How can so many posters be so sure he is in pain?
No one knows, however when I have had an operation I wake up with a sore throat from being intubated, this child has been intubated for months.
When you are on a ventilator your lungs have to be, well not a nice way to put it, have any mucus siphoned/sucked out added to that positive pressure is being used to inflate the lungs.
He is also on IV meds and I assume a feeding tube.
Each of these can cause pain.
From what I have read his organs will probably start to breakdown soon, have you ever had a kidney infection?
It is fair to assume any child with this going on is undergoing things that cause pain, the only difference here is that he may be too brain damaged to feel it.
On balance it's better to give pain relief. As for starting with calpol (I know it wasn't you) I think they will go by what other patients with the same interventions but able to communicate tell them.