Effects of 60 minutes of hyperoxia followed by normoxia before coronary artery bypass grafting on the inflammatory response profile and myocardial injury

BACKGROUND: Ischemic preconditioning induces tolerance against ischemia-reperfusion injury prior a sustained ischemic insult. In experimental studies, exposure to hyperoxia for a limited time before ischemia induces a low-grade systemic oxidative stress and evokes an (ischemic) preconditioning-like effect of the myocardium. We hypothesised that pre-treatment by hyperoxia favours enchanced myocardial protection described by decreased release of cTn T in the 1(st) postoperative morning and reduces the release of inflammatory cytokines. METHODS: Forty patients with stable coronary artery disease underwent coronary artery bypass grafting with cardiopulmonary bypass. They were ventilated with 40 or >96% oxygen for 60 minutes followed by by 33 (18–59) min normoxia before cardioplegia. RESULTS: In the 1(st) postoperative morning concentrations of cTnT did not differ between groups ((0.44 (0.26-0.55) ng/mL in control and 0.45 (0.37-0.71) ng/mL in hyperoxia group). Sixty minutes after declamping the aorta, ratios of IL-10/IL-6 (0.73 in controls and 1.47 in hyperoxia, p = 0.03) and IL-10/TNF-α (2.91 and 8.81, resp., p = 0.015) were significantly drifted towards anti-inflammatory, whereas interleukins 6, 8and TNF-α and interferon-γ showed marked postoperative rise, but no intergroup differences were found. CONCLUSIONS: Pre-treatment by 60 minutes of hyperoxia did not reduce postoperative leak of cTn T in patients undergoing coronary artery bypass surgery. In the hyperoxia group higher release of anti-inflammatory IL-10 caused drifting of IL-10/IL-6 and IL-10/TNF-α towards anti-inflammatory.