A four-year-old boy who died following major heart surgery on a controversial hospital ward should have been receiving high-dependency care when he suffered a cardiac arrest, an inquest heard on Wednesday.

Sean Turner died in March 2012 from a brain haemorrhage after previously suffering a cardiac arrest - six weeks after he underwent vital corrective heart surgery at Bristol Children’s Hospital.

His parents, Steve, 47, and Yolanda Turner, 45, have given harrowing accounts to the inquest of how they begged doctors and nurses on Ward 32 to help their desperately ill son.

Mr and Ms Turner, from Warminster, Wiltshire, claim their son’s death was not isolated and other children with heart problems have died at the hospital, including Luke Jenkins, aged seven, from Cardiff.

Up to 10 families are believed to be taking legal action against the University Hospitals Bristol Foundation Trust over treatment on ward 32.

Sean had undergone a Fontan procedure on 25 January and had been given the drug heparin to try and prevent blood clots from forming - a common occurrence in heart surgery patients.

Sean had been moved from the hospital’s paediatric intensive care unit (Picu) to ward 32 within 18 hours of surgery but after suffering a collapse he was transferred back to intensive care, where he stayed for 11 days.

On 9 February he returned to Ward 32 where he remained until suffering the cardiac arrest on 16 February.

The inquest has heard that at the time of Sean’s death ward 32 did not have a high-dependency unit - one level down from intensive care with a nursing to patient ratio of 1:2 - and there were problems with staffing levels.

Since Sean’s death a high-dependency unit has been created on the ward.

Duncan Macrae, a consultant in paediatric intensive care at the Royal Brompton Hospital, had been asked to give evidence to the inquest at Avon Coroner’s Court as an expert witness, having reviewed Sean’s medical notes.

“His ongoing care requirements around that time were relatively high because he had high chest drain losses,” Dr Macrae said.

“He needed high dependency care, which I take to be one nurse to look after two patients. I was not sure that’s what he received on ward 32 but that’s what he should have received.”

Avon Coroner Maria Voisin asked Dr Macrae whether the cardiac arrest was preventable, to which he replied: “I believe it was. I cannot see any link between the cardiac arrest and Sean’s chest drain losses.”

Dr Macrae said that from 12 February Sean’s condition was beginning to deteriorate - with rising heart rate, vomiting and nausea - and he should have been seen by a cardiac consultant.

“This is a somewhat similar group of symptoms that he had when he developed the cardiac tamponade (fluid on the heart) on the first occasion,” Dr Macrae said.

“These are non-specific signs of something going on and symptoms that ought to have been addressed and perhaps led to an earlier discovery of the tamponade on February 16, sadly in relation to the cardiac arrest.

“I think it would have been appropriate for there to have been a review by a consultant cardiologist in the first instance and obtain an echocardiogram to exclude a cardiac tamponade.

“If the right people had been there and asked the right questions he could have been moved to the paediatric intensive care unit or an echocardiograph done, which might have led to more thought and steps taken to his improve his condition.”

The court has heard that Sean was given the drug heparin to try and prevent blood clots from forming - a common occurrence in heart surgery patients.

Experts have given evidence that Sean’s heparin levels were not within the target range set by doctors, which Dr Macrae said would have been difficult to achieve given the post-surgery fluid losses from his chest.

“The fluid losses were the highest I have seen in a child with this type of surgery, which I think it made it difficult to achieve levels of anti-coagulation,” Dr Macrae said.

“If you have losses of several litres a day of plasma it is very difficult to get the balance between anti-coagulation and coagulation.

“He subsequently did develop a thrombosis.

“I think it would be entirely appropriate to consider him a low risk case, so therefore surprising that he developed such high chest drain losses.

“Something had clearly changed in his circulation and it had not adapted to the changes that the Fontan procedure had put in place.”

Ms Voisin asked Dr Macrae whether “on the balance of probabilities” keeping Sean within the heparin range of 0.3 to 0.7 units/ml would have prevented the blood clot from developing.

Dr Macrae replied: “I do not think it would have prevented it, period.”

He said that in his opinion Sean had died from a “combination of complications” following heart surgery.

And because of Sean’s “really, really high” chest drain losses, fenestration - a follow up surgical procedure that makes a hole between the Fontan tunnel and the heart - may have been a “short term fix” to reduce the losses but would not have stopped them completely.

“Certainly I am aware of cases that losses can be reduced by 50 per cent in patients with fenestration compared to those without,” he said.

“But in Sean’s case that may have still have left him with high drain losses.”

Ms Voisin is due to record her conclusion on Thursday.

The lawyers representing both Mr and Mrs Turner and the health trust have submitted that the appropriate conclusion is a narrative.

Adam Korn, for Mr and Ms Turner, did not invite the coroner to consider the issue of neglect because the evidence did not support a finding of “gross failures to provide basic care”.

Instead he asked the coroner to consider making a prevention of future deaths report.

The inquest was adjourned until Thursday.