You can theoretically knock out Gunther Hermann, but not Anna Navarre.
I've gotten out of UNATCO without killing her, though, using the following method:
1) Make sure there's a living, conscious UNATCO trooper in one of the offices near the locked front door.
2) Injure Anna to the point where she runs away, or lock her in a cupboard or leave her downstairs or something (cloaking helps). Something to get her out of your hair.
3) Using boxes, furniture, potted plants, and other decorations, create a pathway straight from one of those offices to the locked door.
4) Injure the UNATCO trooper in that office until he wants to run away. The only place he'll have to go is through that door, so he'll unlock it for you.
It worked for me, anyway, although I think it took some fiddling and lots of loading/saving.
An alternative method, although I can't personally vouch for it, is to use something that makes an extreme amount of noise, preferably a large explosion, at the locked door, so the guard on the other side of the door (near the retinal scanner) hears it and investigates.