American health care seems headed for big changes in 2017. A Republican Congress and president have promised to take us down a very different path. But the details are far from clear.

Tremendous uncertainty lies ahead, and some of the changes being discussed could bring chaos.

While the Affordable Care Act has attracted most of the attention, it is only part of the story. Many other programs are up for discussion, and the effects on our care could be profound.

Here are a few proposed changes to look out for.

First, regarding the ACA. Republicans have been promising to repeal and replace the law since it was passed in 2010, and they finally have political clout to do so. But there is one problem. They have still not decided exactly what they will repeal or what they will replace it with.

Complete repeal of the ACA is impossible. It is embedded too deeply throughout our health care system. Republicans could close down the ACA's insurance exchanges, but they are just the tip of the iceberg. To list just a few of the effects of complete repeal, it would shut down the market for generic versions of expensive bioengineered drugs, re-open the doughnut hole for Medicare drug coverage, throw millions of young adults off their parents' health coverage, make medical student loans more difficult to obtain, and drastically increase the indigent care burden on hospitals.

And that's not even to mention throwing millions of patients off of Medicaid, leaving them without access to anything more than emergency care and leaving hospitals with millions of dollars in unpaid bills.

Republican proposals for replacement keep popping up like weeds, and they are just as varied. The latest idea is to repeal the law, or some yet-to-be determined parts of it, and devise a replacement later on.

The problem is, the resulting uncertainty would make it difficult or impossible for hospitals, doctors, and insurance companies to plan ahead and could lead the entire system into chaos. Do the party's leaders in Congress care? We will see.

Beyond the ACA, Republican leaders in Congress, as well as Tom Price, Donald J. Trump's selection to head the Department of Health and Human Services, want to drastically change Medicare from a government-run system into a voucher program. Beneficiaries would use the vouchers to purchase coverage from private managed care plans.

But private plans have historically been more inefficient and expensive than traditional Medicare. Unless Republicans want to ignite a greater cost spiral, they will have to ratchet down the value of the vouchers. Will the vouchers then be worth enough to enable beneficiaries to purchase meaningful coverage? We don't know.

Changes have already been enacted to the Food and Drug Administration's approval process for drugs and devices as part of the 21st Century Cures Act that Congress passed in December. That law will speed up the FDA process by adding shortcuts. These may enable manufacturers to bring lifesaving products to market faster, but they may also make it easier for ineffective and dangerous drugs and devices to slip through. Should patients be hopeful or concerned? We will have to wait and see.

We should also pay close attention to public health. It is what protects us from global epidemics like Ebola and Zika and what keeps our food and drinking water safe. Some Congressional Republicans are calling for cuts in funding for these and similar efforts. Is the next epidemic or food-borne disease outbreak waiting to take advantage? Time will tell.

New directions can bring improvements, but uncertainty in a system as complex as health care can be devastating. Proposed changes could shake many of the pillars on which our health care rests and produce chaos. We should pay close attention as the new health care agenda unfolds.

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