How Anesthesia Works

General Anesthesia Administration and Recovery

So how does a person "go under"? General anesthesia may be administered via gas, an IV line or a combination of both. Often, patients are first given an IV injection to induce unconsciousness, then gas to prolong and maintain the effect. (Some injected anesthetics can maintain the correct level of anesthesia without the use of gas.) The gas is usually isoflurane or desflurane combined with nitrous oxide.

Ketamine, sedatives (such as Valium) and depressants like Sodium Pentothal may be injected into an IV that was inserted prior to surgery. In addition, the person administering anesthesia might give you a muscle relaxant to ensure deeper paralysis, especially if your operation involves major organs.


As surgery ends, the gases are turned off and the IV anesthetic is discontinued. Patients go to a PACU (post-anesthesia care unit) where they are closely monitored. Often, you'll be given warm IV fluids to counteract both the dehydration that results from anesthesia as well as shivering from changes in body temperature. As the analgesic effect of the anesthetic wears off, you'd also receive some sort of pain relief -- an oral medication or even morphine, depending on the surgery. Some people recover within an hour, while others take longer to completely awaken.

After waking up, it's possible you'll deal with lasting side effects: vomiting, nausea and numbness in the area where surgery was performed. You'll probably feel disoriented and require assistance to get around.

It's also important to mention that there are serious risks associated with general anesthesia, including suffocation, allergic reaction, organ failure, stroke and death. These are concerns you should discuss with your doctor before your surgery.

Anesthesia has come a long way since its earliest days. Next, we'll take a brief look at the history of anesthesia.