A 48-hour stoppage by SIPTU and Unite members in the National Ambulance Service is set to take place on 19 May, following the 24-strike action, which ended at 8am this morning.
The HSE said yesterday that the action had a "significant impact" on ambulance services, resulting in longer than usual response times.
Pickets were placed at ambulance bases around the country as part of the action but striking workers said they did respond to life-threatening emergencies.
The full impact of the strike will become clearer today, with the HSE saying it has been closely monitoring the situation.
A work-to-rule which began on Monday is continuing and unions have warned that in addition to this week's action, there will be a 48-hour stoppage on 19 May, a 72-hour stoppage on 26 May, and further strike action planned for June.
The dispute involves emergency medical technicians, paramedics, advanced paramedics, specialist paramedics and paramedic supervisors.
Unions have accused the HSE of failing to implement the recommendations of an independent report on updating staff salary scales to reflect changes in responsibilities and workload.
The HSE said it regrets the decision to proceed with industrial action, adding that a previous set of proposals aimed at resolving the dispute, which would have delivered pay increases, were rejected by union members.
Unions say however that the proposals came with conditions, including changes to allowances, that were unacceptable to members.
The HSE has urged SIPTU and Unite to suspend the industrial action and return to the negotiating table.
Unions have said they would be willing to re-enter talks if they are held without preconditions.
