrations of LD and potassium both correlated significantly with C3 activation products, indicating that complement activation may at least partly be responsible for the haemolysis.