The cancellations are expected to be cancelled over the next two weeks as hospitals are told to look for extra ICU capacity.
Larger hospitals have been told to prioritise urgent treatment and Covid care as increasing cases put severe pressure on the system.
Just 17 adult ICU beds are available nationwide.
Intensive care consultant at the Mater Hospital, Dr Colman O'Loughlin, says there's serious concern about ICU capacity:
"We don't have the capacity to take any more than 300 predictable and beyond that, and that's including non COVID patients as well. And beyond that, who knows? It really is very difficult to project. We will try everything we can, but I can't give you any reliable predictions as what we can do. And that's why so concerning."
