Effect of mechanical ventilation during cardiopulmonary bypass on oxidative stress: a randomized clinical trial.

BACKGROUND: Cardiopulmonary bypass (CPB) causes systemic oxidative stress response and endothelial damage in systemic organs. We investigated the effects of positive end-expiratory pressure (PEEP) and mechanical ventilation (MV) applications on oxidative stress in CPB. METHODS: Seventy-one patients were recruited and 60 completed the study. Randomized groups: MV off (Group 1); MV on, tidal volume (TV) at 3-4 mL.kg-1 (Group 2); MV on, TV at 3-4 mL.kg-1, PEEP at 5 cmH2O (Group 3), n = 20 in each group. As oxidative stress markers, we used glutathione peroxidase (GPx), total antioxidant status (TAS), total oxidant status (TOS), total and native thiol (TT, NT), malondialdehyde (MDA), and catalase. We also investigated the correlation between oxidative stress and postoperative intubation time. RESULTS: The postoperative GPx levels in Group 2 were higher than Group 3 (p = 0.017). In groups 2 and 3, TAS levels were higher postoperatively than intraoperatively (p = 0.001, p = 0.019, respectively). In Group 2, the TT levels were higher postoperatively than preoperatively and intraoperatively (p = 0.008). In Group 3, the postoperative MDA levels were higher than preoperatively (p = 0.001) and were higher than both postoperative levels of Group 1 and 2 (p = 0.043, p = 0.003). As the preoperative TAS (Group 2) decreased and the postoperative NT (Group 2) and catalase (Group 3) increased, the postoperative intubation time lengthened. CONCLUSION: MV ( 3-4 mL.kg-1) alone seems to be the most advantageous strategy. Prolonged postoperative intubation time was associated with both increased NT and catalase levels.