Fair enough for the brain surgeon- but presumably he would still plan his loo breaks so they are not at the absolutely most critical moment? Nobody said children were not to have loo breaks at all, you know. Nor is anybody suggesting that a child who has bladder or bowel problems should not have a toilet pass.
The only op I've had was my Caesarian, but I must say I would have been a little...well, pissed off, if the operating surgeon had cut me open, stuck his hands in to lift ds out and then said 'oh, I'll just pop to the loo' and gone off and left me lying there with my stomach open. I would expect him to be able to go before he cut me open and then last that long.
The comparison with uti's in the caring profession is perhaps a little irrelevant, as school children have far more frequent breaks anyway; they are not in the position of someone who has to hold it for hours on end.
For me as a uni teacher, if 5 students decided to take loo breaks in the middle of the lecture, the disruption of them getting in and out of the rows of lecture seats would mean 20 minutes lost for everybody out of a 90 minute session, because of the noise and disruption; also, 5 minutes lost for the absent student. There would be a lot of people failing their exams if this habit caught on. I can't keep on and on repeating stuff because people keep popping off; we'd never get through the course. And if I regularly took 5 minutes myself, the students would feel I was wasting my time. I would always be sympathetic with genuine needs, but that is different.