I used to work with animals too and our vet always kept the toy breeds overnight. Something about how it doesn't take much for their little bodies to go from ok to bad to worse. It was just a precaution mostly from the eating standpoint. When dogs get upset they dont eat. A lab, no big deal. A toy, huge deal! They dont have much to begin with, missing a few meals and trying to get over spaying is really hard on them.