Adenosine as cardioprotective in off-pump coronary artery bypass grafting

Objective
To assess the effect of adenosine as a cardioprotective drug and its role in attenuating ischemia-reperfusion injury during off-pump coronary artery bypass surgery.
Background
Cardioprotective drugs have long been investigated for use during off-pump coronary artery bypass surgery to attenuate ischemia-reperfusion injury and limit hemodynamic instability. Adenosine has been investigated due to its cardioprotective effect that is mediated through A1 and A3 adenosine receptors. Stimulation of these receptors reproduces the infarct-limiting effect of ischemic preconditioning.
Methods
After approval of the local ethics committee and informed written consent, fifty patients undergoing elective off-pump coronary artery bypass grafting were prospectively studied. The adenosine group received an infusion of Adenoscan at a rate of 50 μg/kg/min for 15 min. The control group received normal saline at the same rate and volume calculated. Pulmonary artery catheter was introduced through the right internal jugular vein. Cardiac output measurements were obtained. Cardiac index, stroke volume, systemic vascular resistance, pulmonary vascular resistance, right ventricular stroke work index, and left ventricular stroke work index were derived. Hemodynamic measurements were recorded together with blood levels of troponin I and CK-MB fraction to detect perioperative myocardial necrosis. Postoperative duration of mechanical ventilation, ICU stay together with inotropic support quantification using inotropic score were recorded.
Results
Fifty patients were included in the study. In the adenosine group, the infusion of adenosine resulted in a significant reduction in mean pulmonary artery pressure after stopping drug infusion (18 ± 2.2 mmHg versus 31 ± 4.1 mmHg). There was a recorded increase in cardiac index in the adenosine group that started 15 min after adenosine infusion and lasted for 12 h postoperatively ( < 0.001). Also, adenosine infusion resulted in a reduction in pulmonary vascular resistance that exceeded the reduction in systemic vascular resistance which resulted in a decrease in pulmonary vascular resistance/systemic vascular resistance ratio (0.14 in adenosine group 15 min after injection versus 0.28 in control group) and (0.11 in adenosine group 12 h postoperatively versus 0.26 in control group). The cTroponin I measured 6 h postoperatively was less in the adenosine group compared with the control group (5.8 ± 2.8 ng/ml versus 16.5 ± 3.9 ng/ml).
Conclusion
Adenosine infusion during off-pump coronary artery surgery may improve cardiac index, reduce the need for inotropes, and have cardioprotective effect.