A planned five-day strike by thousands of registered nurses and other Kaiser Permanente health care workers in California, Hawaii and Oregon ended on Sunday, union leaders and the health care system said. California-based Kaiser Permanente said it welcomed back about 30,000 employees who participated in the strike, which began Tuesday and ended Sunday morning. The United Nurses Associations of California/Union of Health Care Professionals, which represents registered nurses, pharmacists, nurse midwives and other health care professionals in California and Hawaii, said in a statement that more than 500 hospitals and clinics were impacted by the strike.