IngentaConnect Pre-treatment with hyperoxia before coronary artery bypass grafti...

Abstract:

Background:

In experimental studies, exposure to hyperoxia for a limited time before ischaemia induces a low-grade systemic oxidative stress and evokes an (ischaemic) preconditioning-like effect of the myocardium. We hypothesised that hyperoxia before cardioplegia could protect the myocardium against necrosis and stunning caused by ischaemia-reperfusion. Methods:

Forty patients undergoing coronary artery bypass grafting were randomly exposed to an oxygen fraction of 0.4 or >0.96 in inspired air on an average of 120 min before cardioplegia. Blood for troponin I, creatine kinase-MB, lactate, glutathione and interleukin-6 was sampled from arterial and coronary sinus cannulae during 20 min of reperfusion. Additional arterial samples were drawn 60 min after declamping and in the first post-operative morning. The cardiac index and right and left ventricular stroke work indices were measured before sternotomy and up to 12 h post-operatively. Results:

Troponin I, creatine kinase-MB and lactate did not differ between the groups. Hyperoxic pre-treatment had no impact on the post-operative haemodynamic indices measured with the thermodilution pulmonary artery catheter. More oxidised glutathione was released in the hyperoxia group in the first minute of reperfusion (P = 0.015). Hyperoxic pre-treatment abolished the myocardial release of interleukin-6 during 20 min of reperfusion (P = 0.021 vs. controls). In the first post-operative morning, interleukin-6 was higher in the hyperoxia group [127.0 (86.0-140.0) vs. 85.2 pg/ml (66.6-94.5 pg/ml); P = 0.016]. Conclusions:

Exposure to >96% oxygen before cardioplegia did not attenuate ischaemia-reperfusion injury of the heart in patients undergoing coronary artery bypass grafting. The only potentially beneficial effect observed was the decreased transmyocardial release of interleukin-6.

Keywords: Coronary artery bypass grafting; creatine kinase-MB; glutathione; hyperoxia; ischaemia-reperfusion; preconditioning; stunning; troponin I

Document Type: Research article

DOI: 10.1111/j.1399-6576.2007.01444.x

Affiliations: 1: North Estonia Regional Hospital, Clinic of Anaesthesiology, Tallinn 2: Institute of Biochemistry, University of Tartu, Tartu 3: 4North Estonia Regional Hospital, Centre of Cardiothoracic Surgery, Tallinn, Estonia 4: Clinic of Anaesthesiology and Intensive Care, University of Tartu, Tartu

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Pre-treatment with hyperoxia before coronary artery bypass grafting - effects on myocardial injury and inflammatory response