The planned strike by nurses at seven hospitals over understaffing and overcrowding on Thursday has been deferred.
The INMO Executive Council reached an unanimous decision to accept a set of proposals agreed with the Health Service Executive overnight.
The breakthrough came after 19 hours of negotiations at the Workplace Relations Commission.
The aim was to provide sufficient assurances to nurses that measures agreed before Christmas to address overcrowding and understaffing would actually be implemented.
The revised proposals include a number of "confidence-building" provisions and clarifications.
The procedures for early identification of the risk of overcrowding, and of the operation of crisis protocols known as escalation policies, have been clarified.
There will be mandatory weekly high level meetings at hospital or group level between the CEO, Chief Operations Officer Clinical Director and Director of Nursing and the nurses representatives to monitor implementation of the new arrangements.
There has also been clarification of how the roles of posts of additional responsibility and promotions will function in emergency departments.
Minister for Health Leo Varadkar has welcomed the decision to defer the strike action, saying he understands the INMO will be recommending that emergency department nurses accept them in a ballot.
INMO General Secretary Liam Doran has stressed the dispute was not about money, but was about securing patient safety.
HSE National Director of Human Resources Rosarii Mannion had said she hoped the clarified proposals would increase confidence among local staff that they would see active engagement of senior management in implementing them.
She said there would now be a consistent policy on escalation when overcrowding was serious which would be applied locally in each hospital, and would be overseen through a group forum.
She said that there had been absolutely no changes to the monetary incentives for the recruitment of nurses.
WRC Director General Kieran Mulvey, who co-chaired the talks, said the original proposals to address overcrowding and understaffing had been strengthened by creating structures in which they can be monitored reviewed and evaluated.
He said that in addition, the parties would be returning to the WRC in a month to assess progress on implementation.
He said the important issues were patient safety and the integrity of the professionalism of nurses, but he believed that the final document delivered the level of assurance the nurses had been seeking.