Taking a (By)pass on Surgical Volume

Turn up the volume, right? For years, experts have believed that in general the more often a hospital does a procedure, the better the outcome. For some procedures, specific cut points have become accepted—a recommended minimum of 500 a year for coronary artery bypass surgery, for instance. Now comes a study in this week's Archives of Surgery claiming that over the years, lower-volume hospitals have gotten to be just about as good at heart bypass surgery as the big bypass factories.

The researchers looked at a large sample of the 1.1 million bypass surgeries performed between 1988 and 2003. They found that by the end of the period, differences in death rates at high-volume behemoths that perform 500 or more bypasses per year, at somewhat less busy hospitals that do from 250 to 500, and at the lesser lights that perform 249 or fewer were trivial. Death rates at the low-volume centers, in fact, had declined more sharply than at hospitals in the two higher-volume groups—from 5.9 percent to 3.5 percent.

The researchers call their results "counterintuitive," and have no explanation other than a trickle-down of surgical skills and advanced practices, and perhaps hospitals that no longer do the volume of bypasses they used to but still maintain high standards of care.

I wish they'd looked at individual surgeon volume. The number of bypass patients dropped by about one sixth from a peak of about 87,000 in 1997 to 73,000 in 2003 as more patients opted for stenting instead. (By 2003, the number of stent cases hit almost 170,000.) Many heart surgeons retired or turned to other areas. A one sixth decline in the number of surgeries isn't all that much. How about the possibility that fewer surgeons are divvying up the somewhat smaller number so that many surgeons even at lower-volume hospitals do a substantial number? I'd argue that in the end it's the individual surgeon, not the hospital, wielding the cutting tool. But this study did not examine that possibility.