Long-feared rationing of medical care has become a reality in some parts of the United States as the delta variant drives a new wave of coronavirus cases, pushing hospitals to the brink.

Alaska and Idaho have activated statewide “crisis standards of care,” in which health systems can prioritize patients for scarce resources — based largely on their likelihood of survival — and even deny treatment. The decisions affect covid and non-covid patients. Some health care providers in Montana have turned to crisis standards as well, while Hawaii’s governor this month released health workers from liability if they have to ration care.

Some states have no crisis standards of care plans, while others just created them during the pandemic. The common goal: Give health-care workers last-resort guidance to make potentially wrenching decisions. But people disagree on the best calculus.

“We only end up needing crisis standards of care when our other systems have utterly failed,” said Emily Cleveland Manchanda, an assistant professor of emergency medicine at Boston University School of Medicine.