In meetings and conferences where the presenter asks anesthesiologists and pain physicians whether they are participating in—or negotiating with—an Accountable Care Organization (ACO), very few, if any, of the doctors raise their hands.  Everyone is aware of the concept of ACOs, but almost no one has any experience with them yet.  Nevertheless, there are significant ACO developments across the country.Tens of millions of patients are already receiving medical services through ACOs. A year ago—even before the United States Supreme Court’s decision upholding most of the Affordable Care Act—32 ACOs were participating in the Medicare Pioneer demonstration program  and 27 more had signed up to become Medicare ACOs.  Becker’s Hospital Review briefly described 80 Accountable Care Organizations to Know, both commercial and Medicare, in an online article dated April 16, 2012.  Many of these ACOs were formed by hospitals and health systems in partnership with health plans.  They range in size from as...