Surgeon specialization and operative mortality in United States: retrospective analysis

Abstract

Objective: To measure the association between a surgeon's degree of specialization in a specific procedure and patient mortality.

Design: Retrospective analysis of Medicare data.

Setting: US patients aged 66 or older enrolled in traditional fee for service Medicare.

Participants: 25 152 US surgeons who performed one of eight procedures (carotid endarterectomy, coronary artery bypass grafting, valve replacement, abdominal aortic aneurysm repair, lung resection, cystectomy, pancreatic resection, or esophagectomy) on 695 987 patients in 2008-13.

Main outcome measure: Relative risk reduction in risk adjusted and volume adjusted 30 day operative mortality between surgeons in the bottom quarter and top quarter of surgeon specialization (defined as the number of times the surgeon performed the specific procedure divided by his/her total operative volume across all procedures).

Results: For all four cardiovascular procedures and two out of four cancer resections, a surgeon's degree of specialization was a significant predictor of operative mortality independent of the number of times he or she performed that procedure: carotid endarterectomy (relative risk reduction between bottom and top quarter of surgeons 28%, 95% confidence interval 0% to 48%); coronary artery bypass grafting (15%, 4% to 25%); valve replacement (46%, 37% to 53%); abdominal aortic aneurysm repair (42%, 29% to 53%); lung resection (28%, 5% to 46%); and cystectomy (41%, 8% to 63%). In five procedures (carotid endarterectomy, valve replacement, lung resection, cystectomy, and esophagectomy), the relative risk reduction from surgeon specialization was greater than that from surgeon volume for that specific procedure. Furthermore, surgeon specialization accounted for 9% (coronary artery bypass grafting) to 100% (cystectomy) of the relative risk reduction otherwise attributable to volume in that specific procedure.

Conclusion: For several common procedures, surgeon specialization was an important predictor of operative mortality independent of volume in that specific procedure. When selecting a surgeon, patients, referring physicians, and administrators assigning operative workload may want to consider a surgeon's procedure specific volume as well as the degree to which a surgeon specializes in that procedure.

Fig 1 Risk adjusted and volume adjusted 30 day operative mortality rate by quarter of surgeon specialization. Mortality was defined as rate of death occurring within 30 days of initial hospital admission date. Surgeons were divided into four groups of equal size based on procedure specific volume and surgeon specialization. Procedure was defined as ICD-9 procedure code listed in principal procedure field. Procedure specific volume was defined as number of cases attributed to surgeon for specific procedure and total operative volume as all procedures attributed to surgeon. Surgeon specialization was defined as procedure specific volume divided by total operative volume across all procedures. Multilevel mixed logit regression was run, controlled for procedure specific volume; hospital where procedure was performed; age, sex, and race of patient; year of surgery; comorbidity profile; day of week; procedure type; days between admission and surgery; and whether hospital was academic medical center. P values were estimated to test for difference between bottom and top quarters within surgeon specialization. Average surgeon specialization for bottom/second/third/top quarter by procedure was: carotid endarterectomy 2.7%/7.3%/13.1%/26.4%; coronary artery bypass grafting 16.4%/27.9%/39.3%/56.3%; valve replacement 6.7%/13.9%/23.9%/50.4%; abdominal aortic aneurysm repair 0.9%/3.3%/6.9%/15.7%; lung resection 1.5%/4.5%/10.4%/41.0%; cystectomy 1.0%/2.2%/4.1%/23.0%; pancreatic resection 0.4%/1.4%/5.0%/28.9%; and esophagectomy 0.4%/1.1%/2.6%/10.1%