Effect of Intraoperative Dexmedetomidine on Lung Protection Following Thoracic Aorta Surgery With Hypothermic Circulatory Arrest: a Randomized Clinical Trial

Patients will be divided into 2 groups; dexmedetomidine group and control group. Dexmedetomidine group will receive dexmedetomidine during and after thoracic artery surgery. And control group will receive the same amount of normal saline instead. Analyzing patients lung function and serum factors, which indicates the degree of systemic inflammatory responses and oxidative stress, The investigators will investigate the protective effect of dexmedetomidine on lung.