The patient died on Monday, after presenting to Christchurch Hospital's Emergency Department (ED) last Sunday evening.
In a statement today, Richard French, chief medical officer Te Whatu Ora Waitaha Canterbury, confirmed the series of events that preceded the patient's death.
"The patient left the ED and deteriorated shortly after leaving and returned to the ED where they were seen immediately. Sadly, the patient did not respond to medical treatment and died the following day," French said.
"We acknowledge our ED was very busy during this period which meant wait times were longer than usual. Our heartfelt sympathies remain with the whānau at this difficult time."
The patient died after being transported to the hospital's intensive care unit [ICU].
Christchurch news outlet Chris Lynch Media reported the patient died from sepsis, but had been initially sent to the waiting room after being triaged by a nurse, and collapsed some time after this.
Sepsis is the body's extreme response to an infection.
The patient is then believed to have left the ED, but was forced to return to the hospital shortly after where they were placed in ICU and did not recover.
A formal review of the care provided to this person is underway, French confirmed.
In July, National Party health spokesman Dr Shane Reti cited data obtained by the Parliamentary Library, which he said showed that since 2017 there has been a "marked decline" in the number of people seen within six hours at an ED at hospitals across the country.
The latest data sourced by the Herald, for May 2022, shows the average wait time at an ED nationally was 287 minutes (a little under five hours), compared to 270 minutes in May 2021.
Te Whatu Ora – Health New Zealand said it is working "as quickly as possible" to implement changes and provide relief to a besieged health system, including expanding telehealth, which are consultations with a health practitioner via communication technology.
