Hospital overcrowding last month was the worst on record, according to the Irish Nurses and Midwives Organisation.
The union said 9,679 patients were forced to wait on trolleys and chairs for admission to a hospital bed - an 11% increase on November 2017.
The INMO said that University Hospital Limerick had over 1,071 patients on trolleys waiting for admission to a hospital bed in November and it was the 18th month in a row that the hospital had the most overcrowding.
Five hospitals had more than 500 patients on trolleys last month.
Cork University Hospital had 932 patients on trolleys; University Hospital Galway had 676; there were 581 at Letterkenny University Hospital; 559 at Tallaght University Hospital and 549 at the Midland Regional Hospital, Tullamore.
The union said that much of the overcrowding is down to understaffing, which it claimed is caused by low pay levels.
INMO General Secretary Phil Ní Sheaghdha said 2018 is already the worst year on record for patients on trolleys.
She said that typically January and February are the worst months "so nurses and midwives will be looking to the New Year with a sense of dread".
She said overcrowding is no longer a winter problem, but a year-round problem.
"The health service needs more beds. Extra beds require extra nurses, but the HSE simply can’t hire enough on these wage levels".
In a statement, the Health Service Executive said the INMO's aggregated figures do not reflect the weather events in the first four months of the year, which it said impacted significantly on trolley figures.
It said that since April there has been a consistent improvement in trolley figures month by month compared to 2017, but the number of patients attending emergency departments continues to increase, while the number of people aged 75 and over who need to be admitted to hospital has risen by around 5% year on year.
The HSE said it "truly regrets" that any patient should have to wait on trolleys for admission to hospital beds, but all hospitals and communities "are doing their utmost to keep this number as low as feasibly possible".