The Side Effects and Complications of General Anesthesia

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

Man going under anesthesia
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Luckily, severe issues after receiving anesthesia are uncommon and the average patient will experience no issues or only minor ones in the hours and days following their procedure.

The type of side effects an individual undergoing anesthesia can experience can vary widely based on the individual's current health and history, the type of anesthesia they receive, the length of time they are under anesthesia and the nature of the procedure for which they are undergoing anesthesia.

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

General Anesthesia Explained

This type of anesthesia is used during surgeries and is used in a hospital or surgical center setting. Medication is given both as an inhaled gas and through an IV 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 much deeper than sleep.

General anesthesia requires the patient to have a breathing tube placed so they can be on a ventilator during surgery. This is because general anesthesia medications do not just make the patient unconscious and unable to feel the pain of surgery, they also paralyze the muscles of the body including the muscles that make the lungs work.

While the general anesthesia medications cause paralysis that keeps the patient from moving—which is particularly important during delicate surgeries—this can also lead to complications caused by not moving for an extended period of time.

Anesthesia, involves a careful analysis of potential risks versus potential benefits, and years of training and experience guiding which one outweighs the other. Actions are also taken to minimize the chances of the problems and increase the likelihood of good outcomes.

It is important to remember that the risks of general anesthesia are not the only risks the patient should be aware of prior to their procedure, the risks of the surgery itself must be considered. Every procedure carries its own unique potential risk factors, unrelated to the anesthesia.

For example, a patient having surgery to remove the appendix would have risk factors related to the infection that is present in the appendix potentially spreading into the abdomen during surgery, as well as the potential for an infection in the incision, which is unrelated to the risks of general anesthesia.

Common Issues

These problems are the most frequently seen after general anesthesia.

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, and multiple medications are available for patients who experience this issue.

The best predictor of whether or not a patient 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 to prevent it from happening again.

Sore Throat or Hoarseness

After having the breathing tube placed, a sore throat or a hoarse voice can be expected, particularly if the 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 after 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 a result of some of the medications used.

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, an issue that is easily resolved by covering up with a few extra blankets until the cold chills pass.

The presence of 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, patients indicate they feel more like themselves.​

Muscle Aches

One of the medications used commonly with general anesthesia is known to cause muscle aches. Lying completely still in one position during surgery can also cause muscle aches. 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

There are several problems of a serious nature that can arise after general anesthesia. Some require immediate medical attention.


Alterations in mental status, particularly in those who are easily confused prior to surgery, are sometimes seen after surgery. This is especially common in individuals who are elderly, have dementia, Alzheimer’s disease, or other conditions that make confusion likely.

The combination of medications and a tendency to be confused normally often lead to an increase in symptoms until the body completely clears the anesthesia. The change from the home environment to an unfamiliar one (hospital, surgical center) can worsen confusion.

If care is being provided in the ICU, this 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 constant (necessary) medical interventions by staff.

​Difficulty Urinating

General anesthesia paralyzes the muscles of the body, and the bladder is made of muscles and is surrounded by muscles that allow it to work. Not only can the medication affect the bladder, but many surgeries require the placement of a urinary catheter.

The removal of the urinary catheter, commonly known as a foley catheter, can interfere with the ability to urinate in the days following. Irritation is common after having a foley placed, which can lead to burning when urinating, which does not necessarily mean there is a urinary tract infection (UTI) 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 the 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 medications so can the function of the intestines, and when the intestines don’t wake up in a reasonable period of time it is referred to as an ileus. This problem typically resolves in the days immediately 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 within minutes of the completion of their procedure. Other patients, often older or sicker patient, 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 to wake more from the medications. In rare cases, the patient will 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 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 whatever it is up. During surgery, it isn’t possible to cough, or even be aware that something is going down the wrong pipe, which leads to saliva or even vomit going into the lungs. Because the patient is not conscious during general anesthesia and is not able to protect their own airway with reflexes such as gagging and coughing, it is possible that foreign substances can 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, 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 is a genetic, inherited reaction 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 relative with a history of malignant hyperthermia can be tested prior to receiving anesthetics.

Anesthesia Awareness

This is a rare condition that results from anesthesia not being fully effective in causing 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.

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

A Word From Verywell

Serious complications after surgery will never be improved by waiting to seek treatment. If you believe you are having a serious or potentially life-threatening complication, waiting until the morning to go to the emergency room is not going to help, but could dramatically worsen the situation.

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 other issues should be addressed without delay.

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