The strike will result in hundreds of elective surgeries being postponed or cancelled, at a high cost to SDHB revenue.
The SDHB is under strict instructions from Health Minister David Clark to rein in a deficit that topped $25million, according to the most recent information released by the Ministry of Health.
This year it has prioritised reaching and exceeding its elective surgery targets to earn as much revenue as possible.
The SDHB told Parliament's health select committee during its annual review that work had already led to a ''financial benefit''.
The last SDHB commissioner's meeting was told by early March, despite four earlier 48-hour strikes by members of the New Zealand Resident Doctors' Association, elective surgeries remained well in surplus.
''We were able to maintain approximately 80% of our lists through these strikes as a little less than half of the RMOs [resident medical officers] either chose not to strike or had already joined the alternative Stonz (Speciality Trainees Of New Zealand) union,'' SDHB specialist services executive director Patrick Ng said.
However, he warned commissioners that any threatened longer strike could wipe out the progress surgical teams had made.
Yesterday, the SDHB said the RDA strike, scheduled to run from April 29-May 4, would have considerable effect on hospital health services.
''We won't know how many RDA members will show up to work until the strike days, and, because of this uncertainty, some electives and outpatients clinics will have to be postponed as a precaution,'' SDHB chief executive Chris Fleming said.
''Patient health and safety is our foremost concern and we're working to accommodate as many planned surgeries and clinics as possible.''
That comes at an added cost to the SDHB as senior, more expensive, doctors are called on to cover for junior colleagues.
SDHB hospital advisory committee meeting papers show that in February, senior medical staff costs were around $1million over budget, a cost it said was mostly driven by payments for strike cover.
''Patients whose planned surgery or appointments are to be postponed due to the NZRDA strike will be contacted directly by phone, text or letter,'' Mr Fleming said.
Emergency departments will remain open and urgent surgeries, cancer treatments, renal dialysis, most maternity services and intensive care would continue.
DHBs and the union are to meet soon in Employment Relations Authority-brokered facilitation talks, but a date has not been confirmed and the strike is still expected to go ahead as planned.
''We remain absolutely committed to trying to work with the other DHBs and the RDA to find a solution that will work for all parties,'' Mr Fleming said.
The dispute between the RDA and district health boards centres on proposed rostering changes.
DHBs want to vary existing ''safe staffing'' rosters to allow greater flexibility, while the RDA opposes any alteration to work conditions.
