With debate underway in the Senate over a bill to repeal and replace the Affordable Care Act (ACA), multiple amendments being considered, and no clear sense of what may or may not reach President Trump’s desk, U.S. lawmakers are perilously close to opening Pandora’s Box.

That risk goes far beyond changing the ACA. In the bills that emerged from the House and Senate, the most potent changes were to the size and nature of Medicaid—a formerly sacrosanct health care safety net that has been in place since 1965.

The changes proposed would affect a large and highly vulnerable population: poor children, people with disabilities, elderly people whose resources have been depleted, and adults suffering from short-term or long-term poverty. Yet, the House and Senate bills contain no direction on how to implement the proposed changes in a way that would not hurt the millions of people the program serves or the many others touched by the program. These high-stakes effects would be left to states and providers to remedy and for these populations to absorb.