All complex surgery is being moved away from Portlaoise Hospital, and emergency department hours are being reduced to a daytime-only service.
Complex surgeries are being transferred to St James's Hospital in Dublin or to the Midlands Regional Hospital in Tullamore.
It follows a damning report into Portlaoise Hospital by the health watchdog, HIQA.
In a statement, the HSE said that the volumes of complex surgeries at Portlaoise are too low to maintain the required expertise of clinical staff.
"Complex surgery in MRHP will be transferred to St James's Hospital or Tullamore as the volumes are too low to maintain the requisite expertise of clinical staff," the statement says.
"This will result in the discontinuation of undifferentiated surgical cases that present at MRHP Emergency Department. There is a progressive complex planning process (with a lot of interdependencies) for surgery that will in the medium to longer-term will result in a reduction of ED opening hours (overnight)".
It adds that this planning process will be done with the engagement and input of relevant staff.
Susan O'Reilly is Chief executive of the Dublin Midlands Hospital Group, which covers Portlaoise. She told Jonathan Healy on Newstalk Lunchtime what exactly has been changed:
