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High-risk surgeries are getting safer, but only partially because of more referral to high-volume centers, according to national data.

Operative deaths dropped significantly (P<0.001) for all high-risk procedures considered in a national Medicare database study by Jonathan F. Finks, MD, of the University of Michigan in Ann Arbor, and colleagues.

The relative decline from 1999 to 2008 ranged from 8% for carotid endarterectomy to 36% for abdominal aortic aneurysm (AAA) repair, the group reported in the June 2 issue of the New England Journal of Medicine.

"Although trends toward safer surgery are encouraging, tens of thousands of patients in the United States still die every year undergoing inpatient surgery," they wrote in the paper. "Wide variations in outcomes across hospitals suggest further opportunities for improvement."

Efforts in that regard to concentrate certain high-risk surgeries into the most experienced hands have had mixed results, which the researchers called not surprising.

Rising hospital volumes appeared to be driving the decrease in deaths for the high-risk operations with the strongest links between volume and outcome -- cancer resections. Higher hospital volume accounted for 67% of the decline in mortality for pancreatectomy, 37% of the mortality decline for cystectomy, and 32% of the mortality decline for esophagectomy.

One reason for the success may be that these procedures are "relatively uncommon; thus the financial penalty is minimized for smaller hospitals that refer patients to higher volume centers," the researchers noted in the paper.

But despite the push by payers and other organizations for minimum volume standards for a variety of other operations, high-risk cardiovascular operations were a different story.

For example, the number of hospitals performing coronary artery bypass grafting (CABG) rose, while the number of procedures done fell overall.

"This proliferation of hospitals may be related to both the financial incentives for hospitals to be involved in cardiac surgery and their need to provide backup for interventional cardiologists," the researchers suggested in NEJM.

And the biggest drop in operative mortality seen in the study was for abdominal aortic aneurysm (AAA) repair, which the researchers chalked up to more endovascular procedures in elective cases rather than greater concentration of procedures at high-volume centers.

In addition to more elective cases and referrals to high-volume centers, "the fact that mortality for all eight procedures declined during the 10-year study period suggests that there are factors common to all these procedures that contributed to mortality reduction," the authors noted. "Technological advances and the use of checklists in the operating room and improvements in perioperative care, particularly intensive care, have most likely enhanced operative safety."

So payers, policymakers, and professional organizations should reprioritize to target strategies that are most likely to reduce mortality across the board, Finks' group recommended.

"For most high-risk procedures," they wrote in the paper, "strategies such as operating room checklists, outcomes measurement and feedback programs, and collaborative quality improvement initiatives are likely to be more effective than volume-based referral."

The researchers examined national patterns through discharge data for the 3.2 million Medicare recipients ages 65 to 99 who had one of eight high-risk surgeries from 1999 through 2008.

The 30-day risk-adjusted mortality rates declined over this period as follows:

• 11% for resection of esophageal cancer (from 10.0% to 8.9%)
• 19% for resection of pancreatic cancer (from 7.3% to 5.9%)
• 16% for lung cancer resection (from 5.0% to 4.2%)
• 14% for resection of bladder cancer (from 4.3% to 3.7%)
• 13% for aortic valve replacement (from 7.6% to 6.6%)
• 21% for CABG (from 4.3% to 3.4%)
• 36% for AAA repair (from 4.4% to 2.8%)
• 8% for carotid endarterectomy (from 1.3% to 1.2%)

The researchers noted that their administrative data analysis could not rule out changing case mix as the cause of declining mortality, but suggested that was unlikely since predicted mortality rates remained relatively flat across the study period.

Another limitation was possibility of misclassification of hospital volume by using Medicare volume as a proxy, which would have underestimated market concentration.

Also, the results may not be broadly generalizable due to inclusion of only fee-for-service Medicare patients, Finks' group acknowledged.

"However, patients over 65 years of age account for more than half of all patients undergoing the operations we studied and an even larger proportion of perioperative deaths," they wrote in NEJM. "It seems unlikely that trends toward safer surgery would apply only to the elderly."

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