Whistleblower and family of cancer patient Carmen Walker who bled to death write to Solicitor General Una Jagose to seek new Coroner's inquest

Carmen Walker, pictured shortly before her death, was recognised in the Whanganui Chronicle paper as one of the most positive people in town. Photo / Stuart Munro.

A whistleblower doctor and the family of a woman who bled to death during cancer treatment for melanoma have written to the Solicitor-General seeking a new Coroner's hearing to investigate why she died.

They say the questions raised by the death of Carmen Walker, a well-known Whanganui woman and otherwise fit 77-year-old, have not been answered.

In the original findings, the Coroner ruled on cause of death without investigating the standard of medical treatment, while the health watchdog body later criticised the medical care but noted the Coroner had already ruled on cause of death.

"It's hard to believe someone could die in circumstances like this and nothing happens," says her son Craig Walker.

"It just feels like Mum's death was swept under the carpet."

As first reported by the Weekend Herald, Carmen Walker underwent a palliative treatment called isolated limb infusion (ILI), where doctors cut off the circulation to a limb and infuse a highly concentrated chemotherapy agent to "bathe" the cancerous cells.

At the end of the treatment, tainted blood is drained into a waste bucket and the limb "washed out" with solution before the tourniquets are released.

Craig Walker, with wife Linda, says it's hard to believe his mother Carmen could die during treatment. Photo / Stuart Munro

It was at this point Walker's that blood pressure dropped and her heart stopped.

Despite being resuscitated, she died in Waikato Hospital later that night.

Instead of holding an inquest, Coroner Gordon Matenga determined the cause of death for Walker on the basis of the surgeon's report and the autopsy.

"High on the list" of possible contributing factors, wrote the surgeon, was that the tourniquets had not completely isolated Walker's leg, as her arteries were hardened from calcification.

This would mean blood from her body seeped under the tourniquet and into her leg, then drained into the waste bucket during the "washout phase".

Adam Greenbaum, consultant plastic and reconstructive surgeon, has written to the Solicitor-General. Photo / Alan Gibson.

Coroner Matenga ruled Walker died of "cardiogenic shock" - where the heart suddenly can't pump enough blood around the body - according to his seven-paragraph ruling released in April 2011.

But he did not examine why this happened, or whether the care given to Walker was satisfactory.

His findings were also concluded before the internal investigation into the "sentinel event" at Waikato DHB had started.

Dr Adam Greenbaum, who observed the procedure and attempted to later resuscitate Walker, was concerned at not being interviewed as part of the internal DHB investigation.

He laid a complaint with Health and Disability Commissioner Anthony Hill about the care given to Walker.

Craig and Linda Walker, the son and daughter-in-law of Carmen Walker [pictured in foreground], want answers over her death. Photo / Stuart Munro.

In a letter to Hill about the complaint, the then DHB chief executive Craig Climo described Greenbaum as "vexatious" after an employment dispute settled out of court.

However, Associate Professor Susan Neuhaus, the independent expert engaged by the HDC, found a number of problems after Greenbaum's complaint.

In her opinion, Walker most likely died from undetected blood loss during the "washout" phase.

This was disputed by the lead surgeon who previously told the Coroner it was "high on the list" of contributing factors.

He now said it was "impossible" - based on maximum flow rates - for Walker to have suffered massive blood loss during the washout phase.

In his opinion, the surgeon said undetected internal bleeding was the likely source of the blood loss.

As the washout fluid was not measured - ironically, one of the identified failings - Hill said he was unable to determine the cause of the blood loss.

But he found aspects of the care of Walker were "suboptimal".

Solicitor-General Una Jagose QC has the power to order a new Coroner's hearing. Photo / Mark Mitchell.

"A procedure of this kind must have adequate systems in place to ensure the early detection of serious complications," Hill wrote in his 2013 findings.

"It is my view that where a vascular procedure involves the removal of a significant volume of blood from a patient, there should be systems in place to alert the surgical team."

Hill took no further action in the case as the DHB no longer performed isolated limb infusion, so there was no ongoing risk to the public.

Craig Walker and Greenbaum have now written to the Solicitor-General, Una Jagose QC, asking her to open a new Coronial inquest to hear all the evidence together.

A spokeswoman for Crown Law said any decision on whether a new inquiry should be ordered requires "careful analysis of the facts and law and can take some months to complete, depending on the complexity of the subject matter".