Uncontrolled reoxygenation by initiating cardiopulmonary bypass is associated with higher protein S100 in cyanotic versus acyanotic patients

Background: The systemic reoxygenation injury produced by initiating cardio pulmonary bypass (CPB) in infants with cyanotic heart disease may be associ ated with cerebral dysfunction and injury. Increased protein S100 (S100) se rum levels may indicate cerebral and blood brain barrier damage as well as inflammatory changes, therefore serving to quantify these changes. The pres ent clinical study assessed S100 in cyanotic patients undergoing CPB with n ormoxic versus hyperoxic paO(2) in acyanotic cases and in controls without CPB. Methods: 43 patients with congenital heart disease aged 5 days to 15 y ears (mean 4.4 years) were enrolled consecutively and divided in four group s: (1) Cyanotic infants undergoing controlled normoxic reoxygenation on CPB (n = 12), (2) cyanotic infants undergoing uncontrolled hyperoxic reoxygena tion on CPB (n = 9), (3) acyanotic infants operated with CPB (n = 16)and (4 ) patients operated without CPB (n = 6). Blood samples were collected after induction of anesthesia (A), up to 4 hours after surgery (B) and at postop erative day one (C). Results: Preoperative S100 serum levels [mug/l] in all groups were below clinical relevance. S100 increased markedly after surger y in groups 1 and 2. Differences in postoperative S100 levels were signific ant between groups 1 (0.45 +/- 0.13) and 3 (0.35 +/- 0.09; p = 0.018), betw een groups 2 (1.41 +/- 0.47) and 3 (p = 0.01), and between groups 2 and 4 ( 0.29 +/- 0.09; p = 0.045). There were no significant differences in postope rative S100 levels (B) between groups 1 and 2 (p = 0.05), groups 1 and 4 (p = 0.05), or groups 3 and 4 (p = 0.93). Conclusion: Uncontrolled hyperoxic reoxygenation on CPB for surgical correction of congenital heart defects is associated with higher S100 levels in cyanotic infants as compared to acya notic patients undergoing comparable operations.