We have been struggling in this country with the issue of rationing medical care for as long as I can remember. First it was restrictions on what traditional medical insurance would pay for. This was quickly eroded by lawsuits against insurance carriers. Then it was the gatekeeper concept for a while, and that was also eroded by patient dissatisfaction and by lawsuits. Restricting access to specialists, restricted formularies, etc. didn't work. And now we are pretty much back to the status quo ante, except that even more people can't afford medical insurance than ever before.
Having observed all of this my impression is that the only way to impose rationing is to do it across the board all at once, and the government will have to do it. The government is the only entity with enough power to make it stick. I don't think that we have the political will in this country to do that yet, and things will have to get much worse before we do.
This is not a perfect solution, of course, because the government will be susceptible to political pressure to inject nonsense and idiocy into the system. For example, there are categories of disease recognized by US government health entities that received recognition as real biological disease states only because the people who think they have those diseases, which are in fact most likely psychosomatic, have pressured the government into that position. Not because there is any actual evidence of an objective, biological abnormality.
The health care system of a certain Scandinavian country is at the verge of crisis over this sort of thing, in which a large proportion of the population is claiming disablity for having a disease that does not actually exist but that the system was politically forced to recognize.
We do have rationing in this country, make no mistake about it. And the rationing is of the form that poor people don't have access to the range of options and convenience of care that wealthier people do.
You might think that with medical insurance that you have access to the "best" care. It's not true. There are levels of care above you that you could only dream about, that only the very rich elites of this country can get. For example, if you need, say, a hemorrhoid removed you can use your company supplied insurance and go see a physician, get tests done 3 weeks later, surgery scheduled 6 weeks later, get kicked out of the hospital on the day of surgery and deal with any problems that arise between then and your next follow up visit yourself at home. If you can afford to forget the insurance you can fly somewhere and the whole thing will get done in 2 or 3 days, and nobody will rush you out of the door after surgery.
But don't worry, the care is more convienient and the doctors are more likely to humor you, but the rich are no healthier for it. Take a look at Michael Jackson's face if you doubt it.
Having been involved in the charity care end of the profession for many years I happen to think that the care provided by public hospitals is often the more rational because patients are generally not in a position to strong arm health care workers into providing unnecessary or extravagent care. Yet most of the time the care is quite adequate for the purpose of actually keeping people healthy, and because there is often more organization and more continuity those poor people generally get better care for chronic problems like hypertension and diabetes.