COMPLEMENT ACTIVATION DURING CARDIOPULMONARY BYPASS IN INFANTS AND CHILDREN - RELATION TO POSTOPERATIVE MULTIPLE SYSTEM ORGAN FAILURE

Twenty-nine children 3 months to 17 years of age undergoing operations for congenital heart disease were included in this prospective study. Complement activation, activation of the plasma contact System, leuko cytes, leukocyte elastase release, and C-reactive protein were studied during and after cardiopulmonary bypass for the first postoperative w eek and related to multiple system organ failure occurring in eight (2 7.5 %) of the 29 children. During cardiopulmonary bypass complement ac tivation via the alternative pathway as indicated by significant conve rsion of C3 (expressed by C3d/C3) and abnormally high C5a values at th e end of cardiopulmonary bypass without consumption of C4 was shown in all children. At the end of cardiopulmonary bypass, C3 conversion was significantly higher in the eight patients with multiple system organ failure than in the others (p < 0.05), whereas no difference in C5a l evel was shown. All children had a significant increase in leukocyte c ount directly after protamine administration (p < 0.0001) and elastase release during cardiopulmonary bypass that was significantly higher i n patients with multiple system organ failure than in those without (p < 0.05), Consumption of prekallikrein as an indicator of activation o f the Hageman system was not detectable during cardiopulmonary bypass in any child. After cardiopulmonary bypass, in patients without multip le system organ failure, C3d/C3 decreased and reached preoperative val ues within the first postoperative week, whereas, in patients with mul tiple system organ failure, C3d/C3 increased further, reaching a maxim al value on the third postoperative day. In comparison with patients w ithout multiple system organ failure, patients with multiple system or gan failure showed a severe decrease of C4 (with minimal values on the third postoperative day), suggesting consumption by activation of the classic pathway of the complement system or a hepatic synthesis defic iency. Prekallikrein values were also significantly lower in patients with multiple system organ failure than in the others, with a maximal difference on the third postoperative day (p < 0.005). C-reactive prot ein was significantly lower in patients with multiple system organ fai lure than in the others for the first 2 postoperative days (p < 0.05), probably because of severe hepatic failure in patients with multiple system organ failure. This study demonstrates that, in children, cardi opulmonary bypass induces complement activation principally via the al ternative pathway. It suggests a relationship between complement activ ation and multiple system organ failure observed in the postoperative period. Furthermore, it points out the role of multiple system organ f ailure itself on the C3 conversion and on the synthesis of the markers of the inflammatory response in children after heart operations.