The Health Service Executive (HSE) is warning of significant disruption to health services on Thursday.
Striking by 37,000 nurses and midwives is due to end at 8.00am, but patients are being warned of knock-on delays following Wednesday's action.
Some 25,000 medical appointments were cancelled, and the HSE has said it will contact those affected to re-schedule within the next two to three weeks.
INMO members have taken to the picket lines outside hospitals and HSE facilities, demanding pay increases and Government action on staff shortages.
The strike will last for 24 hours, with another two strike dates scheduled for next week if the dispute continues.
Pictured nurses from the INMO trade union on the picket line outside Beaumount Hospital in Dublin | Image: Sam Boal/RollingNews.ie
The Government has warned that wage hikes for nurses would open the floodgates for other unions to seek pay claims, which the State cannot afford.
The HSE national director of acute operations, Liam Woods, said emergency departments will be under pressure.
"I think tomorrow will be quite busy: we're seeing a slight reduction in attendances at emergency departments today - so we would anticipate that we will see an increase tomorrow.
"We'll also be watching the impact, if any, of the weather that is forecast overnight and indeed into tomorrow.
"But we would anticipate given that the emergency departments have been quieter today as a result of the industrial action they will be busier tomorrow, and that'll bring its own pressures".
Earlier, Health Minister Simon Harris said there was no consequence-free way to give nurses a pay rise.
"What I will say to patients is there's a willingness on the side of Government and management to find a resolution.
"But we have to operate within that space of not breaching the Public Service Stablility Agreement.
"To do anything else would be grossly irresponsible - there is no consequence-free direct pay rise."
INMO nurses arriving at the picket line at Connolly Hospital to chants of “what do we want? Safe staffing! When do we want it? Now!” pic.twitter.com/6cnPES3GTz
— Shane Beatty (@ShaneBeattyNews) January 30, 2019
Nurses outside Connolly Hospital in Blanchardstown, Dublin told Newstalk why they are picketing.
"We have to do it," one said. "Enough is enough."
"it is time that we got out safe commission, our safe pay and patients and nurses are treated with respect - they are given fair care and we get the value and appreciation that nurses deserve."
Another said nurses need to "stand up for our patients; we need to stand up for our staff."
"This is for the future of nursing and the future of everybody out there - all the public support, we do appreciate it - who knows? These people may need healthcare in the future.
"We need to do it and we need to do it now."
The beeping from passing drivers keeps coming for the striking nurses at Connolly Hospital pic.twitter.com/dhUaM6oZHa
— Shane Beatty (@ShaneBeattyNews) January 30, 2019
One nurse on the picket line at Mayo University Hospital in Castlebar said that nurses do not vote 95% in favour of strike action unless they feel they have "reached the end of the line".
"They can see what's happening to the health service, and it's time for the Government to listen to the nurses," he added.
Recruitment and retention
The dispute is centred on pay issues and working conditions within Irish hospitals – which unions have warned are causing the recruitment and retention crisis in the health service.
Nurses are demanding pay increases of about 12% - and for the HSE to take steps to deal with recruitment and retention issues.
The Government has insisted it will not do a special deal for health workers – and said any pay increase would open the floodgates for other public service unions to seek the same.
Trainee Midwifes at University Maternity Hospital Limerick
"No option"
Fianna Fáil health spokesperson Stephen Donnelly said staff shortages in hospitals mean nurses have been left with little option but to strike.
"No nurse of midwife wants this strike but they feel they have been left with no option," he said.
"I have been talking with nurses around Ireland and they are at their wits end.
"They are trying to provide professional care but without the needed supports.
"The Government needs to listen to what they are saying and engage meaningfully with them."
You can find out what services are running here.
The strike went ahead after the Labour Court said it could not intervene in the dispute.
It remains up to the INMO and the HSE to resolve it – with further strike days planned for next month.
Reporting from Shane Beatty and Jack Quann
