How long do the fatigue and “brain fog” last after general anesthesia for surgery?

It depends – on your age, the specific drugs used, how long the surgery took and how healthy you were to start with. These days, most general anesthesia drugs are fairly short-acting, which means you wake up quickly and the drugs are mostly out of your system within a few hours, said Dr. Carl Rosow, an anesthesiologist at Massachusetts General Hospital.