Risk Factors for Hypoxemia after Surgery for Acute Aortic Dissection

Objective To determine risk factors associated with postoperative hypoxemia after surgery for acute aortic dissection. Methods We retrospectively analyzed clinical data of 116 patients with acute aortic dissection who underwent endovascular stent-graft exclusion or open surgery in Qingdao Municipal Hospital from February 2007 to February 2012. All the 116 patients were diagnosed as acute aortic dissection by CT angiography(CTA),including 60 patients with Stanford type A aortic dissection and 56 patients with Stanford type B aortic dissection. According to whether they had postoperative hypoxemia,all the 116 patients with acute aortic dissection were divided into hypoxemia group[arterial partial pressure of oxygen(PaO 2 )/fraction of inspired oxygen(FiO 2 )200 mm Hg]:33 patients including 28 males and 5 females with their age of 52.7±11.4 years;and non-hypoxemia group(PaO 2 /FiO 2 ≥ 200 mm Hg):83 patients including 66 males and 17 females with their age of 55.0±13.8 years. Perioperative clinical data were analyzed and compared ‥ ‥between the two groups. Multivariate logistic regression was performed to identify risk factors of postoperative hypoxemia after surgery for acute aortic dissection. Results The incidence of postoperative hypoxemia after surgery for acute aortic dissection was 28.4%(33/116). Perioperative death occurred in 13 patients(11.2%,including 8 patients in the hypoxemia group and 5 patients in the non-hypoxemia group). Univariate analysis showed that preoperatively the percentages of patients with body mass index(BMI) 25 kg/m 2 ,smoking history,duration from onset to operation 24 h,preoperative PaO 2 /FiO 2 ≤ 300 mm Hg,and patients undergoing open surgery in the hypoxemia group were significantly higher than those in the non-hypoxemia group(P 0.05). Deep hypothermic circulatory arrest(DHCA)ratio,blood transfusion in 24 hours postoperatively,mechanical ventilation time,length of ICU stay and hospital stay in the hypoxemia group were significantly higher or longer than those in the non-hypoxemia group(P 0.05). Logistic multivariate regression identified BMI 25 kg/m 2 (OR=98.861,P=0.006),DHCA(OR=22.487,P=0.007),preoperative PaO 2 /FiO 2 ≤ 300 mm Hg (OR=9.080,P=0.037)and blood transfusion 6 U in 24 hours postoperatively(OR=32.813,P=0.003)as independent predictors of postoperative hypoxemia for open-surgery patients,while BMI 25 kg/m 2 (OR=24.984,P=0.036)and preoperative PaO 2 /FiO 2 ratio ≤ 300 mm Hg(OR=21.145,P=0.042)as independent predictors of hypoxemia for endovascular stent-graft exclusion patients. Conclusion Postoperative hypoxemia is a common complication after surgery for acute aortic dissection. Early interventions for obesity and preoperative hypoxemia,and reducing perioperative blood transfusion may decrease the incidence of postoperative hypoxemia after surgery for acute aortic dissection.