Remote preconditioning lessens the deterioration of pulmonary function after repeated coronary artery occlusion and reperfusion in sheep

Abstract

Purpose: We investigated whether remote organ preconditioning (RPC) can preserve pulmonary function following repeated myocardial ischemia/reperfusion in a model mimicking multi-vessel off-pump coronary artery bypass (OPCAB) revascularization. Methods: Nine sheep (Group-RPC) underwent RPC by three episodes of five-minute occlusion and five-minute reperfusion of the iliac artery. Five sheep (Group-C) were time-matched controls. Afterwards, ten-minute occlusion and reperfusion of the left anterior descending, the first diagonal and the left circumflex coronary arteries were performed consecutively. Hemodynamic and respiratory parameters and arterial blood gases were measured until 120 min after the final coronary reperfusion. Anesthesia was maintained with halothane in oxygen and nitrous oxide. Animals were ventilated with a tidal volume of 15-20 mL·kg-1 in a non-rebreathing system, and a respiratory rate 14-16 min, with 5-cm H2O positive end expiratory pressure after thoracotomy. Results: Repeated coronary occlusion and reperfusion was associated in this experimental model with an increase in pulmonary vascular resistance (PVR) and pulmonary arterial pressure (PAP) and a decrease in PaO2 and PaO2/FlO2 in Group-C. After 120 min reperfusion, PaO2 and PaO2/FlO2 in Group-RPC were higher (192 ± 69 mmHg and 241 ± 78 vs 115 ± 54 mmHg and 129 ± 64, P < 0.05), while PVR and PAP were lower than in Group-C. At 120 min of reperfusion, PaO2 and PaO2/FlO2 were inversely correlated with PVR (P < 0.01). Conclusions: RPC by transient occlusion of the iliac artery improves lung gas exchange after repeated coronary artery occlusion and reperfusion mimicking OPCAB surgery, and preserves low PVR in sheep.