Nitrotyrosine and its role in assessing the severity of oxidative stress and predicting the incidence of early postoperative complications

Background. Currently, the incidence of complications and perioperative mortality in cardiac surgery is still higher than in general surgery. This is partly associated with the development of oxidative stress, which is regarded as excessive accumulation of reactive oxygen species and nitrogen species. There are nowadays few studies demonstrating an increase of nitrotyrosine plasma level in patients during cardiac surgery. The relationship of these changes with postoperative complications and adverse outcomes has not been studied yet. Aim. The research was designed to investigate the dynamics of the nitrotyrosine plasma level in patients after cardiac surgery and assess its prognostic significance in terms of the development of early postoperative complications. Methods. The prospective observational cohort study involved 28 adult patients admitted at the cardiac intensive care unit of Moscow Regional Research and Clinical Institute (Moscow, Russian Federation). The relationship between the oxidative stress severity measured by intraoperative nitrotyrosine plasma levels and the development of acute kidney injury, cardiac failure and systemic inflammatory response syndrome was studied. Results. There was no significant perioperative dynamics of nitrotyrosine plasma levels when studying this oxidative stress marker in patients undergoing cardiac surgery. The level of nitrotyrosine plasma by the end of surgery was 12.1 [9.9; 13.0] nmol/mg of protein, which was 5% higher (p>0.5) than the initial level of 11.6 [9.3; 12.2] nmol/mg of protein, and returned to 11.5 [10.9; 12.4] after the 1 st postoperative day. The same perioperative dynamics occurred in the subgroups with different surgery techniques: valve surgery, œronary artery bypass grafting with cardiopulmonary bypass and off-pump œronary artery bypass grafting. Conclusion. The negative result achieved in this study might suggest that there are no significant changes of the perioperative nitrotyrosine plasma level in patients undergoing cardiac surgery, as well as that there is no significant correlation between the nitrotyrosine plasma level and the incidence of postoperative complications.