The Irish Patients' Association, which lobbies to improve patient care, said no major crises were reported yesterday, and nurses had responded well to emergencies.
Its spokesman, Mr Stephen McMahon, said he was worried about the physical toll of the strike on hospital doctors and consultants if it continued into its third day tomorrow. Hospital doctors and consultants are to carry out many of the tasks normally done by nurses, such as administering injections and intravenous drips.
Mr McMahon said he was also concerned that the families of patients would find it difficult to get through to hospital wards by telephone at night.
He advised patients who are not sure whether their procedures or appointments will be affected to contact their hospitals.
The Irish Cancer Society's chief executive, Mr Barry Dempsey, said he was concerned about how the situation would develop, "but at this point we haven't yet seen the reality of how it will work out".
Mr Dempsey said rescheduling appointments of cancer patients was not suitable as they were vulnerable and in need of support following diagnosis. "As new patients are referred to limited services, the backlog will start accumulating and it will take weeks to bring services back on stream once the strike is over," he said.
Anyone concerned about treatment can contact that Irish Cancer Society's help-line on 1800 200 700.
The National Association for the Mentally Handicapped of Ireland said the service for people in respite or day-care was affected, and varied from area to area. Many parents with children or adult relatives in day-care services staffed by nurses have had to look after them at home.
The association's assistant general secretary, Ms Deirdre Carroll, said nurses had done their best to avoid disruption, and there was "no huge sense of panic".
Ms Carroll said she expected that more people in day-care currently looked after by registered mental handicap nurses would be sent home in the coming weeks.
"While I'm sure people will manage to do what they can in the short term, in the long term it will get quite stressful and we would urge both parties to work to resolve the dispute," she said.
The Federation of Voluntary Bodies Providing Services to People with Mental Handicap said the strike cover agreed locally was satisfactory yesterday.
Its chief executive, Mr Brian O'Donnell, said families who have had to take over day-care of mentally handicapped relatives were under pressure. He said people in residential care were not being sent home unless there was adequate family support.