As many as 4,800 nurses are scheduled to set up picket lines Sunday at five Allina Health hospitals in an unusual seven-day strike that seeks to thread the needle between maximizing the pressure on hospital management and minimizing the disruption to patients.

Nurses are expected to walk out at the end of their overnight shifts at 7 a.m. and be replaced by 1,400 temporary nurses from around the country hired by Allina through staffing agencies.

The affected hospitals are Abbott Northwestern in Minneapolis, United in St. Paul, Mercy in Coon Rapids and Unity in Fridley, along with the Phillips Eye Institute in Minneapolis, which is also part of the Allina system.

On Saturday, a couple of hundred nurses met at the Minnesota Nurses Association office in St. Paul to make signs for the protest, one of several signmaking events held throughout the week.

Leaving patients was a tough choice, said MNA spokesman Rick Fuentes, but one that nurses felt necessary in the face of Allina's demand that they surrender their union-protected health benefits.

"All nurses have compassionate ties toward the patients they're taking care of," he said. "This is a difficult decision."

Months of negotiations failed to produce a new three-year contract, as Allina insisted that union nurses transition to its corporate health plans — which provide more financial incentives to use efficient forms of care, such as urgent care clinics instead of emergency rooms. Allina projects annual savings of $10 million from the switch.

Whether a seven-day walkout will sting Allina enough to change its stance is unclear. Most strikes historically have been open-ended battles that dragged on until the parties compromised, or ceremonial demonstrations that lasted one day.

The last Twin Cities nursing strike, in June 2010, involved 14 hospitals and 12,000 nurses, but lasted only one day.

"I'm not going to say it's never been done," said John Budd, an industrial relations professor at the University of Minnesota, about a one-week strike. "But I do think this is sort of the next step of this experimentation [in job actions]. Given how steadfast Allina seems to be, [the union] must have decided that one day wasn't going to be enough to put pressure on them."

Research on the impact of U.S. nursing strikes is thin. Assessing whether nurses have distinct leverage compared to other union workers is difficult, Budd said, because it is difficult to declare winners and losers at the end of any negotiations.

In 2010, for example, some felt the Twin Cities nurses lost because they surrendered a key demand for fixed patient-nurse ratios to ensure adequate hospital staffing. On the other hand, they protected other contract provisions about nurse staffing and safety, and preserved pensions and other benefits as well, said Bernadine Engeldorf, a union vice president and nurse who participated in the MNA's 38-day strike over seniority rules in 1984.

"You always lose in a strike, somewhat, I guess," she said. "Financially, you don't make up the time you don't work. But if you maintain your ability to have a voice in the workplace, that is very important."

There is little question that nursing strikes exert a financial impact. Allina's audited financial statement for 2010 showed that it spent more than $14 million to replace its nurses for the one-day strike in June and to prepare for the potential of a longer strike that had been scheduled for July.

And at least one study suggests that patient care suffers. The National Bureau of Economic Research in 2010 published an analysis of hospitals in New York between 1984 and 2004 and found deaths and readmissions occurred more often in hospitals during strikes — regardless of whether the hospitals tried to reduce services or hire replacement nurses.

The potential impact on patients has raised questions as to whether nurses should even be allowed to strike — one reason that federal labor law requires nursing unions to provide their employers a 10-day notice.

St. Cloud State University philosophy Prof. Paul Neiman examined the issue in 2012 and concluded that nurses have an ethical right to strike in the American market-based system, where the financial interests of insurers, doctors, nurses and hospitals compete with one another.

"As one member reduces its contribution (to patient care), other members must increase their contribution in order to meet the community's obligation to provide health care," Neiman wrote. "Denying nurses the right to strike enables the others to place the burden of the community's responsibility on a single group, and leaves them powerless to seek a remedy."

Allina officials weren't surprised when the union called for a strike; the health system had been planning for that possibility for months and recruiting replacements since early May. They expressed disappointment, though, with a walkout over health benefits that already serve thousands of other Allina employees.

"This is not a situation we wish to find ourselves in," said Christine Moore, Allina's vice president for human resources. "Our complete focus now is on ensuring safe and quality care for our communities."

Whether Allina will lose business during the strike is unclear. Hospital officials said they're prepared to maintain current levels of surgeries and other services at Abbott, United and Mercy. On the other hand, they also acknowledged in a document released Friday that a decline in patients might prevent them from bringing all the nurses back immediately after the strike.

In past years, Allina negotiated its nursing contract concurrently with the Fairview, HealthEast and Children's hospital systems. This year, the other Twin Cities systems agreed to leave benefits unchanged and only negotiate wages with their nurses.

While negotiating leverage might seem greater when nurses from all the hospital systems strike at once, the U's Budd said a focused strike can be more effective and preserve the union's resources.

However, both sides can argue that the other is being unreasonable, he noted. The union can argue that other health systems maintained the benefits that Allina wants to discontinue. But Allina can argue that thousands of other employees, including executives, are satisfied with the health care through the company plans.

Staff writers Christopher Snowbeck and Kavita Kumar contributed to this report. Jeremy Olson • 612-673-7744