YOU'VE SEEN THE OLD WESTERN movies when someone who has been shot is given a bullet to clench between his teeth so he won't bite his tongue off during surgery. Prior to the advent of anesthesia in the mid-1800s, even the most modest of surgeries were usually excruciatingly painful for patients. Since then, the field of anesthesiology has advanced significantly, offering patients a painless, comfortable, and safe surgical experience. Each year in the...