WESTWOOD (CBSLA.com) — Some University of California hospital workers will participate in a union strike on Wednesday.

The American Federation of State, County and Municipal Employees Local 3299, the union representing 22,000 patient care and service employees, is calling for the one-day walkout at hospitals in San Francisco, San Diego, Davis, Irvine and Los Angeles.

READ MORE: Man Shot While Walking Dogs In Hollywood, 2 French Bulldogs Stolen

For the past year, employees have been fighting over staffing issues and changes to their pension.

Locally, the UCLA and UC Irvine medical centers will remain open, but have canceled many elective surgeries.

READ MORE: 2 People Killed, 3 Critically Hurt In Violent South LA Collision

Hundreds of replacement workers will fill in for workers on strike.

Dr. Tom Rosenthal, the chief medical officer for the UCLA Hospital System, issued a statement, which said, “We sincerely apologize for any inconvenience this strike may cause our patients and their families and friends. However, every effort is being made to ensure that the hospitals and clinics that are part of the UCLA Health System remain open and continue to deliver the highest level of patient care.”

MORE NEWS: At Least 2 Homes Destroyed When Wind-Whipped Fire Rips Through Bloomington Neighborhood

Patient care facilities in the UCLA Hospital System that could be affected include Ronald Reagan UCLA Medical Center; UCLA Medical Center, Santa Monica; UCLA’s Resnick Neuropsychiatric Hospital; the David Geffen School of Medicine at UCLA; Mattel Children’s Hospital UCLA; and community and outpatient clinics.