Anesthesia comes in three main types. Local anesthesia, the mildest form, merely numbs a very small area, such as a single tooth. Regional anesthesia desensitizes a large section of someone's body by injecting drugs into the spine that block nerve signals to the brain. Often a patient getting regional anesthesia also takes a relatively small dose of a powerful sedative drug, such as propofol—not enough to put them under but enough to alter brain activity in a way that makes the person less aware and responsive.
Surgeons may get more glory, but anesthesiologists probably play the most vital role in keeping you alive during surgery. They're the last face you see before you're put into a medicated sleep so deep you don't even notice that your body is being peeled open.
Between keeping track of your heart rate, breathing, and brain functions, an anesthesiologist also needs to be familiar with the ins and outs of the procedure so they can adjust sedatives and painkillers—without causing complications.
The new “perioperative information management systems” include software on touchscreen-enabled computers that can warn doctors if things are going south, keep track of the surgeon's workflows, and document every step of the procedure. All are essential when surgeries last up to 16 hours and docs need to pass the reins to a fresh pair of eyes.