Predictors of Post Operative Respiratory Failure After Elective Open Abdominal Aortic Aneurysm (AAA) Repair

OBJECTIVES:
Post operative respiratory failure (PORF), defined as a requirement for mechanical ventilation >12 hours after surgery, occurs frequently in patients undergoing elective open AAA repair. Predictors and outcomes of PORF in this population are not well-defined. This study seeks to examine the incidence of PORF, to identify significant patient and operative characteristics associated with PORF, and to describe the impact of PORF on mortality and resource utilization.
METHODS:
We reviewed all elective open AAA procedures prospectively entered into the Vascular Study Group of Northern New England database (n=1110) between January 1, 2003 and December 31, 2008. Univariate predictors of PORF were included in a multivariable logistic regression model that adjusted for individual institutional volume.
RESULTS:
Time to extubation was recorded in 1105 (99.6%) patients, of whom 198 (17.8%) experienced PORF. Univariate analysis identified multiple demographic factors, patient risk factors, and intraoperative factors that were significantly associated with PORF (Table 1a). In multivariable analysis, female gender, older age, chronic obstructive pulmonary disease (COPD), longer procedure duration, greater crystalloid requirement, and suprarenal clamp position increased risk for PORF; previous CABG/PTCA and mannitol administration were protective (Table 1b). PORF was associated with longer mean hospitalization (17.6 vs. 8.0 days, p<0.0001) as well as increased mortality at 30 days (6.6% vs. 1.1%, p<0.0001) and at 1 year (11.1% vs. 3.0%, p<0.0001).
CONCLUSIONS:
In this large, multicenter cohort of patients undergoing open AAA repair, age>80, female gender, history of COPD and surgical complexity were the dominant determinants of PORF. Prompt identification of these high risk patients is important as they are at significantly increased risk of perioperative and 1-year mortality.