Risk factors for postoperative death following elective surgical repair ofabdominal aortic aneurysm: results from the UK Small Aneurysm Trial

Background: In regional and population studies, the mortality rate within 3 0 days of elective surgical repair of abdominal aortic aneurysm is approxim ately 8 per cent. Identification of preoperative factors associated with th is mortality risk is important for informing surgical policy and may sugges t suitable preoperative interventions. Methods: In the UK Small Aneurysm Trial, 820 patients aged 60-80 years unde rwent elective open surgical repair of an abdominal aortic aneurysm. The re lationship between 30-day mortality rate and 13 prespecified potential prog nostic factors was investigated. The value of a published clinical predicti on rule was also evaluated. Results: The postoperative mortality rate was 5.6 per cent overall (46 deat hs in 820 patients), Postoperative mortality risk was significantly associa ted with older age (P=0.03), higher serum creatinine level (P=0.002) and lo wer forced expiratory volume in 1 s (FEV1) (P=0.003) in univariate analyses . Evidence of a relationship between age and postoperative death was weaken ed (P=0.08) after adjustment for creatinine level and FEV1. The predicted p ostoperative mortality risk ranged from 2.7 per cent in younger patients wi th below average creatinine levels and above average FEV1, to 7.8 per cent in older patients with above average creatinine levels and below average FE V1, The published clinical prediction rule did not validate wed on these da ta; observed risk did not correlate with predicted risk except for a small group of high-risk patients. Conclusion: Poor preoperative lung and renal function was strongly associat ed with postoperative death, Age was less important once these two importan t prognostic factors had been taken into account, The potential for preoper ative improvement in lung and renal function to reduce postoperative mortal ity rates should be addressed in future studies.