Surgeon Caseload Largely Explains Hospital Volume Link to Mortality

Numerous reports have shown that operative mortality is lower at hospitals with high procedural volumes. Now, new research suggests that this association is largely mediated by the caseload of the operative surgeon.

Therefore, a patient undergoing surgery at a low-volume hospital by a high-volume surgeon could have a better outcome than one undergoing surgery at a high-volume hospital by a low-volume surgeon. The relative importance of surgeon volume depends on the particular procedure, according to the report published in the November 27th issue of The New England Journal of Medicine.

For example, mortality with aortic-valve surgery is almost entirely related to surgeon volume. So, in this case, selecting an experienced surgeon may be more important than choosing a high-volume hospital. In contrast, mortality with lung resection did not appear to be closely related to surgeon volume, so selecting a high-volume hospital may be more critical.

“Our findings are really surprising to me and to many who’ve followed this area carefully,” lead author Dr. John D. Birkmeyer told Reuters Health. ” For years, the assumption was that hospital volume mattered a lot more than the volume of the operating surgeon. Our study really didn’t find that to be true.”

“Many have assumed that high-volume hospitals have lower mortality because they have more perioperative resources to deal with complex cases,” Dr. Birkmeyer, from Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, noted. “Our study was the first that was comprehensive enough to tease out the contribution made to the association by the operative surgeon.”

The study involved an analysis of Medicare claims data for more than 470,000 patients who underwent one of eight procedures between 1998 and 1999. The operations included carotid endarterectomy, CABG, aortic-valve replacement, AAA repair, lung- cancer resection, bladder resection, esophagectomy, and pancreatectomy.

For each procedure, definitions of high and low hospital and surgeon volume were based on averages calculated from entire data set.

For most procedures, mortality was lower with a high- rather than a low-volume surgeon. However, the excess mortality related to surgeon volume varied widely by procedure type. For example, when a low-volume surgeon performed a pancreatectomy, a 3.61-fold increase in mortality risk was seen. The excess risk with lung resection, by contrast, was much lower – about 25%.

“For cardiovascular procedures, it was pretty clear that the volume of the operating surgeon was much more important in determining mortality than hospital volume,” Dr. Birkmeyer noted. “The findings were less clear for cancer operations–it seemed equally important to find a high-volume hospital as well as a high-volume surgeon.”

The new report is “important because it convincingly demonstrates that for many high-risk surgical procedures, there is a positive association between volume and outcome that is substantially related to the experience of the surgeon,” Dr. Kenneth W. Kizer, from the National Quality Forum in Washington, DC, notes in a related editorial.

“The report does not, however, shed light on what specific skills or characteristics of the surgeon or surgical team are related to lower mortality or on whether low-volume surgeons could improve their patients’ outcomes if they performed more procedures,” he adds.

N Engl J Med 2003;349:2117-2127,2159-2161.