What Is General Anesthesia?

Before some types of surgery, you'll get medicine to make you sleep and prevent you from feeling pain. This medicine is called general anesthesia.

How Does It Work?

General anesthesia works by interrupting nerve signals in your brain and body. It prevents your brain from processing pain and from remembering what happened during your surgery.

A specially trained doctor or nurse, called an anesthesiologist, gives you general anesthesia and cares for you before, during, and after your surgery.

A nurse anesthetist and other team members may also be involved in your care. Your anesthesia team will check your breathing and other body functions while you're in surgery.

Before your surgery, you'll get anesthesia through an IV line that goes into a vein in your arm or hand. You might also breathe in gas through a mask. You should fall asleep within a couple of minutes.

Once you're asleep, the doctor might put a tube through your mouth into your windpipe. This tube ensures that you get enough oxygen during surgery. The doctor will first give you medicine to relax the muscles in your throat. You won't feel anything when the tube is inserted.

During surgery, the anesthesia team will check these and other body functions:

Your medical team will use these measurements to adjust your medications or give you more fluids or blood if you need them. They will also make sure you stay asleep and pain-free for the whole procedure.

After surgery, the doctor will stop your anesthesia medicines. You'll go to a recovery room, where you'll slowly wake up. The doctors and nurses will check to make sure you're not in pain and that you don't have any problems from the surgery or the anesthesia.

When Do You Get It?

Your doctor might give you general anesthesia if your procedure:

  • Takes a few hours or more
  • Affects your breathing
  • Is done over a large area of your body
  • Involves a major organ, such as your heart or brain
  • Could make you lose a lot of blood


When Should You Not Get It?

You and your doctor may decide it’s not the right choice for you if:

  • Your surgery is minor
  • The procedure is being done on a small part of your body (such as on your foot or face)

For these types of procedures, you might just need:

Local anesthesia: This prevents any pain in the small area of the surgery, but you stay awake.

Regional anesthesia: This numbs a larger area of your body, such as your legs, but you also stay awake.

What are the Risks and Side Effects?

You might feel a little groggy when you wake up from the anesthesia. Other common side effects from the medicine are:

Rarely, people can be very confused for a few days after their surgery. This is called delirium. Usually it goes away after about a week.

Some people have memory trouble after they get general anesthesia. This is more common in people with heart disease, lung disease, Alzheimer's, or Parkinson's disease. Your doctor should discuss all of these possible complications with you before your surgery.

General anesthesia is safe for most healthy people. Yet it can carry a greater chance of complications if you:

Very rarely, someone can still be awake after they get general anesthesia. Even more rarely, a person will feel pain during the surgery, but they won't be able to move or tell the doctor they're awake and in pain. Being awake during surgery can cause long-term emotional problems.

How to Prepare Before Surgery

You'll meet with your doctor and anesthesiologist before the surgery. They'll go over your surgery so you know what to expect. The anesthesiologist will ask you:

  • What medical conditions you have
  • Which medications you take, including over-the-counter medicines and herbal supplements
  • If you have any allergies, such as to eggs, soy, or any medications
  • If you smoke, drink alcohol, or take street drugs such as cocaine or marijuana
  • If you've ever had a reaction to anesthesia during a past surgery


Your doctor will tell you not to eat or drink anything but water for about 8 hours before your surgery. This is because general anesthesia relaxes your muscles, which can cause food from your stomach to get into your lungs.

You might need to stop taking certain medicines a week or more before your surgery. These include medications and herbal supplements that can make you bleed, such as:

Ask your doctor which medicines you can still take with a small sip of water on the morning of your surgery.

WebMD Medical Reference Reviewed by Carol DerSarkissian on December 28, 2018



American Society of Anesthesiologists: "Effects of Anesthesia."

Mayo Clinic: "General anesthesia: How you prepare," "General Anesthesia: Overview," "General anesthesia: Risks," "General Anesthesia: What you can expect," "General anesthesia: Why it's done."

MD Anderson Cancer Center: "What to know about general anesthesia."

National Health Service: "General anesthesia."

National Institute of General Medical Sciences: "Anesthesia Fact Sheet."

Nemours Foundation: "About Anesthesia."

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