Why Is My Grandmother Unconscious Post Surgery?

Hi ~ My grandmother had surgery on Monday afternoon for an Aortic Anurism in her abdomen. Monday evening she had a secondary surgery for a tear in her Aorta (not related to the surgery) and to bypass a blood clot that formed in her leg. My question is: should we be concerned that she has not been concious since the surgery? The doctors at the hospital keep telling my mother and her siblings that my grandmother is stable and everything is fine but I'm not sure based on the fact that she has not been concious since Monday night. Please advise. Thanks!