The Side Effects and Complications of General Anesthesia

There are many potential side effects associated with the use of anesthesia for surgeries and procedures. They vary widely from minor issues to significant and potentially life-threatening complications.

Man going under anesthesia
Caiaimage / Sam Edwards / Getty Images

Severe adverse effects caused by anesthesia are uncommon and most people will experience no issues or only minor ones in the hours and days following their procedure. However, your risk of anesthesia complications increases if you have brain, heart, lung, or kidney disease, abuse drugs or alcohol, smoke, or have allergies to anesthetic medications or a family history of such allergies.

The type and severity of anesthesia side effects a person experiences are affected by factors such as:

  • Current health and medical history
  • The type of anesthesia
  • The duration of anesthesia treatment
  • The nature of the procedure

For example, a child who is given anesthesia for one hour for an appendix surgery and has no other health issues will likely experience fewer complications than an 85-year-old diabetic smoker who is having several hours of anesthesia during open-heart surgery.

General Anesthesia Explained

General anesthesia is used during surgeries in a hospital or surgical center setting. Medication is given both as an inhaled gas and through an IV before and during surgery. During this type of sedation, the patient is completely unaware of their surroundings and does not experience pain as they are in a state of consciousness that's much deeper than sleep.

When you have general anesthesia, you need a breathing tube placed in your throat so you can be on a ventilator during surgery. This is because general anesthesia medications paralyze the muscles of the body, including the muscles that you use to breathe.

Muscle paralysis is particularly important during delicate surgeries, but it can also lead to complications caused by a prolonged lack of movement.

The risks of general anesthesia are not the only risks you need to be aware of prior to your procedure—there are also risks of the surgery itself. Every procedure carries its own characteristic potential risk factors that are unrelated to the anesthesia.

For example, a patient having surgery to remove the appendix would have a risk of infection spreading from the appendix, as well as the potential for an infection in the incision, which is unrelated to the risks of general anesthesia.

Common Issues

Common problems associated with general anesthesia should resolve within a few hours. Your surgical team will often take measures to prevent them before and during surgery, then monitor you for signs of problems and treat them (if they occur) after your procedure.

Nausea and Vomiting

The most common complication after general anesthesia is nausea and vomiting. Postoperative nausea and vomiting (PONV) are easier to prevent than treat. Medications can be used for prevention as well as for treatment.

The best predictor of whether or not you will experience postoperative nausea and vomiting is having a history of nausea and vomiting after previous surgery. Those who have had it in the past are much more likely to experience it again and are typically pre-medicated with anti-nausea medication to prevent it from happening again.

Sore Throat or Hoarseness

After having the breathing tube placed, you may develop a sore throat or a hoarse voice, particularly if your surgery was a long one. While this typically cannot be prevented, sore throat sprays, lozenges, and other medications used to reduce throat pain are appropriate in the days immediately following surgery.

Hoarseness that isn’t improving more than 5 to 7 days after surgery should be addressed with a healthcare provider.

Dry Mouth

Dry mouth can be a result of the fact that the patient has been unable to eat for hours beforehand and also can be due to some of the medications used. This should resolve within 24 hours after surgery, and you can use water or ice to relieve the sensation.

Shivering or Chills

Shivering or chills is a common reaction to the medication given during surgery and typically resolves when the medication wears off. It can also be caused by a small drop in body temperature during surgery. This can be resolved by covering up with a few extra blankets until the chills pass.

A fever can also cause chills and shivering but is a less common cause immediately following the surgery unless an infection was present prior to the procedure.


The medication used for general anesthesia can cause drowsiness and many individuals doze on and off in the hours following surgery. Typically, after a good night of sleep, you will likely feel more like yourself.​

Muscle Aches

Paralytic medications used commonly with general anesthesia are known to cause muscle aches. Lying completely still in one position during surgery can also cause soreness. Patients often complain of body pain after a procedure, typically back pain, caused by being unable to shift positions during surgery.


The medications given during and after surgery can, and often do, result in itching. 

Serious Issues

You will have frequent postoperative checks for the first few hours after surgery. If you are showing signs of a serious complication during your recovery, you may need immediate treatment.


You can have an altered mental status after surgery, with symptoms of confusion or agitation. This is especially common in individuals who are elderly or who have Alzheimer’s disease or other types of dementia or cognitive problems.

The combination of anesthetic medications with underlying cognitive issues normally often leads to an increase in confusion until the body completely clears the anesthesia. The change from the home environment to an unfamiliar one (hospital, surgical center) can worsen confusion.

Being in an intensive care unit (ICU) is a known risk factor for both delirium and worsening of confusion, as the patient is constantly being stimulated with lights at all hours of the day and night, sounds of machines beeping and alarming, and the constant necessary medical interventions by staff.

​Difficulty Urinating

General anesthesia paralyzes the bladder muscles. Additionally, many surgeries involve the placement of a Foley catheter (urinary catheter) to collect urine during the procedure.

After a urinary catheter is removed, it can be difficult to adequately urinate in the following days.

Irritation, which is common after having a Foley in place, can lead to burning while urinating. This does not necessarily mean that a urinary tract infection (UTI) is present.

While a urinary tract infection is more likely after having a Foley placed for surgery, most patients do not experience any ill effects from having a catheter. In rare cases, a patient cannot urinate after having surgery, and this requires immediate medical attention.


Just as the function of the bladder can be affected by anesthetic medications, so can the function of the intestines. When the intestines don’t resume normal function within one to three days after surgery, it is referred to as an ileus. This problem typically resolves within four to five days following surgery.

During same-day surgery, the patient is often kept in the recovery room until they begin to pass gas, a sign that they do not have an ileus and can safely go home.

Difficulty Getting Off the Ventilator

For most patients, the breathing tube is removed as soon as surgery is completed and they are able to breathe on their own. This happens within minutes of the completion of the procedure. Other patients—often older or sicker patients—require more time to be taken off the ventilator successfully.

Patients who cannot be safely taken off of the ventilator immediately after surgery can often do so after a few hours. In rare cases, a patient may require an extended stay in an intensive care area while the healthcare team works to get the patient breathing independently.

Aspiration and Aspiration Pneumonia

This is a potentially serious issue that occurs when saliva, food, or fluid is accidentally inhaled into the lungs during surgery.

During normal day-to-day life, we call this “going down the wrong pipe” and we cough it up. During surgery, it isn’t possible to cough or even be aware that something is going down the wrong pipe.

This is why you would be instructed to fast from eating or drinking for a specified number of hours before your surgery—undigested material in your stomach can come back up from your stomach and into your lungs due to anesthesia-induced weakness of the gastroesophageal sphincter that normally keeps food from coming back up out of your stomach. Fasting reduces the chances of having food or fluid in your stomach.

Unconsciousness during general anesthesia makes a person unable to protect their own airway with reflexes such as gagging and coughing—so saliva or vomit can mistakenly enter the lungs.

This can lead to pneumonia after surgery, which is considered a serious complication that requires antibiotic therapy and can lead to readmission to the hospital in some cases.

Blood Clots

Being in the same position for several hours during surgery can increase the risk of forming a blood clot, known as a deep vein thrombosis (DVT), after surgery. These clots most often happen in the extremities, particularly in the legs.

If you have ever had surgery and wondered why the staff wanted you up and walking so soon after your surgery was completed, it was to prevent blood clots from forming.

Malignant Hyperthermia

This is an extremely serious condition that's caused by a genetic, inherited tendency to react to some medications used during anesthesia. It can be life-threatening. The condition causes a high fever and muscle contractions that can lead to organ failure if not diagnosed and treated quickly.

A patient who has a family history of malignant hyperthermia can be tested prior to receiving anesthetics with a blood test that can identify the gene.

Anesthesia Awareness

This is a rare condition that occurs when anesthesia is not effective for inducing unconsciousness. Patients report experiences ranging from remembering parts of conversations being held in the operating room during their procedure to being able to see, hear, and feel everything that happens during surgery.

Anesthesia awareness is not common when appropriate anesthesia is given during the procedure.

A Word From Verywell

Anesthesia involves a careful analysis of dosing, timing, and risks of the medication. Your anesthesia team is required to have had years of training and experience. They normally take steps to minimize the chances of the problems and increase the likelihood of good outcomes.

Serious complications after surgery need to be evaluated and treated promptly. If you believe you are having a serious or potentially life-threatening complication, call for professional help or go to the emergency room immediately.

Minor issues such as itching or nausea will not warrant a middle-of-the-night trip to the ER, but an inability to urinate, difficulty breathing, or severe swelling, bleeding, or pain should be addressed without delay.

Frequently Asked Questions

  • How long does it take for general anesthesia medicines to be eliminated from the body?

    Around 24 hours—which is why it's advisable to not drive, try to work, or do any other activity that requires your full attention for at least a day after receiving general anesthesia.

  • Why do I still feel groggy days after having general anesthesia?

    It may have less to do with the anesthesia than with the energy your body is using to heal from whatever procedure you had, the post-operative pain medications you're taking, or jumping back into your regular activities too soon.

  • Is there any way to speed up recovery from general anesthesia?

    There's some evidence caffeine might do the job. In studies, caffeine administered intravenously has had a number of positive effects on recovery from general anesthesia, such as returning breathing to normal.

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