Cardiac ischemic preconditioning improves lung preservation in valve replacement operations

Abstract

Background. Previous work has shown that cardiac ischemic preconditioning reduces cardiac reperfusion injury. We investigated whether cardiac ischemic preconditioning can improve lung preservation in patients who undergo valve replacement. Methods. Forty patients with rheumatic heart disease requiring valve replacement were randomly divided into two groups. Twenty patients received two cycles of 3 minutes of aortic cross-clamping and 2 minutes of reperfusion before cardioplegic arrest (group IP), and 20 patients underwent 10 minutes of cardiopulmonary bypass (group C, control group). Blood samples from the pulmonary vein were collected to measure levels of polymorphonuclear leukocytes, superoxide dismutase, malonedialdehyde, and thromboxane B 2, and arterial oxygen tension. Blood samples from the coronary sinus were used to measure calcitonin gene–related peptide values. Hemodynamic data were recorded by a pulmonary artery Swan-Ganz catheter. Lung tissue was collected after 1 hour of reperfusion to evaluate morphology. Clinical outcome data were recorded. Results. In group C (cardiopulmonary bypass and cardioplegic arrest), the levels of polymorphonuclear leukocytes, thromboxane B 2, malonedialdehyde, and calcitonin gene–related peptide were increased after 1 hour of reperfusion, whereas the value for superoxide dismutase was decreased. In group IP, preconditioning attenuated the increase in polymorphonuclear leukocytes, thromboxane B 2, and malonedialdehyde ( p < 0.05) and increased superoxide dismutase and calcitonin gene–related peptide levels ( p < 0.05). Preconditioning also increased arterial oxygen tension and cardiac index compared with controls ( p < 0.05) and decreased mean pulmonary artery pressure and pulmonary vascular resistance index ( p < 0.05). Histologic findings showed less lung injury and a lower polymorphonuclear leukocyte count in group IP than in group C ( p < 0.05). Group IP had fewer postoperative pulmonary complications and a shorter intubation time. Conclusions. Cardiac ischemic preconditioning improves lung preservation in patients having valve replacement. The mechanism may be that cardiac ischemic preconditioning reduces the accumulation of polymorphonuclear leukocytes in lung tissue and decreases the formation of oxygen free radicals.Key Words: Ischemic preconditioning; lung injury; open heart surgery; calcitonin gene–related peptide.