The relationship between volume and outcome following elective open repair of abdominal aortic aneurysms (AAA) in 131 German hospitals.

OBJECTIVES

Several studies indicate that high-volume hospitals have better results in open repair of unruptured abdominal aortic aneurysms (AAA). Up to now no studies had addressed this question in German hospitals.

DESIGN

Post-hoc-analysis from a prospective physician-led registry.

MATERIAL AND METHODS

Since 1999, the German Society for Vascular Surgery has conducted a prospective registry for open and endovascular repair of AAAs. This study includes 131 hospitals who conducted n=10163 elective open repairs for unruptured AAA between 1999 to 2004. All perioperative variables including annual volume as a continuous variable were analysed in a step-wise logistic regression model. In order to define a threshold annual volume an additional logistic regression analysis was performed by use of annual volume groups (0-9, 10-19, 20-29, 30-39, 40-49, 50 or more). The relationship between annual volume and further outcome parameters (length of procedure, blood transfusion, length of stay) were also analyzed.

RESULTS

The overall mortality rate was 3.2%. The stepwise logistic regression model identified the following predictors of an increased perioperative mortality: age (OR 1.084, 95% CI 1.066-1.102), AAA diameter (OR 1.008, 95% CI 1.001-1.016), length of procedure (OR 1.008, 95% CI 1.006-1.009), ASA-Score (OR 2.636, 95% CI 2.129-3.264), suprarenal clamping (OR 1.447, 95% CI 1.008-2,078), blood transfusion (OR 1.786, 95% CI 1.268-2.514). Annual volume was moderately predictive (OR 1.003, 95% CI 1-1.006) but failed to reach statistical significance (p=0.07). The analysis of volume groups identified a significantly higher risk for hospitals with an annual volume of 1-9 AAA-repairs by comparison to hospitals with an annual volume of 50 or more AAA-repairs (OR 1.903, 95% CI 1.124-3.222). Operations at low volume hospitals were also longer (p<0.001), with an extended postoperative stay (p<0.001) and a higher transfusion rate (p<0.001).

CONCLUSIONS

Patient's age, ASA classification, AAA diameter, length of procedure, suprarenal clamping and blood transfusion are predictive variables for an increased perioperative mortality in elective open AAA repair. Mortality is also increased by a low annual volume. Further studies are needed to examine whether these data are applicable to all German hospitals.