More than 75,000 Kaiser Permanente workers, including 23,000 in Southern California, are poised to launch the biggest healthcare worker strike in U.S. history beginning Wednesday, Oct. 4 if the two sides fail to reach a labor agreement.

The Coalition of Kaiser Permanente Unions and the healthcare giant have until 6 a.m. Wednesday to forge an 11th-hour contract before a three-day walkout begins.

The contracts for thousands of employees ranging from nurses to ER techs, respiratory therapists, dietary workers and home health aides expired Saturday, Sept. 30. A walkout will affect scores of Kaiser hospitals and facilities in California, including 23 facilities in Southern California, in addition to Colorado, Oregon and southwest Washington.

Also see: What to know if you’re a Kaiser member

Kaiser, which serves 9.4 million members in California, said it will keep all hospitals and emergency departments open. It operates three dozen hospitals and more than 500 medical offices in the state.

“Our facilities will continue to be staffed by our physicians, trained and experienced managers, and staff,” Kaiser said, adding that it could bring on “professionals contracted to serve in critical care roles specifically for the duration of a strike.”

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Replacement workers began filtering into San Diego-area hotels this week. Kaiser employees told the San Diego Union-Tribune that the healthcare provider ordered a temporary workforce of about 10,000. Kaiser has 60,000 union employees in the state.

In an email to members, the healthcare provider acknowledged it may need to reschedule some non-urgent appointments and procedures.

“We’ll contact you in advance if your appointment needs to be rescheduled,” Kaiser wrote. “It’s possible that you could experience longer wait and hold times during a strike. We apologize for any inconvenience and appreciate your patience.”

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The key sticking points in the negotiations have been staffing and wages with the coalition seeking a 25% raise over four years and a $25-per-hour minimum wage for all workers across the U.S. Kaiser in earlier negotiations offered 13%-16% raises over four years depending on the state and a $23 minimum wage for California workers.

The coalition also alleges Kaiser is behind unfair labor practices and unsafe staffing levels, all of which have undermined patient care.

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“I see my patients’ frustrations when I have to rush them and hurry on to my next patient,” said Jessica Cruz, a licensed vocational nurse at Kaiser Los Angeles Medical Center. “We’re burning ourselves out trying to do the jobs of two or three people, and our patients suffer.”

Employees are prepared to picket hospitals and other facilities in Los Angeles, Anaheim, Baldwin Park, Moreno Valley, Antelope Valley and the South Bay, among other Southern California locations.

Angelica Mateo, a Kaiser licensed vocational nurse in Pasadena, said she’s ready to walk out.

“Everyone is pumped up,” the 37-year-old West Covina resident said. “No one wants to go on strike, but if this is the only way we can make Kaiser executives listen to us, we’ll do what we have to do. Our coalition represents a third of Kaiser’s workforce, so even a three-day strike will make a huge impact.”

In a statement issued Monday, Kaiser said its goal is to reach a “fair and equitable agreement” that strengthens Kaiser as a “best place to work,” while ensuring affordable and easy-to-access quality patient care.

“A strike is not inevitable, and it is certainly not justified,” management said.

Kaiser acknowledged things are tough in the healthcare industry.

“Healthcare is still under great stress,” the company said. “More than 5 million people have left their health care jobs and burnout is at record highs.”

Employees say they’re grappling with skeletal staffing.

In a recent “Crisis in Care” survey of 33,000 Kaiser employees by SEIU-United Healthcare Workers West, two-thirds said they’d seen care delayed or denied due to short staffing.

“We need to keep working together to get through this because the reality is that we are still in a health care crisis in this country,” Kaiser said. “Access to care is stretched thin and it will take time to recover as an industry and stabilize the US health care system.”

Kaiser isn’t the only healthcare business facing a strike.

Nurses and other medical personnel at St. Francis Medical Center in Lynwood plan to strike the week of Monday, Oct. 9 because of severe understaffing, and employees at four Southern California nursing homes who claim they’re chronically understaffed have authorized their bargaining team to call a strike if conditions don’t improve.

Staff writers Ethan Baron and Paul Sisson and CalMatters contributed to this report.