The organisation was fined €10,000, plus €13,000 to cover legal fees.
The Health Service Executive (HSE) has pleaded guilty to failure to protect its staff from serious abuse and assault.
A number of nurses were assaulted by a patient in a now closed department of psychiatry in Our Lady's Hospital, Navan.
Peter Hughes, General Secretary of the Psychiatric Nurses Association, spoke about the incident on RTÉ Radio 1's
Morning Ireland on Thursday (28 April).
"The HSE pleaded guilty to four breaches of the Health and Safety Welfare Act," Hughes explained.
"It resulted in the assault of three nurses in August of 2016.
"However, this followed a letter of concern by our branch official only four months earlier regarding the increase in incidents of violence and presentation of more patients with challenging behaviour.
"They had a lot of physical bruises and injuries, however, the main effect was the psychological distress.
"They all got back to work, but it took some time for that to happen."
The HSE pleaded guilty to not having an emergency response team in place to respond to the activation of a personal alarm, not having a security guard in place, and no magnetic doors operated by a swipe card system.
"I think the main issue here is that patients with challenging behaviour are not suitably treated in an acute admission unit," Hughes said.
"It's not cleared for those type of clients, it's not a therapeutic environment for those types of clients and patients.
"The Government policy, Vision For Change 2006, recommended that there would be four 30-bedded rehabilitation units throughout the country.
"And now, 16 years on, none of those were progressed, none of those were built, and what we're seeing now is an increasing number of patients with challenging behaviour in acute admission units which are not suitable for the treatment and the therapeutic environment for those types of patients, which is putting staff and other patients at risk."
In a statement to JOE, the HSE said the following:
"The HSE accepts the ruling at Trim Circuit Court yesterday (Wednesday, 27 April) following prosecution by the Director of Public Prosecutions (at the suit of the Health & Safety Authority) regarding an incident in which three HSE employees were assaulted on August 29th 2016 in the former Department of Psychiatry, Navan prior to its closure.
"The HSE entered a plea of guilty in the case.
"The safety of staff is a priority for the HSE and we deeply regret this incident occurred resulting in injury to our staff.
"While the charges in the case were specifically related to the incident of August 29th 2016 in the now closed Navan Department of Psychiatry, the HSE is committed to use the learning from this case to contribute to the safe operation of current services.
"Changes to the built environment and to clinical practice related to the management of violence and aggression have been implemented and we continue to assess the requirement for further measures.
"The HSE will continue to engage with the Health & Safety Authority as we develop policy and systems to ensure safe workplaces for our staff."
