The ones in the trap, yes, sedation was possible through the bars. Although that was not so easy either.
Actually, the vets I have dealt with with my ferals say it is pretty easy. Just put a blanket (which ideally would be covering the trap when it is brought in to calm kitty) over the trap and gas is piped in. Then when kitty is sedated it is easy to remove. They just ask for a carrier to be brought in so kitty doesn't have to go back in trap.
Just for future reference if you are working with the same vet. A full stomach can result in vomiting and aspiration while under anaesthetic. Probably not really a great idea IMO to have vet operate right away. I sincerely hope that vet tech is no longer working if that is the way he was extracting cats from carriers. He deserved every scratch he got IMO!
Congratulations on a fantastic record of capture/neuturing/release! Great to hear success stories!!