Study On The Risk Factors Of Aortic Dissection And Postoperative Hypoxemia

The aorta is the largest blood vessel in the human body.It starts from the left ventricle,moves upward,backward and then downward,and goes down along the left side of the spine.It is divided into bilateral common iliac arteries in the abdominal cavity.Along the way,it branches out several branches to supply blood for various organs.The aorta can be divided into ascending aorta,aortic arch and descending aorta.The descending aorta is divided into thoracic descending aorta and abdominal aorta by the diaphragm.The aorta is an elastic artery,which is characterized by rich elastic fibers and collagen fibers,and can withstand high blood pressure.The aortic wall can be divided into: 1.The thickness of the intima: about 100-130 um,accounting for about one-sixth of the total thickness of the aortic wall.It is mainly composed of endothelial cells.The inner skin cells contain plasma membrane vesicles,and contain varying amounts of microfilaments.The vesicles contain a variety of molecules that are actively transported.Endothelial cells are connected by tight and spaced slit tubes.The basement membrane is thin and finely reticulated.The subendothelial layer contains loose connective tissue,elastic fibers,scattered fibroblasts and some longitudinal smooth muscle cells.Under light microscope,the inner elastic membrane has no obvious boundary.Under electron microscope,the first layer adjacent to the intima is the inner elastic membrane.2.Medial membrane: about 500 um thick,which is the thickest layer of the aortic wall.It is composed of multiple layers of elastic membranes.Each layer of elastic membrane is connected by elastic fibers.Elastic fibers and collagen fibers connect and fix slender smooth muscle cells on the elastic membrane.3.Outer membrane: It is composed of elastic fibers and collagen fiber bundles in longitudinal or spiral arrangement,including fibroblasts,mast cells and a small number of smooth muscle cells in longitudinal arrangement.The outer membrane is difficult to identify under light microscope,and can be seen under electron microscope as the elastic fiber membrane in intermittent arrangement adjacent to the outer layer of the middle membrane.When the resistance of the aortic wall is reduced(atherosclerotic ulcer or Marfan syndrome and other genetic diseases)or the shear force applied on the aortic wall is increased,the intima of the aorta is broken,and the blood flow rapidly rushes into the middle membrane and tears longitudinally along the long axis of the artery,resulting in the separation of the inner membrane and the outer membrane.The aortic lumen is divided into true lumen and false lumen,that is,aortic dissection.Aortic dissection is most commonly seen in65-75 patients,men outnumber women,about 2:1,but women are more likely to have atypical symptoms,which will lead to delayed diagnosis and treatment,leading to higher mortality.It is reported that the incidence rate of aortic dissection is 3-5 cases per 100000 people every year,because there is no report of death before admission and undiagnosed patients in basic hospitals,Therefore,this data may underestimate the incidence rate of aortic dissection.Aortic dissection is one of the most dangerous and urgent cardiovascular diseases.It is reported that the risk of death of patients with aortic dissection without diagnosis and formal treatment increases by 1% per hour,and the highest rate of death can reach 70% within one week.In recent years,the number of young patients with aortic dissection has increased year by year in China,resulting in increasing social pressure and family pressure.In 1965,DeBakey defined the classification of aortic dissection for the first time according to the location and extent of the rupture of aortic dissection;Type Ⅱ: the rupture is located in the ascending aorta,and the range of involvement is limited to the ascending aorta;Type Ⅲ: The dissection rupture is located far from the left subclavian artery,and the range of involvement is the thoracic descending aorta and abdominal aorta far from the left subclavian artery.In order to better guide clinical treatment,Daily classified DeBakey Type Ⅰ and Type Ⅱ as Stanford A in 1972,and DeBakey Type Ⅲ as Stanford B in 1972.Since then,the classification is simpler and more conducive to guide clinical treatment.The etiology of aortic dissection is complex.It is currently recognized that it includes hypertension,atherosclerosis,genetic factors,trauma and anatomical factors.However,the literature reports that its risk factors are diverse,such as gender,climate,nicotine intake,cocaine intake,previous heart disease history,and inflammatory diseases.Therefore,it is difficult to determine the etiology and diagnosis.Moreover,because aortic dissection involves many vessels and has various pathological conditions,it is difficult to diagnose and easy to cause misdiagnosis.According to statistics,due to the huge differences in medical resources and technical equipment in different regions,the diagnosis of aortic dissection has different degrees of delay.It is reported that the median time from onset to diagnosis of aortic dissection is5-29 hours,especially for women The elderly and patients with undiagnosed genetic diseases are more prone to misdiagnosis and mistreatment.At present,Stanford type A aortic dissection is still dominated by surgery,including half arch replacement,full arch replacement and other surgical methods.The guidelines recommend that non-complex Stanford type B aortic dissection is dominated by drug treatment,while complex Stanford type B aortic dissection is dominated by endovascular treatment.Since active vein dissection is easy to affect the chest and lungs,no matter what treatment method,there is a certain incidence rate of postoperative hypoxemia,According to the literature,the highest incidence rate is 40%,which seriously affects the time of tracheal intubation and hospitalization in ICU.The incidence of pulmonary infection,multiple intubations and other complications is significantly higher,and the medical cost and patients’ family burden are sharply increased.The purpose of this study is to identify the difference factors between Stanford A and Stanford B aortic dissection through statistical analysis of the general data of patients with aortic dissection,laboratory results and surgical and treatment-related data,and to guide clinical early prevention and intervention by analyzing the relevant risk factors of postoperative hypoxemia.Part 1 Analysis of pathogenic factors and hypoxemia subgroup differences between Stanford type A and Stanford type B aortic dissectionObjective: The purpose of this study is to provide a basis for early diagnosis,differential diagnosis and understanding of the pathogenesis of Stanford A and Stanford B aortic dissection by comparing the differences in the pathogenic factors of Stanford A and Stanford B aortic dissection and analyzing the risk factors that lead to hypoxemia after surgery.At the same time,through the analysis of the differences in the risk factors of hypoxemia between the two types of aortic dissection,we can early find patients with high risk of hypoxemia,To provide basis for early clinical intervention.Methods: This study collected the clinical data of 125 hospitalized patients with Stanford A aortic dissection and 200 hospitalized patients with Stanford B aortic dissection from January 2019 to December 2021 in the First Hospital of Hebei Medical University,including 60 patients with hypoxemia in Stanford A aortic dissection group and 49 patients with hypoxemia in Stanford B aortic dissection group,The data of laboratory results and surgical treatment were also compared between the two groups in terms of pathogenic factors and risk factors of postoperative hypoxemia.Results: By comparing the relevant medical history and clinical data of Stanford type A and Stanford type B aortic dissection at the time of onset,it was found that there were significant differences between the two in terms of gender,mainly male patients.There were significant differences in heart rate,systolic blood pressure and diastolic blood pressure of both upper limbs between the two groups,and Stanford type B dissection was significantly higher(P<0.001).Comparing the results of the two groups,it was found that the two groups had significant differences in white blood cell count,C-reactive protein,total cholesterol,low-density lipoprotein and high-density lipoprotein.The white blood cell count of Stanford type A aortic dissection was significantly higher than that of Stanford type B aortic dissection(P<0.001).The C-reactive protein,total cholesterol,low-density lipoprotein and high-density lipoprotein of Stanford type B aortic dissection patients were significantly higher than those of Stanford type A aortic dissection(P<0.001).By comparing the treatment related treatments of the two groups,it was found that the hospitalization days,ventilator use time and ICU hospitalization time of Stanford type A aortic dissection were significantly higher than those of Stanford type B aortic dissection(P<0.001).Comparing the proportion of hypoxemia in patients with Stanford type A aortic dissection and Stanford type B aortic dissection,it was confirmed that the incidence of hypoxemia in Stanford type A aortic dissection was significantly higher(P<0.001).Further comparison of the demographic and clinical data of the two groups of patients with hypoxemia showed that the proportion of smoking in patients with Stanford B aortic dissection hypoxemia was significantly higher than that in patients with Stanford A(P<0.001).There were significant differences between the two groups in the past maximum systolic blood pressure,bilateral upper limb systolic blood pressure and diastolic blood pressure(P<0.001).The results of the two groups were the same as those of the preceding pathogenic factors.There were significant differences between the two groups in white blood cell count,C-reactive protein,total cholesterol,low-density lipoprotein,high-density lipoprotein,hospital stay,intubation time,and ICU hospital stay(P<0.001).Conclusion: The incidence of Stanford type A and Stanford type B aortic dissection is related to hypertension and hyperlipidemia,and both hypertension and hyperlipidemia are related to the incidence of postoperative hypoxemia.Part 2 Metabolic syndrome and its components are associated with hypoxemia after surgery for acute type A aortic dissectionObjective: The aim of this study was to explore whether or to what extent metabolic syndrome(METs)and its components were associated with hypoxemia in acute type A aortic dissection(ATAAD)patients after surgery.Methods:This study involved 271 inpatients from the first hospital of He Bei medical university between 2018.6 and 2021.10 who underwent surgery.Demographic and clinical data were collected.Subgroup analysis,mixed model regression analysis,and receiver operating characteristic(ROC)curve analysis were performed,and a scoring system was evaluated.Results: The 271 inpatients were assigned to the hypoxemia group(n=48)or no hypoxemia group(n=223)regardless of METs status.Compared to the no hypoxemia group,the hypoxemia group had a higher incidence of METs.Hypoxemia was present in 0%,3.7%,19.8%,51.5%,90.0% and 100% in the groups of individuals who met the diagnostic criteria of Met S 0,1,2,3,4 and5 times,respectively.In the multivariable logistic regression analysis,BMI quartile was still a risk factor for hypoxemia after adjustment for other risk factors.After adjustment for potential confounding factors,METs was an independent risk factor for hypoxemia in several models.After assigning a score for each METs component present,the AUCs were 0.852(95% CI0.789–0.914)in all patients,0.728(95% CI 0.573–0.882)in patients with METs and 0.744(95% CI 0.636–0.853)in patients without METs according to receiver operating characteristic analysis.Conclusions: METs,especially body mass index,confers a greater risk of hypoxemia in ATAAD after surgery.Part 3 Analysis of risk factors related to hypoxemia after Stanford B aortic dissectionObjective : This study analyzed the correlation between preoperative general data,laboratory results and surgical related factors of patients with Stanford B aortic dissection and postoperative hypoxemia,and explored the risk factors of postoperative hypoxemia in patients with Stanford B aortic dissection.Methods:This study collected the general data,preoperative laboratory results and operation-related variables of 120 patients with Stanford B aortic dissection without basic respiratory system disease in the vascular surgery department of the First Hospital of Hebei Medical University from January2019 to December 2021,and divided them into hypoxemia group(49 cases)and non-hypoxemia group(71 cases)according to whether there was hypoxemia after operation,The related factors and independent risk factors of postoperative hypoxemia were inferred through univariate analysis and logistic regression analysis,and the risk ratio was estimated.Results : According to whether the patients had hypoxemia after operation,Stanford B type aortic dissection patients were divided into hypoxemia group(49 cases)and non-hypoxemia group(71 cases).The general medical history and other data of the patients in the two groups,preoperative laboratory results and operation-related variables were collected.The results of univariate analysis showed that the age of patients in the hypoxemia group was significantly higher than that in the non-hypoxemia group,and the difference was statistically significant(P<0.05).Further analysis of other data confirmed that the left upper limb diastolic pressure and alanine aminotransferase in the hypoxemia group were significantly higher than those in the non-hypoxemia group,and the difference was statistically significant(P<0.05).Analyze the treatment-related variables of patients in the hypoxemia group and the non-hypoxemia group,and confirm that the time of tracheal intubation and ICU hospitalization in the hypoxemia group are significantly higher than those in the non-hypoxemia group,and the difference is statistically significant.Further logistic regression analysis showed that left upper limb diastolic pressure was an independent risk factor for hypoxemia after Stanford B aortic dissection(95% CI 1.002-1.057).Conclusions:Age,alanine aminotransferase and left upper limb diastolic pressure have significant effects on hypoxemia after Stanford B aortic dissection,and left upper limb diastolic pressure is an independent risk factor for hypoxemia after Stanford B aortic dissection.Postoperative hypoxemia seriously affects the time of tracheal intubation and the length of stay in ICU,which requires special attention.