Understanding Anesthesia and Common Side Effects

Modern anesthesia—using a combination of medications to prevent patients from feeling pain, moving or being aware during surgery—has been around since the 1840s. Today it is a highly nuanced field of medicine that is practiced in a variety of ways on thousands of patients in the U.S. every day.

Anesthesia is very safe, but it does have some common, usually mild side effects. UNC Health anesthesiologist Jenny Eskildsen, MD, explains what side effects you might experience with anesthesia. But first, it’s helpful to understand the types of anesthesia.

Types of Anesthesia

General anesthesia

General anesthesia uses medications to reduce pain, awareness and movement. It is delivered through intravenous medications and inhaled vapors. Under general anesthesia, a patient is unconscious and does not react to the stimulus of the surgery. It is used for longer or more invasive procedures.

Conscious sedation

Conscious sedation consists of medication to relieve pain and decrease anxiety, and it is typically administered through an IV. There are levels of sedation, from light to deep, that affect a patient’s awareness. It is used for procedures that do not require the patient to be unconscious, such as endoscopies.

Regional anesthesia

Regional anesthesia targets nerves in a certain location of the body to block pain in just one area, like an arm or a leg. Procedures to block nerve function in this manner are commonly referred to as nerve blocks and are delivered via injection. An epidural is a type of nerve block frequently used to reduce pain during childbirth without inhibiting a mother’s awareness during delivery.

Local anesthesia

Local anesthesia is numbing medication injected into a specific area, affecting a small area of the body without impairing awareness. It’s commonly used in dental procedures, for smaller cuts that require stitches and for biopsies. Local anesthesia also can be a topical cream.

While regional and local anesthesia do not typically require a patient to be unconscious, they also can be used under general anesthesia. For example, during a knee replacement surgery, local anesthesia may be injected around the knee joint, regional anesthesia can be used to block pain in the leg, and general anesthesia may be used to make the patient unconscious.

Common Side Effects of Anesthesia


Many patients who undergo anesthesia report feeling nauseated or vomiting. This most often happens within the first couple of hours or days after surgery. The medications used during anesthesia can cause this sensation, which may be worsened by the type of procedure, such as abdominal surgery. Because nausea is such a well-known side effect of anesthesia, patients are usually given anti-nausea medication to prevent it from happening.

Dry Mouth

Dry mouth is actually a potential side effect of the anti-nausea medication.

“We know that nausea can be very uncomfortable for patients, so we try to avoid that side effect by using preventive medications,” Dr. Eskildsen says. “We weigh the risks and benefits of each additional medication for each individual.”

Anesthesiologists will talk to patients beforehand to explain that “while we can use a specific drug to avoid nausea, it’s possible we create the experience of dry mouth,” Dr. Eskildsen says. Typically, patients prefer dry mouth to nausea.

Sore Throat

“In general anesthesia, we sometimes place a breathing device into the back of the mouth or throat to help a patient maintain normal breathing throughout surgery,” Dr. Eskildsen says. “While the patient is not aware of a breathing device being placed or removed under general anesthesia, these devices may cause a sore throat.”


“Feeling groggy or tired for some period of time after surgery is common, but it is medication- and surgery-specific,” Dr. Eskildsen says. “If you have a medication that is cleared more slowly from your body and/or you have a longer surgery, you may feel a little groggy for longer.”

Difficulty Urinating or Constipation

Sometimes the medications used for anesthesia can make it more difficult for people to urinate or have a bowel movement after surgery. This can happen when the lower half of the body is numbed for surgery, and this side effect is usually alleviated when the numbing sensation wears off. Urinary retention and slowing of the bowels are also known potential side effects of opioid-type pain medications.

The Patient Process

Dr. Eskildsen says in each situation, her team crafts an anesthetic depending on the needs of the patient, the task of the surgeon and the goals of the surgery. Additional medications to help with anxiety or to control blood pressure or heart rate are also used during anesthesia. This customized anesthesia plan is explained to patients before the surgery, along with possible side effects that could occur.

“It is imperative for us, as a patient’s anesthesia team, to be sure the patient is truly informed in giving us their permission to move forward with our specific anesthesia plan,” Dr. Eskildsen says.

Patients spend time in the recovery room after surgery with nurses who can address any side effects that may happen and make sure they are recovering as expected. A physician team is on hand to manage any medical concerns that might arise after surgery.

Talk to your doctor if you have an upcoming procedure that requires a form of anesthesia, and you have questions about it. Need a doctor? Find one near you.