Effects of 60 Minutes of Hyperoxia Followed by Normoxia before Coronary Artery Bypass Grafting on the Inflammatory Response Profile and Myocardial Injury

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 1st 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 1st
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.