Anyone who has had major surgery may be surprised to learn that being "put to sleep" involves more than a shot of pentothal. Thanks to general anesthesia, people simply cannot remember much after they reach the operating room.

But from the moment surgery begins, the anesthesiologist is constantly busy with tasks that can mean the difference between life and death. He or she must frequently adjust the balance of various drugs used to begin, maintain, and reverse anesthesia; typically, 7 to 10...