Lung ischemia-reperfusion injury in awake sheep: protection with verapamil

We caused unilateral lung ischemia-reperfusion injury in awake sheep by simultaneously occluding the left pulmonary artery and left main stem bronchus for 12 h. The occluded left lung was inflated with nitrogen. Reperfusion resulted in an elevation of lung lymph flow from 1.3 to 5.0 ml/15 min and an increase in lymph-to-plsma protein concentration ratios. Reperfusion, but not ischemia alone, caused an increase in wet-to-dry weight ratios in both the reperfused left lung and the contralateral right lung. Granulocytes increased in both lungs during the ischemic period and after reperfusion, and hypoxemia developed after reperfusion. The calcium channel antagonist, verapamil, given just before reperfusion, caused a marked attenuation in the reperfusion-induced changes in the lung lymph variables and wet-to-dry weight ratio. However, verapamil did not affect the hypoxemia or granulocyte sequestration seen after reperfusion. We conclude that reperfusion of ischemic sheep lung results in increased microvascular permeability that can be partially prevented by verapamil.