CHANGES IN NEUTROPHIL CD11B/CD18 AND L-SELECTIN EXPRESSION AND RELEASE OF INTERLEUKIN-8 AND ELASTASE IN PEDIATRIC CARDIOPULMONARY BYPASS

Children undergoing cardiopulmonary bypass (CPB) surgery for congenital heart defects develop an acute post-operative capillary leak which may be due to endothelial injury inflicted by adherent neutrophils (PMN). Direct immunofluorescence and flow cytometry were used to measure CD11a/CD18, CD11b/CD18 and L-selectin (L-S) expression on circulating PMN in CPB circuits containing human blood and in children undergoing CPB. In vitro, a general rise in CD11b/CD18 expression over 2 h contrasted with complete loss Of L-s in a small but progressively increasing proportion of PMN. Marked but inconsistent changes in CD11b/CD18 and L-S were observed in vivo, in conjunction with fluctuations in circulating PMN count. Circulating IL-8 was detected starting at rewarming from hypothermia and reperfusion of the heart and lungs with a simultaneous, closely correlated rise in both PMN count and circulating elastase. IL-1 and TNF were not detected. These studies demonstrate changes in the pathways of PMN-endothelial interaction during and after CPB.