The Side Effects and Complications of General Anesthesia

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Side effects and complications of general anesthesia—medications that render you immobile and unconscious for a medical procedure—vary widely.

You may experience minor issues like nausea or dry mouth, or something more serious like confusion or difficulty urinating. General anesthesia also poses a risk of life-threatening issues such as a condition that can lead to organ failure.

Man going under anesthesia
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Thankfully, most people have no issues or only minor ones in the hours and days following their surgery. While severe reactions are rare, they do occur. Some people are at greater risk for side effects of general anesthesia than others.

This article explains how general anesthesia affects your body, common side effects of anesthesia, and serious problems that could occur. It also explains how side effects and complications are managed or treated.  

How Anesthesia Affects Your Body

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 (into the vein) before and during surgery.

When you're "put to sleep" in this way, you actually enter a state of consciousness that's much deeper than normal sleep. You become completely unaware of your surroundings and don't feel pain.

The muscles of your body are temporarily paralyzed by the medication so that you stay perfectly still during your procedure.

Since the muscles you use to breathe are included in this, a breathing tube is inserted into your throat and hooked up to a machine that will breathe for you (ventilator) while you are under anesthesia.

Recap

Anesthesia temporarily paralyzes your body so your doctor can perform surgery without muscle movements getting in the way. A ventilator is used to help you breathe while you are under.

Common Side Effects of General Anesthesia

Your doctor and the surgical team should be able to help prevent side effects with medication or proper care before and during surgery.

They'll also monitor you for signs of problems and treat them (if they occur) after your procedure. When side effects do occur, they usually go away in a few hours.

Nausea and Vomiting

The most common complications after general anesthesia are nausea and vomiting. You're more likely to experience postoperative nausea and vomiting (PONV) if you have a history of nausea and vomiting after previous surgery.

Anti-nausea medication can usually be given before surgery to prevent PONV. Medications can also be used to treat nausea when it does happen.

Sore Throat or Hoarseness

The breathing tube may leave you with a sore throat or a hoarse voice. The longer the surgery, the more likely this is to occur.

While throat problems usually can't be prevented, sore throat sprays, lozenges, and other medications can reduce throat pain in the days immediately after surgery.

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

Dry Mouth

Dry mouth can be a caused by a lack of food or drink both in the hours leading up to your procedure and during it.

It may also be due to the drying effect of anesthesia medications.

Dry mouth usually goes away within 24 hours after surgery. Meanwhile, you can use water or ice to relieve the discomfort.

Shivering or Chills

Certain medications that are given during surgery can cause shivering or chills. These symptoms typically resolve once the medication wears off.

Chills can also be the result of a small drop in body temperature during surgery. Covering up with extra blankets should help you get comfortable until the chills pass.

A fever can also cause chills and shivering. A fever immediately after surgery is more likely if you had an infection before the procedure.

Sleepiness

The medication used for general anesthesia can cause drowsiness. In fact, you may doze on and off in the hours following surgery.

After a good night of sleep, you should feel more like yourself.​

Muscle Aches

Paralytic medications—powerful muscle relaxants—used 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 the inability to shift positions during surgery.

Itching

The medications given during and after surgery can, and often do, leave your skin feeling itchy. 

Recap

The most common side effects related to anesthesia last for a short time. Nausea, sore throat, dry mouth, chills, sleepiness, achiness, and itching will usually disappear in a few hours or, in some instances, a few days. 

Serious Side Effects of General Anesthesia

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

Confusion

As you come out of anesthesia after surgery, you may experience an altered mental state due to the medication. Waking up in an unfamiliar setting like the hospital can contribute to confusion or agitation.

This is especially common in those who are of advanced age, have Alzheimer’s disease, or suffer from other types of dementia or cognitive problems.

The cognitive issues usually last until the anesthesia completely clears the body.

Being in an intensive care unit (ICU) is a known risk factor for both delirium and confusion because you're regularly stimulated by lights, beeping machines, and hospital staff.

Urination Problems

General anesthesia paralyzes the bladder muscles. This can make it not only hard to pee, but impact your ability to recognize you have to urinate altogether.

Additionally, many surgeries involve the placement of a Foley catheter—a tube put in the body to drain urine from the bladder. Both trouble urinating and urine leakage may occur in the days following its removal.

It's common also common to feel irritation and a burning sensation when you pee after having a catheter. This is sometimes mistaken for a urinary tract infection (UTI). While you are at risk for a UTI after having a Foley, most patients don't get one.

In rare cases, a patient cannot urinate after surgery at all. If this problem lasts for several hours, and you are no longer at the hospital or surgical center, seek immediate medical attention.

Intestinal Problems

Just as the function of the bladder can be affected by anesthetic medications, so can the function of the intestines.

In some cases, the intestines still can't properly move food and waste through the digestive system days after surgery. This is called an ileus.

Usually, this problem resolves within five days of surgery.

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

Difficulty Getting Off the Ventilator

The breathing tube is usually removed as soon as surgery is over and you're able to breathe on your own. For some older adults or people who have other medical conditions, the ventilator may be left in place for a few hours after surgery.

In rare cases, some may require an extended stay in an intensive care area while the healthcare team works to get the patient breathing independently.

Aspiration and Pneumonia

Aspiration is when saliva, food, or fluid is accidentally inhaled into the lungs during surgery.

When this happens in everyday life, you may call it "something going down the wrong pipe." The lungs are cleared after you cough the food or liquid back up.

But during surgery, you can't cough and aren't even aware that something's going down the wrong pipe.

This is a potentially serious problem. If undigested material goes into the lungs, it can lead to pneumonia.

To avoid this, you're required to fast from food and drink for a certain number of hours before surgery. If your stomach is empty, there's less chance of aspiration.

If you do end up with aspiration pneumonia, you'll need antibiotics and may need to be readmitted to the hospital.

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 legs.

The last thing you may feel like doing soon after surgery is getting up and walking around. However, your medical team will encourage it to prevent blood clots from forming.

Malignant Hyperthermia

This is extremely serious condition causes a high fever and muscle contractions that can lead to organ failure if not diagnosed and treated quickly.

Malignant hyperthermia is caused by an inherited tendency to react to certain anesthesia medications. It can be life-threatening.

If you have a family history of malignant hyperthermia, a blood test can identify if you carry the gene that puts you at risk.

Anesthesia Awareness

Anesthesia awareness is a rare condition that occurs when anesthesia doesn't make a person fully unconscious.

Patients report experiences ranging from remembering conversations held in the operating room during their surgery to being able to see, hear, and feel everything that happens during the procedure.

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

Recap

Difficulty urinating and passing food through the intestines may occur. In some instances, anesthesia may cause problems such as confusion and delays being able to breath without a ventilator. You will be asked to start walking ASAP after surgery to avoid blood clots.

Risk Factors

Side effects related to general anesthesia affect different people for different reasons. Whether or not you experience complications, and the severity of them, depend on factors such as:

  • Current health and medical history: For example, the risk increases if you have brain, heart, lung, or kidney disease.
  • Current lifestyle choices, such as smoking and abuse of drugs or alcohol
  • Family history: You may have problems if any of your family members are allergic to anesthetic medications.
  • What procedure you are having: The extent and duration of your procedure can impact your risk.
  • Medication given: There are several that can be used for general anesthesia.

For example, a child with no health issues who is given general anesthesia for an hour-long surgery to remove the tonsils will likely have fewer complications than an 85-year-old person who smokes and is under for several hours for open-heart surgery.

The risks of general anesthesia are not the only risks you need to be aware of before surgery. There are also risks of the surgery itself. With every procedure, there are possible problems that can occur that are unrelated to the anesthesia.

For example, a patient having surgery to remove the appendix may be at risk for an infection spreading from the appendix. There's also the risk of developing an infection at the incision.

Be sure to share as much detail about your health history and potential risk factors—whether you're sure it's relevant or not—with your healthcare team during your consultations leading up to your procedure.

This can help them sidestep potential issues ahead of time and put them on high alert for issues during and after your procedure, should you move ahead with it.

Recap

Whether or not you have complications after anesthesia is often related to your overall health. If you have other medical problems, are pre-disposed to anesthesia reactions, or smoke or abuse alcohol, you will be more likely to experience problems with anesthesia.

Summary

Serious complications related to anesthesia are rare. Minor side effects usually resolve quickly and do not warrant a middle-of-the-night trip to the ER. The most common problem, nausea, can often be prevented altogether with medication.

However, an inability to urinate; difficulty breathing; severe swelling; bleeding, or pain; or any signs of a serious complication need to be evaluated and treated promptly. Call for professional advice or go to the emergency room without delay.

Some people are more at risk for complications than others, including older adults and people with pre-existing conditions. Make sure you discuss your medical history and habits in full with your healthcare team before surgery so risk factors can be brought to light.

A Word From Verywell

Anesthesia involves a careful analysis of dosing, timing, and medication risks.

Your anesthesia team is required to have years of training and experience so they can make decisions that keep you safe. They are required to take strategic steps to minimize the chances of the problems and increase the likelihood of good outcomes.

This does not mean that side effects and complications won't occur, but it does mean that everything should be being done to avoid them.

Frequently Asked Questions

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

    Around 24 hours. That is why it's advisable not to 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. Grogginess may also be due to post-operative pain medications 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 given intravenously had a number of positive effects on recovery from general anesthesia, such as returning breathing to normal.

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10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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