For more than a quarter century, registered nurses at Santa Rosa Memorial Hospital have worked in relative harmony with hospital administration.

Whenever labor negotiations heated up around a new contract, the local Staff Nurses Association often threatened to strike -- five times during the past six contract negotiations. But hospital management and the nurses union always seemed to work things out in the end.

That enduring atmosphere of collaboration ended Tuesday, when about 150 nurses picketed in front of Memorial Hospital in a bid to repel what they said were dozens of "take-aways" at a time when the nonprofit hospital is enjoying healthy financial returns. The nurse's union said the hospital's operating margin -- the difference between its revenue and costs -- was a record $38 million for the fiscal year ending June 30.

"They've never made that much money in the past," said Sue Gadbois, the union president. "In the past they've been able to offer competitive wages and benefits. Now all of a sudden, with record profit they're not able to do that. It doesn't add up."

Memorial administrators say their operating margins allow the hospital to invest in new technology at a time when it is under unprecedented pressure to keep costs under control. They anticipate continued reductions in government payments such as Medicare and Medi-Cal, accompanied by reductions in hospital payments under President Barack Obama's health care overhaul.

"We value our registered nurses. The care they provide to our patients is phenomenal. We also value and want to remain a vital part of this community," said Debra Miller, vice president of human resources for St. Joseph Health System in Sonoma County, which operates Memorial and Petaluma Valley hospitals.

"In order to do so -- just as every other employer is doing -- we need to make sure we are paying attention to the future," Miller said.

On Tuesday, nurses with the 660-member union began gathering in front of Memorial Hospital at about 4:30 a.m. By 9 a.m. the two-day strike was in full swing.

Carrying signs that proclaimed, "Profits to the Bedside," or "It's not about the money," the nurses rallied at the intersection of Montgomery Drive and Sotoyome Street as smaller groups of nurses walked up and down the street. Cars frequently honked their horns in support.

The hospital has proposed reducing the night differential, the extra amount paid for working the night shift, from 25 percent to 15 percent of regular pay.

Also, the hospital proposes reducing on-call pay from 50 percent to 30 percent of regular pay. Hospital officials said the reduction is similar to what Memorial employees represented by the National Union of Healthcare Workers accepted in May.

But the SNA said on-call duties for nurses are particularly grueling because Memorial is the region's only level II trauma center.

The union and St. Joseph have also locked horns on the wage increase. The hospital proposes a 1 percent increase beginning in 2013 and another 1 percent increase in 2014.

The union wants a 5 percent increase beginning this month and another 5 percent increase next year.

Gadbois, the union president, said that nurses' wages at Memorial are between 5 percent and 15 percent lower than they are at other Bay Area hospitals, including Kaiser Permanente Medical Center in Santa Rosa, Marin General and Dignity Health, formerly Catholic Healthcare West in San Francisco.

"We are trying to keep up with the market for nurses so that we can continue to retain and attract nurses," Gadbois said.

Miller said the average nurse at Memorial makes more than $100,000 a year, excluding benefits.

"We cannot continue to escalate our wages," she said.

During the strike, hospital officials said acute care would continue to be offered, but St. Joseph Health temporarily closed its urgent care centers in Rohnert Park and Windsor. These patients will be treated at its Santa Rosa urgent care facility at Sebastopol Road and Corporate Center Parkway. The Santa Rosa center will remain open from 7 a.m. to 7 p.m.

St. Joseph's three urgent care centers will reopen on Thursday morning, with striking nurses called back to staff the centers as needed.

St. Joseph contracted 150 replacement nurses to fill in for picketers during the two-day strike at the hospital. But hospital officials said the replacement nurses will work through the week because they had to be contracted for four days.

On June 13, striking nurses at Petaluma Valley Hospital -- the hospital's first strike in its 30-year history -- were essentially "locked out" for several days beyond their one-day strike.

In both cases, hospital officials said the strikes would not interrupt patient care and that replacement nurses were "highly qualified."

But nurses questioned whether the new nurses would be able to provide adequate care, given their limited training and the complexities of the hospital's computer systems.

You can reach Staff Writer Martin Espinoza at 521-5213 or martin.espinoza@pressdemocrat.com