Amid growing fears that the United States could face a shortage of ventilators for coronavirus patients, state officials and hospitals are quietly preparing to make excruciating decisions about how they would ration lifesaving care.

The plans may not be necessary, as officials are scrambling to secure more ventilators, which can make the difference between life and death for coronavirus patients in critical condition who are struggling to breathe. Social distancing and other mitigation efforts to slow the virus' spread could prevent hospitals from being overwhelmed. But hospitals are already huddling with state health officials to hammer out their policies to determine which coronavirus patients would get ventilators if they run short — essentially deciding whose lives to save first.

In Maryland, state officials are in discussions with the biggest hospital systems in the region about how to factor in age, pre-existing health conditions, overall life expectancy and other criteria to determine which patients would have priority if there are not enough ventilators, said Dr. David Marcozzi, who is directing the coronavirus response for the University of Maryland Medical System, which has 13 hospitals.

"These are conversations that no one wants to have. But we need to have these conversations just in case," said Marcozzi, who has been appointed to the state's coronavirus response team. "We need to put steps in place to ensure the public's confidence that those difficult decisions will be made with the greatest care."

States are revisiting recommendations that many began developing in the aftermath of Hurricane Katrina 15 years ago, when medical providers hastened the deaths of some patients after their hospital lost power. The goal is to provide hospitals with consistent, transparent guidance for patient care when lifesaving resources are scarce — part of a framework known as "crisis standards of care," which prioritize the survival of the group over the survival of the individual patient during disasters.

"You're looking for the most good for the greatest number — it really is a shift," said Dr. Stephen Cantrill, an emergency physician at Denver Health Medical Center, who helped create foundational recommendations for the standards from the National Academy of Medicine. "Normally, we operate with the individual patient's best interest at heart."

In Italy, the flood of coronavirus patients in critical condition has already forced hospitals to make decisions to prioritize care for younger, healthier people who have better chances of survival. U.S. officials and health care providers are now racing to prevent hospitals from having to face such wrenching choices, pleading with the White House to help procure more ventilators and with the public to stay at home and avoid emergency room visits whenever possible to prevent hospitals from running out of intensive care bed space, equipment and other scarce resources.

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In the meantime, state officials and major hospitals across the country are making sure they are prepared for the worst. While most of the state plans have been years in the making — often created in consultation with bioethicists, legal experts and religious leaders — they have never been broadly put into effect.

"Without question, this is certainly the closest we've come on a nationwide level," Cantrill said.

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Some hospitals are already resorting to outdoor triage tents and other contingency measures to handle the influx of patients. And many are working out their own plans to alter care should they run out of ICU beds, trained staff and ventilators. In New York — which has more cases than any other state and a potential shortfall of 18,000 ventilators — Montefiore Health System is revamping its ventilator allocation policy and determining which staff members will serve on the triage team that would make those decisions, said Dr. Patricia Powell, director of the Montefiore Einstein Center for Bioethics.

If there isn’t enough equipment, "you might not get access to a ventilator if you get a prognosis that no matter what, you probably won't get better," said Powell, who served on a New York state task force that created guidelines for hospitals on which patients to ventilate if there is a shortfall. "That's not a circumstance that people in America are used to thinking about."

In Washington state, where more than 50 people have died so far, state officials are conferring with hospitals, outside experts and the Centers for Disease Control and Prevention on revised guidelines to allocate scarce resources like ventilators, according to Dr. John Hick, a disaster response expert who is helping to review the state's plan.

"Our supply situation is very serious," said Cassie Sauer, CEO of the Washington State Hospital Association, which represents hospitals across the state. "Expect a surge plan and a crisis standards plan to be public shortly."

Thirty-six states have worked on plans for rationing care during emergencies since Hurricane Katrina, but not all of them have been made public, said Hick, a Minnesota-based physician who helped develop national guidance for states and hospitals to follow. The state guidelines go into effect only if state officials decide to enact them during a public health emergency, which has yet to happen with the coronavirus. The recommendations, which are nonbinding, can vary significantly from state to state.

Minnesota's recently updated guidance includes contingency measures to make the most of a dwindling supply of ventilators, such as decreasing elective procedures that require ventilators, reusing certain ventilator parts or employing alternative forms of respiratory support.

Minnesota's patient care guidelines also include a detailed breakdown of the factors used to determine whether a ventilator will be withheld or removed from patients, including their response to the treatment, likelihood of death and underlying conditions, such as severe chronic lung disease, congestive heart failure and cirrhosis. The state also details strategies for palliative care to relieve pain, explaining that "it may be the only care that is able to be provided due to the patient's prognosis and available resources."

New York's ventilator guidance does not specify the medical conditions that would exclude patients from being ventilated. Instead, it recommends that hospitals create a list of such conditions based on “immediate or near-immediate mortality even with aggressive therapy”; rate patients based on their likelihood of survival; and use trials to determine how much they are medically benefiting from a ventilator.

Age should be used only as a tiebreaker, the New York state panel said, and health care workers and first responders should not get priority over others. By contrast, Michigan's guidelines specify that hospitals could choose to prioritize workers performing "essential social functions" — including doctors and nurses treating patients, as well as police, military members and firefighters — to receive scarce resources like ventilators and ICU beds.

Disaster planning experts stress that it is crucial to create such guidance ahead of time — and to separate the decision-making process from the doctors on the front lines of caregiving.

"Without prior planning, you're going to have these life-or-death decisions made by clinical staff not trained in this, who are exhausted and overworked," Powell said.

Disaster response experts stress that there is still time for the public and officials to act to avoid forcing hospitals to make such painful choices.

"It all depends on how effective our social controls are — how much can we flatten the curve?" Hick said, referring to the social distancing measures the public can take to slow the virus. "Some cities are on their way to crisis. We're holding our breath."

CORRECTION (March 19, 2020, 11:26 a.m. ET): An earlier version of this article misstated the number of hospitals in the University of Maryland Medical System. There are 13, not 14.