Nursing unions are to assess the impact of a indefinite work to rule by 40,000 nurses and midwives tomorrow before deciding whether to escalate their action in the coming days.
Liam Doran, general secretary of the Irish Nurses Organisation told RTÉ News that an escalation was more likely to come in the next few days rather than weeks.
The industrial action, which started at 8am, is being taken by members of the Irish Nurses Organisation and the Psychiatric Nurses Association as part of their campaign for improved pay and conditions.
Mr Doran said the work-to-rule would be in place indefinitely until the dispute was resolved and that the action could escalate to nationwide work stoppages.
According to the HSE accident and emergency departments experienced backlogs, with outpatients in hospitals, community-based services, and psychiatric services also suffering service delays.
Brendan Mulligan, assistant chief executive with the Health Service Executive Employers Agency said tonight: "Today's disruption was not necessary and all of the issues associated with the unions' campaign have been subject to an in-depth examination by the Labour Court which recommended that their pay claims should be processed through the Public Service Benchmarking Body (PSBB)."
Under the work-to-rule, nurses will not answer telephones except in essential cases or carry out clerical, IT or administrative work. Nurses will record engagements with patients manually.
Unions, who are also threatening short work stoppages, said the action is indefinite and will continue until their demands for a 10 per cent pay increase and a 35-hour working week are met.
Ms Harney said it was "a great pity the nurses have taken this action" She discussed possible contingency plans with the Health Service Executive's Prof Brendan Drumm and chairman Liam Downey this evening. Mrs Harney appealed to the nurses to reconsider their action and to use industrial relations mechanisms to resolve the row.
"The people they're hurting is the people that they have chosen a career to help care for and that is patients. They are the only ones suffering in this dispute," she said.
"The people they're hurting is the people that they have chosen a career to help care for."
Ms Harney also said the true value of the nurses claims was not 10 per cent rise but a 32 per cent rise when social partnership, benchmarking and a cut in hours were taken into account.
She stressed that over the last number of years nurses in Ireland have seen their pay and conditions greatly improve, but added they could not be treated any differently than any other public servant.
Although both parties have agreed that nurses should work a 35-hour week, they could not agree on the timescale on when that could be achieved.
The HSE argues that a reduction from 39 hours will equate to 7.7 million hours being taken out of the system, with each individual nurse working 30 days less per year, and maintain it would be irresponsible to move forward without carrying out a risk assessment.
However, the INO argues its members have been working 30 more days than any other health care professional, despite a Labour Court recommendation 27 years ago for a 35-hour working week.
An incident room has been set up by the HSE to assess the situation in hospitals all over the country and respond to emergencies which may arise.
Angela Fitzgerald of the HSE said this evening that no elective surgery had been cancelled as a result of the dispute today, but that the situation would be "kept under review" tomorrow.