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Complement activation and excessive bleeding in cardiopulmonary bypass surgery


Complement activation has been associated with postoperative bleeding. We investigated the association between complement activation, coagulation and fibrinolysis systems, and postoperative excessive bleeding in cardiopulmonary bypass (CPB) surgery.


We performed a nested case–control study of 50 patients undergoing CPB, 27 (54%) men and 23 (46) women, mean age 66.5 (SD 9.6) years. Excessive bleeding (EB) was defined as blood loss higher than 1 l over the 24 hours. Demographic variables, comorbid conditions, surgical procedures and postoperative variables were collected. We recorded data related to coagulation, fibrinolysis, complement, and blood loss at different time points, preoperative, at ICU admission (0 hours) and 4 and 24 hours after surgery. We used the Pearson chi-squared test, the Fisher exact test, the Student t test and the Mann–Whitney U test for nonparametric variables and Spearman's rho for nonparametric correlations.


EB patients had higher activation of classical, alternative and final pathways of complement at 0 and 4 hours. Also we found a significantly higher decreasing of several components of complement from preoperative values to postoperative values (0 and 4 hours) associated with EB. This decrease of complement was correlated with a similar decrease of platelets and antithrombin levels between the preoperative period and 0 hours, and an increase of D-dimer levels in the first 4 hours.


Complement activation was associated with EB due, in part, to a greater activation of platelets, coagulation and fibrinolysis.

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Iribarren, J., Jimenez, J., Brouard, M. et al. Complement activation and excessive bleeding in cardiopulmonary bypass surgery. Crit Care 11 (Suppl 2), P256 (2007).

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