This is A prospective, randomized, placebo-controlled, reestimable adaptive clinical study to evaluate the efficacy and safety of perioperative application of sivelestat sodium to shorten the duration of postoperative invasive mechanical ventilation in acute type A aortic dissection patients with preoperative moderate and severe hypoxemia (PaO2/FiO2≤200mmHg).

In recent years, sivelestat sodium therapy has been used to treat and prevent CPB-associated lung injury with good results. Morimoto K et al., randomized control of a small sample size, demonstrated that sivelestat sodium improves respiratory function in patients with severe respiratory failure after hypothermia thoracic aortic surgery. A retrospective study by Morimoto N et al. confirmed that prophylactic application of sivelestat sodium at the beginning of CPB could improve postoperative respiratory function and shorten the duration of mechanical ventilation in patients with hypothermic circulatory arrest. At present, there is a lack of reliable RCTS to confirm that the intraoperative application of sivelestat sodium can effectively treat preoperative acute lung injury, improve CPB-related lung injury, and reduce the incidence of postoperative acute lung injury. Therefore, the objective of this study was to design A randomized controlled study to evaluate the clinical efficacy and safety of intraoperative use of sivelestat sodium to shorten the duration of postoperative invasive mechanical ventilation in acute type A aortic dissection patients with preoperative moderate to severe hypoxemia. The purpose of this preliminary clinical trial is to provide theoretical basis for sample size calculation of randomized controlled trials, and to evaluate the scientific nature and feasibility of randomized controlled trials.

Inclusion Criteria:

1. Aged 18-75;
2. Spontaneous acute (≤14 days) type A aortic dissection;
3. In the emergency department, hypothermic circulatory arrest combined with unilateral anterograde cerebral perfusion was expected to be performed on the aortic arch surgery;
4. Preoperative PaO2/FiO2≤200mmHg;

Exclusion Criteria:

1. Preoperative cardiogenic shock;
2. preoperative liver insufficiency;
3. Preoperative dissection involves important organs and seriously endangers the patient's life
4. Pregnant women;
5. hereditary connective tissue diseases, such as Marfan syndrome, Ehlers-Danlos syndrome, Loeys-Dietz syndrome, etc.;
6. Behcet's disease;
7. aortitis;
8. There is a history of neurologic disease that has been clearly diagnosed;
9. There is a history of a clearly diagnosed mental illness;
10. There is a definite diagnosis of chronic respiratory disease;
11. There is a clearly diagnosed immune disease;
12. There is a definite diagnosis of hematological diseases;
13. severe renal failure or require dialysis treatment;
14. Taking anti-inflammatory or anti-coagulant drugs within a week before admission;
15. People who are allergic to sivelestat sodium and other ingredients;
16. Has participated in other clinical trials;
17. The clinician judges that it is not suitable for inclusion in the study;