A CUSUM analysis of ruptured abdominal aortic aneurysm repair

Studies have investigated the role of hospital and surgeon case volume in outcome after ruptured abdominal aortic aneurysm repair (rAAA). Few have analyzed the learning curve of an individual surgeon. The purpose of this study was to analyze this learning curve in reducing morbidity and mortality after rAAA repair. Thirty-two consecutive patients who underwent rAAA repair during the initial 2.5 years of a vascular surgeon's career were reviewed retrospectively. They were divided temporally into two groups of 16 patients (groups 1 and 2). Outcome measures included mortality, postoperative myocardial infarction, stroke, and renal and respiratory failure. Perioperative variables previously associated with increased mortality were analyzed. The cumulative sum (CUSUM) method was used to analyze the learning curve with respect to published acceptable event rates and predetermined 80% alert and 95% alarm boundary lines. Groups 1 and 2 did not differ statistically in age, preoperative blood pressure, hemoglobin or creatinine. There was no difference in transfusion requirements (6.8 +/- 1.2 units vs. 6.4 +/- 1.0 units; p = 0.78), urine output (340 +/- 65 mL vs. 389 +/- 94 mL; p = 0.72) or clamp position. There was no difference in the incidence of postoperative myocardial infarction, stroke, or respiratory or renal failure. Thirty-day mortality in group 2 was 12% as compared to 50% in Group 1 (p = 0.03). On CUSUM analysis, the cumulative failure rate in group 2 progressed lower than the 80% reassurance line, indicating improved results with time. Mortality after rAAA repair decreased over time during an early period of an individual surgeon's career. The CUSUM method is a valuable tool in analyzing an individual surgeon's experience and shows promise in quality control in vascular surgery.