The Irish Nurses and Midwives Organisation has described the rise in the number of patients presenting at hospital emergency departments as "unprecedented".
The Health Service said there had been a 10% increase in patients nationally, and there were 386 patients on trolleys this morning.
The biggest rise is at Our Lady of Lourdes Hospital in Drogheda - up 21% - followed by the Connolly Hospital in Blanchardstown and Cork University Hospital, both up 14%.
General secretary of the Irish Nurses and Midwives Organisation Liam Doran said: "It's correct to say the (emergency) departments have been under unprecedented pressure.
"The escalation measures we've agreed involve a system-wide response and the cancellation of elective procedure sis a manifestation that the policy is beginning to work."
Health Minister Leo Varadkar said yesterday that everything that can be done is being done to tackle the overcrowding.
“Part of that escalation protocol is that we cancel non-urgent elective surgeries when there is overcrowding, so that is an example of the escalation framework working,” he said.
“It’s not ideal, but it’s better than having very large numbers or even higher numbers on trolleys."
And as the flu season has yet to peak, there are fears the number of people attending hospital may rise further.