Inspiring teenager Amy Allan, 14, who has been remembered with a first aid award in her name, died at the world famous children's hospital in September last year.
Her death came 23 days after the enthusiastic first-aider, from Dalry, Ayrshire, having an op to cure a worsening curvature of her spine.
Doctors caring for her immediately after her operation were asked about a possible delay in giving her an emergency therapy, ECMO - a technique which re-oxygenates blood outside the body.
She was taken off the ventilator at 11.20pm on September 4 2018 but, despite deteriorating rapidly, was not on ECMO until 8am the next day.
An intensive care doctor with eight years of experience with ECMO, Dr Rahit Saxena, who put Amy on ECMO agreed with the family's counsel, Edward Ramsay, that taking her off the ventilator in the night - when fewer doctors were at the hospital for ECMO - was not ideal.
He agreed he should have been told it might need to happen beforehand.
Mr Ramsay said: "Given all the evidence about how difficult it is to assemble the [ECMO] team at 4am then why hadn't you been alerted that this might need to happen?
"It stands to reason that doing this in the middle of the night was the worst time do do it.
Dr Saxena said: "Yes, we have an expectation that if someone has been listed for ECMO support I should know about it. No-one informed me."
The teenager, described as having "complex" conditions, was diagnosed with a genetic condition called Noonan Syndrome which severely affected both her heart and lungs.
She was born with holes in her heart and needed surgery to close them when she was nine weeks old.
She was then diagnosed with a cardiac condition called Hypertrophic Cardiomyopathy - an unhealthy thickening of her heart muscle.
At four she was diagnosed with Pulmonary Hypertension - high blood pressure in her lungs.
An inquest into her death, which began yesterday (MONDAY) at St Pancras Coroners Court in London, has revealed that the Scottish teen may have died as a result of being taken off a ventilator too early.
An independent expert doctor addressing the court on the hearing's first day, Dr Steven Playfor, said that decision was a mistake.
He said: "She suffered very severe and prompt deterioration in her status. I can say that with a high degree of certainty."
The inquest continues.