Aortic dissection (AD) is one of the most dangerous cardiovascular emergencies, with rapid onset, rapid progression, high fatality rate, and a variety of life-threatening complications. Acute lung injury (ALI) caused by AD is an important cause of many adverse outcomes. Studies have confirmed that 34.9% to 53.8% of AAD patients have ALI before surgery, and Impaired preoperative lung function may lead to worse oxygenation after AD surgery. The pathophysiological mechanism of AD-induced ALI is complex. A variety of preoperative and intraoperative risk factors can induce or aggravate ALI, such as ischemia-reperfusion injury, deep hypothermic circulatory arrest, and inflammatory reactions. At present, the clinical use of improved surgery, cardiopulmonary bypass perfusion, early anti-inflammatory treatment, and protective lung ventilation can reduce and improve perioperative ALI to a certain extent, but it is still not ideal. In recent years, inhibition of neutrophil activation and aggregation, and reduction of neutrophil elastase activity as targets for the treatment of inflammatory injury have also become an important clinical treatment measure, in order to further reduce the body's inflammatory response to improve and alleviate ALI. Sivelestat sodium, as a neutrophil elastase inhibitor, is the only approved therapeutic drug for ALI/ acute respiratory distress syndrome (ARDS) in the world. It is precisely by reducing the inflammatory infiltration of neutrophils and inhibiting neutrophil elastase activity, thereby exerting a certain protective effect on the lungs. The study takes patients with AD surgery as the research object. On the basis of not terminating and changing the original treatment plans, sivelestat sodium was added in the perioperative period to observe the incidence, and severity of ALI/ARDS in the perioperative period. It aims to explore the efficacy and safety of sivelestat sodium in the treatment of pulmonary insufficiency after AD arch surgery under hypothermic circulatory arrest.

The study is a single-center, randomized, open-label, blank-controlled study, and designs to recruit AD perioperative patients admitted to the Cardiovascular Surgery Department of the First Affiliated Hospital of Xi'an Jiaotong University, between January 1, 2022 and December 31, 2022, with a total of 168 cases. After the patients who met the inclusion and exclusion criteria signed the informed consent, they were randomly assigned to the experimental group and the control group at a 1:1 ratio, with 84 cases in each group. The experimental group is additionally given sivelestat sodium in the perioperative period on the basis of the original treatment. The study was divided into two phases, the screening phase and the treatment phase. The screening period was from admission to the day of surgery to determine whether patients were suitable for the study. The treatment period is from the induction of anesthesia to the day of being transferred out from the ICU. It is necessary to complete the detailed treatment plan, and drug dosage, intraoperative and postoperative serological examinations, imaging examinations, and the patient's mechanical ventilation and oxygenation index data. Sivelestat sodium was used during and after operation in the experimental group, and the end time of administration was 96 hours after admission to the ICU. During the treatment with sivelestat sodium, the patient's original treatment plan will not be terminated or affected. The control group only received the original clinical diagnosis and treatment and clinical management. Study endpoints were defined as the day of ICU transfer, follow-up until discharge, or discontinuation/termination during the study period, or patient withdrawal from the study for any reason. During the study period, doctors will provide supportive treatment according to clinical indications, medication instructions and specifications. In the event of an adverse event, the doctor may make adjustments to the medication dose and treatment duration. The main observation indicators were the incidence of moderate to severe respiratory insufficiency (PaO2/FiO2 ≤ 200mmHg) at 24, 72, and 120 hours after surgery, on the day of transfer out of ICU, and discharge. The efficacy and safety of the drug were evaluated.

Inclusion Criteria:

• Patients aged from 18 to 70 years old;
• Patients undergoing aortic dissection arch surgery under hypothermic circulatory arrest;
• Weight from 45 to 90kg;
• ASA cardiac function class from II to IV;
• Patients who can understand and comply with the requirements of the protocol and volunteer to participate.

Exclusion Criteria:

• Patients participating in other clinical studies;
• Patients with serious lack of medical data;
• Women who are pregnant or may become pregnant or breastfeeding;
• Patients with severe lung diseases, such as end-stage chronic obstructive pulmonary disease, chronic interstitial lung disease, etc.;
• Patients with malignant tumors;
• Preoperative oxygenation index PaO2/FiO2≤200mmHg;
• Patients with EUROScoreII mortality risk < 3%;
• Patients with APACHE II score ≥ 21;
• Patients who are judged by the researchers to be unsuitable for inclusion, such as those with mental illnesses.