Anthem Blue Cross and Blue Shield, Virginia's largest private insurer, is rolling out a new policy that would leave the state's hospitals to pay the bill for certain preventable surgical errors. While its no-pay list is not as expansive as the one set by Medicare to take effect this fall, Anthem will hold back payment for four core surgical mishaps: operating on the wrong body part; performing the wrong procedure on a patient; leaving medical supplies inside a patient; and operating on the wrong patient.