A nurse has admitted administering an overdose of salt to a baby who later died, a medical tribunal heard.
The concentration of sodium chloride was approximately 10 times more than expected from the prescription for four-month-old Samuel McIntosh, who died at Nottingham's Queen's Medical Centre (QMC) in July 2009.
An inquest into the death the following year heard that two nurses who were involved in a "dreadful mistake" which led to the death could not explain how the error occurred.
The inquest heard that Sister Karen Thomas and staff nurse Louisa Swinburn were "distracted" by another staff member as they prepared a solution to correct Samuel's low salt levels.
As a result of the mistake, Samuel was wrongly given 50ml of a sodium chloride solution despite a registrar prescribing just 5ml.
Tests conducted on a syringe after the mistake was spotted showed that the sodium chloride had also not been mixed with dextrose, as required by the prescription.
The error meant the infusion given to Samuel was 10 times the required concentration, causing swelling to his brain from which he died.
A fitness to practise panel of the conduct and competence committee of the Nursing and Midwifery Council in London heard that Ms Swinburn, who was not present for the hearing, had admitted administering an overdose of sodium chloride to Samuel, who is being called Baby A for the purposes of the hearing.
She admitted that the overdose related to a concentration of sodium chloride approximately 10 times that expected from the prescription.
She has also admitted posting on Facebook, on or around 23 June 2009, a photo of herself on duty at the Nottingham University Hospitals NHS Trust and the baby.
This was without the consent of the Trust or the baby's parents.
She denies charges that on the nightshift of 22-23 June 2009, she fell asleep while on duty, and that she appeared to be asleep in the photo.
The panel is to consider whether her alleged actions amounted to misconduct and if her fitness to practise is impaired.
At the inquest, Paul Balen, the solicitor acting for Samuel's parents Robert and Sarah McIntosh, urged the Nottingham Coroner, Dr Nigel Chapman, to consider a verdict of unlawful killing.
But Dr Chapman recorded a narrative verdict after ruling that Samuel died after a "drug error" on the high dependency unit at the QMC.
Ms Thomas, who was in charge of the unit, told the inquest that she had no clear memory of what she actually did.
There had been "a bit of an interruption", she said.
Ms Swinburn told the inquest she could not recall opening five 10ml vials of sodium chloride, saying: "Nothing occurred to me at all that we had made an error."
Samuel had been born prematurely at Nottingham's City Hospital on 1 March 2009 and weighed 1lb 4oz (580g) - around a sixth of the normal weight for a full-term baby.
He was transferred to the QMC aged 18 days and although he required intravenous feeding and underwent a bowel operation and eye surgery, his weight eventually rose to 6lb 3oz (2.8kg) and he would have been expected to survive.
Dr Chapman said there was no doubt that a dreadful mistake had taken place, but ruled that it did not fall into the category of a gross failure.
Paediatrician Dr Catherine Smith, who was working at the hospital as a specialist registrar, told Monday's hearing that the baby had low sodium levels and she prescribed a correction for them.
"Low sodium levels can lead to seizures and the patient can fit and lose consciousness,' she said.
The calculations she made were correct, she added, and she went through them with Karen Thomas, who appeared to understand and agree with them.
"It was normal practice in this sort of situation," Dr Smith said.
She accepted that there was potential for the instructions to be misinterpreted. "I think that's one of the changes that has been made, subsequent to this, but this form was in use every day."
Asked if the number of vials of sodium chloride they would have needed to prepare the faulty infusion should have rung "alarm bells", she said: "Yes."
Dr Stephen Wardle, consultant neonatologist at the Trust, said doctors explained to the parents that the baby had a low sodium level and had been accidentally been given too much replacement sodium.
He said the chart had been changed to improve clarity, making the doses and volumes required more clear.
"We have undertaken a review of practices including making sure people preparing infusions wear tabards to make sure they are not interrupted,' he added.
The hearing, which is expected to last three to four days, was adjourned until Tuesday.
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