Anaesthetic technicians at Rotorua Hospital are planning a seven-day strike next week, leaving the Lakes DHB "extremely disappointed".
APEX (Association of Professional and Executive Employees) union said in a statement the 168 hours of industrial action would start at 8am Monday and finish 8am the following Monday, on April 15.
All elective surgery that requires a general anaesthetic will be cancelled or postponed.
The 11 union members in Rotorua have been bargaining their collective agreement with the DHB since October 2017.
This strike will bring the total strike action by the technicians to 16 days, since October.
The DHB is "extremely disappointed" by the latest notice.
In a statement, Lakes DHB acting chief executive Nick Saville-Wood said some patients' surgery had been delayed by repeated strike action, and while staff had worked tirelessly to provide new dates, ongoing industrial action had made this extremely difficult.
"Lakes DHB is becoming increasingly concerned about our community being able to access hospital services as our priority is to ensure patient safety and wellbeing is maintained."
He said the DHB's anaesthetic technicians were valued.
"We have always bargained in good faith and will continue to do so with APEX and its members."
The union said the primary driver behind the latest strike was rest breaks.
Advocate Luke Coxon said for decades there had been a provision for a 12-hour break when 10 hours or more had been worked, but the Lakes District Health Board had stopped the practice.
Coxon said an agreement was reached in bargaining to reinstate the 12-hour break, however, he said the DHB rescinded its agreement in December.
He said during the previous strike, patients were transferred to private hospitals at an "enormous" cost to both the DHB and taxpayer.
"We now have the outrageous situation where approximately 150 surgeries will be cancelled, because Lakes DHB has refused to provide the anaesthetic technicians with adequate rest breaks. These breaks are essential for the safety of both patients and our members."
Coxon said the anaesthetic technicians would still be available for life-preserving acute surgery during the strike and the public would not be placed at risk.
Saville-Wood said the union was trying to force conditions on the Lakes DHB that were different from those accepted by APEX for other DHBs for the same workforce.
He said reasonable solutions offered by the DHB to settle the concerns were rejected.
Saville-Wood said the current agreement provides a nine-hour break between qualifying work periods.
"Given that anaesthetic technicians under the APEX and PSA unions have settled at other DHBs, without raising the issue of a 12-hour break, I have to ask the question, why is the APEX union and its Rotorua members targeting Lakes DHB?"