Intermittent Normoxia Reduces Myocardial Reperfusion Injury

This study aims to determine the effect of intermittent normoxic cardiopulmonary bypass (CPB) on inflammatory response, oxidative stress and myocardial reperfusion injury in adult patients undergoing valve replacement. The investigators hypothesized that nuclear factor kappa B (NFkB) was involved in regulating gene expression of myocardial inflammatory factor.

Methods:Patients meeting the requirement will be randomized into 2 groups: the control group received hyperoxic reperfusion (PaO2 180-250 mmHg) throughout CPB as routine; the treatment group underwent 3 cycles of 5/5 min normal/high oxygenation (PaO2 80-150/180-250 mmHg) during cardioplegia arrest, and maintained the same hyperoxia as the control group in the rest time of CPB. The clinical data of inotropes requirement, drainage, ventilation and intensive care time will be recorded. Venous blood samples will be taken perioperatively for detecting concentration of troponin I (cTnI), tumor necrosis factor-α , interleukin-6, 10, and malondialdehyde (MDA). Atrial biopsies will be removed before cardioplegia arrest and 30min after aortic de-clamping to determine the extent of neutrophil infiltration (myeloperoxidase activity), NFkB binding DNA activity, and gene expression of inflammatory factors (TNF-α, IL-6, 10). Statistical analysis:A sample size of at least 32 patients in each group was needed to have a power of 90%, significance at the two-side 5% level, on the basis that a SD of 0.2 ng/ml and a difference in peak serum cTnI release of about 0.15 ng/ml between control and conditioned patients was determined. Expected Results: The treatment group will have significantly lower release of cTnI, inflammatory factors, and MDA during CPB and afterwards. Intermittent normoxia may be related to less myocardial inflammation characterized by decreased myeloperoxidase activity, gene expression of inflammatory factors, the later may result from reduced activity of NFkB binding to DNA after reperfusion.