The only reason my wife's involved an overnight stay was dehydration since she'd been unable to keep much of anything down for a couple days. That said, her surgery was scheduled after a pretty short series of doctor, ultrasound, surgeon, weekend, surgery.
I did spend two nights in the hospital (one before the surgery, one after), but I'm surprised that surgery would be considered outpatient under any circumstances. Do they really send people home immediately after putting them under and rooting around in their chest cavities?