Surgeon volume and in-hospital mortality for open AAA repair

Researchers from Southwestern Texas University's Division of Vascular and Endovascular Surgery and the Veterans Medical Center, both in Dallas, have reported that composite surgeon (overall) volume rather than operation-specific (annual) surgeon volume is a key determinant of in-hospital mortality for elective open abdominal aortic aneurysm surgery (AAA). Their research was published in the December issue of the Journal of Vascular Surgery®.

According to study co-author J. Gregory Modrall, MD, who now is a professor of surgery and a vascular surgeon at the University of Arkansas for Medical Sciences in Little Rock, prior studies only reported improved clinical outcomes with higher surgeon volume, which was assumed to be a product of the surgeon's experience with the index operation.

"We analyzed approximately 111,533 records of patients who had elective open AAA surgery performed by 6,857 surgeons between 2000 and 2008," said Dr. Modrall. "The surgeons were stratified into deciles based on operation-specific volume and composite volume. Composite volume was defined by the total number of several open vascular operations: carotid endarterectomy, aortobifemoral bypass, femoral-popliteal bypass, and femoraltibial bypass. Multiple logistic regression analyses were used to examine the relationship between surgeon volume and in-hospital mortality for open AAA repair, adjusting for patient and hospital characteristics."

The crude in-hospital mortality rate over the study period was 6.1 percent (95 percent CI, 5.6 percent-6.5 percent). The mean number of open AAA repairs performed annually was 2.4 operations per surgeon. The mean composite volume was 5.3 operations annually. As expected, in-hospital mortality for open AAA repair decreased with increasing volume of open AAA repairs performed by a surgeon. Mortality rates for the lowest and highest deciles of surgeon volume were 10.2 percent and 4.5 percent, respectively.

A similar pattern was observed for composite surgeon volume, as the mortality rates for the lowest and highest deciles of composite volume were 9.8 percent and 4.8 percent, respectively. After adjusting for patient and hospital characteristics, increasing composite surgeon volume remained a significant predictor of lower in-hospital mortality for open AAA repair (odds ratio, 0.994; 95 percent, confidence interval, .992-.996), whereas increasing volume of AAA repairs per surgeon did not predict in-hospital deaths.

"These data suggest that composite case numbers may be a more valid criterion than operation-specific case numbers," added Dr. Modrall. "Whether this finding may be generalized to other open and endovascular procedures should be clarified and be considered for future credentialing of surgeons."