An official report into a baby girl's death has revealed she was given a fatal dose of calcium during heart surgery at Bristol Children's Hospital.
Abbie died after undergoing heart surgery in Bristol
Abbie Hattam, from Truro, was given the dose by a perfusionist - the scientist who prepared her heart bypass machine for the operation in May 2005.
A police inquiry into Abbie's death, who was aged five months, was dropped.
The report said perfusionist Richard Downes was under "considerable pressure" - he has returned to work.
Investigators also discovered Mr Downes had been receiving counselling and was under significant pressure to maintain services for several months before the operation because of staff shortages.
It was a recognised problem and the department had called for more perfusionists, but management at the hospital was slow to recruit, the report said.
Prior to Abbie's operation there had also been an argument between Mr Downes and heart surgeon Ash Pawade about the ongoing staffing problems.
Mark Gritten, author of the report, said: "It is likely to have made the team tense, but they were asked if they were happy to proceed and both said they were.
"Whilst they would be able to continue to work, it is likely that there would be an element of preoccupation in all the team as a result of this unusual event."
Among a number of recommendations, the report said more stringent checks should be carried when any doses of medication are given.
The Department of Health issued a statement saying: "The government is in the process of regulating perfusionists along with other groups of health care scientists."