Congress is tangling with doctors, hospitals and seniors organizations as it seeks to push through a long-sought change to Medicare that carries a $150 billion price tag. Doctors cheered this month when committees in the House and Senate released a framework for a permanent "doc fix" that would repeal a flawed payment formula under Medicare that Congress has routinely patched since the late 1990s. But excitement about the breakthrough on the Medicare Sustainable Growth Rate (SGR) was tempered by the fact that lawmakers left the most difficult question unanswered: how to cover the $150 billion cost.