A baby boy allegedly poisoned by nurse Lucy Letby had dangerously low blood sugar levels on three successive days, a court has heard.
Letby, 33, is said to have added artificial insulin to a bag of intravenous liquid the infant was receiving at the Countess of Chester Hospital’s neo-natal unit.
Jurors at Manchester Crown Court heard how the brain is reliant on a “constant supply” of glucose to function and the risks of low blood sugar included seizures, coma and death.
A medical expert told Manchester Crown Court that the youngster, Child L, suffered a hypoglycaemic episode which lasted from the morning of April 9 2016 to the middle of the afternoon on April 11.
Peter Hindmarsh, professor of paediatric endocrinology at University College London, said the results of a blood sample taken some time on the afternoon of April 9 meant he was “quite certain” that non-natural insulin was present in his system.
Nick Johnson KC, prosecuting, said: “So somebody gave insulin to (Child L)?”
Prof Hindmarsh replied: “Yes, I agree with that statement and I think we should add that it was not prescribed insulin.”
Giving evidence on Friday, he considered the most likely method of administration was intravenously into a bag of dextrose, a sugar supplement, which was connected to Child L’s drip.
Prof Hindmarsh said the volume of insulin required would be “quite small” and would not be noticeable in the bag or from a routine stock check.
He added: “Once in the bag it’s – in a sense – sealed off from you being able to detect it by smell.”
Jurors heard the dextrose concentration was increased as medics tried to bring Child L’s blood sugar levels up – which necessitated a change of bag – and the rate of infusion was also stepped up.
Prof Hindmarsh said despite that there was “not really much change in the glucose measurements which would imply there was ongoing insulin present and ongoing insulin action”.
He told the court that insulin could “potentially” have been added to at least three dextrose bags if the giving sets were also changed.
Prof Hindmarsh also raised the possibility that if the giving set remained the same then insulin could stick to its plastic, come off and then release into the bag.
He agreed with Ben Myers KC, defending, that “sticky insulin” would eventually run out.
Mr Myers asked: “It is the case that sticky insulin could be operative over a similar period?”
Prof Hindmarsh replied: “I don’t think anyone has done this sort of study to be honest. I think the answer is I don’t know.”
He told Mr Myers the “relatively steady” blood sugar levels did not seem to be influenced by the increased infusion rates.
Mr Myers asked: “Would that be more consistent with it being added to the bag as you go on, rather than the sticky insulin?”
Prof Hindmarsh replied: “Yes.”
Letby is also accused of attempting to murder Child L’s twin brother, Child M, who collapsed at 4pm on April 9.
She is said to have injected air into his bloodstream while he too was on an intravenous drip in the same nursery as his brother.
Letby, originally from Hereford, denies the murder of seven babies and the attempted murder of 10 others between June 2015 and June 2016.
The trial continues on Monday.
