The Mechanism Research of Angiotensin II Pathway and Postoperative Hypoxemia
Conditions: Aortic Dissection
Sponsor: Beijing Anzhen Hospital

NCT05055570 
Document Date: March 1, 2022 
Relationship between postoperative hypoxemia and renin-angiotensin system in 
patients with stanford type A acute aortic dissection 
 
Study design 
This prospective observational study was approved by the Clinical Research Ethics 
Committee of Beijing Anzhen Hospital, Capital Medical University, Beijing, China 
(Identifier: 2021107X), registered at ClinicalTrials.gov (Identifier: NCT05055570), 
and performed from August 2021 to January 2022 at Beijing Anzhen Hospital, Capital 
Medical University, Beijing, China. 
Methods 
  The patient inclusion criteria included age 18-80 years old, diagnosis of Stanford 
type A aortic dissection, and scheduled for emergency surgery. The exclusion criteria 
included preoperative hypoxemia, perioperative acute cardiac insufficiency (left 
ventricular ejection fraction, LVEF < 40%) and rejection of consent. The overall study 
patients were divided into the hypoxemia group and non-hypoxemia group according 
to the presence or lack of hypoxemia after surgery. Postoperative hypoxemia is defined 
by the oxygenation index (OI), which is the ratio of arterial partial pressure of oxygen 
to fraction inspired oxygen (PaO2 / FiO2), of less than or equal to 200 for two 
consecutive times within the first 24 h after operation.  
Indicators and methods  
Basic characteristics, intraoperative details, biochemical parameters and outcome 
results were obtained, and blood was collected after surgery for the measurement of 
ANG II and sACE2 concentrations. All samples were tested twice by ELISA, and the 
average value was used for analysis. 
Statistical analysis 
Statistical analysis was performed using IBM SPSS software version 26.0. 
Univariate analysis was first performed to identify the potential risk factors for 
postoperative 
hypoxemia. 
Normally 
distributed 
continuous 
variables 
with 
homogeneous variance were compared using Student’s t test and otherwise using the 
Mann–Whitney U test. Categorical variables were compared using the chi-square test 

or Fisher’s exact test. Correlation analysis was performed using the Spearman rank 
correlation test. Multivariate logistic regression analysis was performed for factors with 
P < 0.1 or that were considered clinically important. The odds ratio (OR) was calculated 
with a 95% confidence interval (CI). A P value of less than 0.05 was considered 
statistically significant.