Friday, November 28, 2003

Beat to the punch again by DB with this post on the impact of surgeon volume on mortality. The original paper appeared in the November 27th New England Journal of Medicine. The authors reviewed the records of 474,108 patients that had one of eight procedures done during 1998-1999. The procedures were: carotid endarterectomy, aortic valve replacement, coronary artery bypass grafting, esophagectomy, cystectomy, pancreatectomy (for cancer), lung resection, and elective aortic aneurysectomy. The goal of the study was to try to measure the impact of the experience of the surgeon on outcomes, separate from the experience of the hospital.
What they found was that the volume of the surgeon and the volume of the hospital affected procedure outcomes differently based on the procedure:

When surgeon volume was assessed as a continuous variable, it was inversely related to operative mortality for all eight procedures (P=0.003 for lung resection, P<0.001 for all other procedures). The strength of the inverse association between surgeon volume and outcome varied markedly according to the procedure in terms of both the absolute operative mortality rate and the adjusted odds ratio for operative death .....When hospital volume was assessed as a continuous variable, it was inversely related to operative mortality for seven of the eight procedures (P=0.20 for carotid endarterectomy, P<0.001 for all the other procedures). After adjustment for surgeon volume, however, higher hospital volume remained a significant predictor of decreased mortality for only four procedures (repair of an abdominal aortic aneurysm, cystectomy, lung resection, and pancreatic resection).

Or in other words:

It is not surprising that the relative importance of surgeon volume and hospital volume varies according to the procedure. In the case of carotid endarterectomy, for example, technical skill and the use of specific intraoperative processes (e.g., intraarterial shunt insertion and patch angioplasty)21 — processes used at the discretion of the operating surgeon — are important determinants of the risk of operative stroke or death. In contrast, other hospital-based services are relatively less important. Most patients undergoing carotid endarterectomy do not require intensive postoperative management, and the length of stay is typically just overnight. For these reasons, the preeminent role of surgeon volume in the outcome of this procedure has strong intuitive validity. In the case of lung resection, in contrast, patients rarely die because of direct technical complications of the procedure itself (e.g., bleeding or leakage from a bronchial stump); they die from cardiac events, pneumonia, and respiratory failure. Hospital-based services (e.g., intensive care, pain management, respiratory care, and nursing care) are very important, and the average length of stay is relatively long. Thus, it is not surprising that hospital volume was more important than surgeon volume in determining the outcome of this procedure. Of course, these two procedures represent the extremes. As suggested by our analysis, factors related to both surgeon volume and hospital volume seem to be important for most high-risk procedures

So if you're going to have an endarterectomy done, your best bet is to go with the experienced surgeon, while with a lung resection you do better with a high-volume hospital.
With a pancreatic resection outcomes are equally affected by surgeon and hospital volume. Of the eight procedures listed the members of the Acme Surgical Corp only do two, endarterectomy and AAA repair. Our vascular trained surgeon falls into the "middle volume" of both (18-40 CEA/year and 8-17.5 AAA/year).
I think that the "spread" between low and high-volume surgeons would be higher if complications (esp strokes after CEA) were measured in this study, rather than just mortality. The vascular literature has good studies showing that the stroke rate is lower with experience, regardless of specialization.
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