Two Wairarapa patients died in the past year after medication errors, a health report shows.
The Health Quality and Safety Commission's annual serious and sentinel events report says one person was given the wrong blood thinning drug while another accidentally overdosed after being left over-the-counter medication contrary to their care plan.
Their deaths were among four serious incidents detailed in the report released this week.
The two other Wairarapa cases included a patient who died on the operating table from a lung clot. The other case involved a CT scan given to the wrong patient.
Of the four cases, two occurred in the community and two in hospital.
No more details about the incidents were given.
Quality, safety and risk director Cate Tyrer said all the events had been investigated.
"An unexpected death is very sad and affects everyone involved," she said.
"We need to do everything we can to understand how and why, to prevent it happening again if possible."
Board chief executive Tracey Adamson said the organisation was committed to providing the highest quality care for patients.
"Any preventable error is unacceptable and the DHB seeks to learn from it."
Nationally, 360 serious and sentinel events were reported in the 2011/12 financial year, down from 370 in the previous year.
Ninety-one of those cases resulted in patient deaths, compared with 86 in 2010/11.
Commission chairman Alan Merry stressed not all reported events were preventable but many involved errors which should not have happened. "In some tragic cases, errors resulted in serious injury or death.
"Each event has a name, a face and a family, and we should view these incidents through their eyes."
Falls continue to make up the bulk of serious and sentinel events in hospitals, counting for 47 per cent of all cases. However, nine patients had surgical instruments or swabs left inside them and 10 others underwent the wrong procedure or treatment. There were also 18 reported mistakes with patient medication.
But a jump in clinical management errors, specifically those relating to treatment delays, is flagged as a concern.
Seventeen cases of delayed treatment due to failures in hospital systems were reported last year. But the commission said the actual number of incidents was likely to be much higher. APNZ