The Effect of Extracorporeal Circulation on Oxidative Stress and Viscosity

Objective: One of the main determinants of morbidity and mortality after cardiopulmonary bypass (CPB) and its associated extracorporeal circulation (EC) is the oxidant stress that occurs during and after the procedures. There are unknowns about mechanisms that need to be revealed. This study aimed to examine the effecs of EC on oxidant, antioxidant parameters, and viscosity. Methods: The study was carried out in 22 patients between the ages of 42 and 70 undergoing Coronary artery bypass grafting. Blood was drawn at seven different stages of the operation, including A: Pre-operative intensive care stage, B: Anesthesia, C: Connecting to the pump, D: After aortic cross-clamp, E: Release of the aortic cross-clamping, F: Disconnection from the pump, and G: Post-operative intensive care. Malonyldialdehyde (MDA) and Nitrite + Nitrate (NOx) levels were measured in terms of oxidant stress, and total sulfhydryl group (RSH) levels as an antioxidant indicator. Furthermore, plasma viscosity at each stage was measured. Results: At the C stage, NOx and MDA levels increased, and RSH levels began to decrease. The highest MDA, NOx, and lowest RSH levels were detected in the F stage. Viscosity was also decreased after connection to the pump and increased after pump disconnection. Conclusion: MDA and RSH levels were compatible with oxidant stress and antioxidant capacity reduction, respectively, caused by surgical trauma and non-physiological surfaces of EC. One of the reasons for the increase in NOx levels is the mechanical stimulation of the endothelium as a result of surgical procedures. Another reason may be that the erythrocytes circulating on the artificial surfaces of EC are exposed to mechanical stress and their eNOS expression. The decreased viscosity develops due to hemodilution and plasma protein denaturation.