Abstract:

Objective To investigate the protective effects of lung ischemic preconditioning in deep hypothermic circulatory arrest (DHCA) on lung tissues. Methods Eighteen piglets were randomly divided into ischemic preconditioning group (n=6), joint preconditioning group (ischemic and anoxemic preconditioning, n=6) and control group (no preconditioning, n=6). Values of lung static compliance, pulmonary vascular resistance index, lung wet weight to dry weight ratio and left atrium to pulmonary artery ratios of plasma tumor necrosis factor-α (TNF-α), interleukin (IL)-8 and IL-10 levels (relative contents of TNF-α, IL-8 and IL-10) before and after cardiopulmonary bypass were measured in each group, and lung tissues were harvested for observations of pulmonary edema and inflammatory cell infiltration under light microscopy with HE staining. Results There was no significant difference in each parameter among groups before cardiopulmonary bypass. After cardiopulmonary bypass, lung static compliance of joint preconditioning group was higher than that of the other two groups (P<0.05), pulmonary vascular resistance index and relative contents of IL-8 and IL-10 in ischemic preconditioning group and joint preconditioning group, and lung wet weight to dry weight ratio in joint preconditioning group were significantly lower than those of control group (P<0.05). Compared with those before cardiopulmonary bypass, lung static compliance decreased, lung wet weight to dry weight ratio increased, and relative contents of TNF-α, IL-8 and IL-10 increased in three groups after cardiopulmonary bypass (P<0.05 for all), and pulmonary vascular resistance index increased in control group and ischemic preconditioning group (P<0.05), while there was no significant difference in pulmonary vascular resistance index before and after cardiopulmonary bypass in joint preconditioning group (P>0.05). Histological observations indicated that the pulmonary edema and inflammatory cell infiltration in joint preconditioning group were less severe than those in the other two groups. Conclusion Lung ischemic preconditioning may reduce ischemic reperfusion injury during DHCA, and lung ischemic and anoxemic preconditioning may yield better protective effects than single ischemic preconditioning.

Key words: cardiopulmonary bypass, deep hypothermic circulatory arrest, preconditioning, lung ischemic preconditioning, ischemic reperfusion injury