Rotherham Coroners Court was told that Louise Wood was given a massive overdose after developing breathing difficulties at Rotherham District General Hospital last year.
Lynda Wood, 36, of Thrybergh, Rotherham, South Yorks, gave birth to twins Natalie and Louise in September 1995. The girls were taken as a matter of routine to the neo-natal intensive-care unit, but Louise developed breathing difficulties when she was only 24 hours old.
The infant suffered a pneumo thorax - air escaping from the lungs into her chest cavity - and doctors decided to apply a chest drain.
The inquest heard that registrar Dr Vivian Michael decided to sedate Louise with morphine to relax her muscles and allow the process to be carried out. A baby ought to be given 10 micrograms of morphine per kilogram body weight. Louise, weighing 1.6kg, should have been injected with 16 micrograms.
The inquest heard that Senior House Officer Dr Hilary Evans told Dr Michael the correct dosage but then miscalculated and drew up 100 times the dose into two phials.
Paediatrician Dr John Puntis, who was called in by the coroner to review the medical case notes, said: "Dr Evans was a very new, very junior doctor, who had moved into the neo-natal ward, where drug doses would be completely unfamiliar and where the environment would be stressful.
"One would expect her to be familiar with the kind of dose that would be given to an adult."
Coroner Stanley Hooper, who described Dr Evans' actions as "damn silly or reckless", said her case notes had contained "seriously wrong" errors. "The notes are satisfactory, at least until the child was given a dose of morphine, which I will be hearing was 100 times what was appropriate," he said.
The medical staff tried to counteract the morphine overdose with Naloxone. However their efforts were unsuccessful.
Pathologist Professor Michael Green found the cause of death to be poisoning by morphine. Toxicologist Dr Robert Forrest, who tested a blood sample, found: "The concentrations of morphine in the blood sample are extremely high and are entirely compatible with a potentially fatal overdose." Professor Green said: "I regard this as an unnatural death."
No case histories exist on the effects of morphine overdoses on babies and Professor Green said he could not be certain "beyond reasonable doubt" that Louise had not died as a result of her weak lungs.
But he added: "The most likely cause of death in poisoning by morphine. It is a high probability."
Criminal courts require beyond reasonable doubt to be established as a cause of death; an inquest needs it only to be probability on the balance of evidence.
Professor Green said that the only comparison to be drawn was with heroin abusers who "die on the needle" between two and seven minutes after overdosing.
The overdose causes the heart and lungs to fail in adults and this would have happened in the case of Louise. The inquest continues.Reuse content