- Anesthesia prevents pain during procedures by numbing you or putting you into a sleep-like state.
- Though considered very safe, it can cause side effects like nausea, chills, aches, and sleepiness.
- Rarely, it may lead to serious complications, but your doctor can offer tips to lower your risk.
Anesthesia is a drug administered before certain medical procedures, surgeries, and tests.
The two most common types of anesthesia include:
- General anesthesia, administered intravenously or through a breathing mask or tube, puts you in a sleep-like state where you don't feel any pain. This is the default for major, invasive operations.
- Local anesthesia, administered via a single injection for less-invasive procedures or tests, numbs a specific area of the body. You won't feel pain, but you'll remain awake and alert.
Anesthesia is considered very safe for most people, says Dr. Taylor Graber, a physician anesthesiologist and owner of ASAP IVs. That said, it can cause some side effects, such as nausea, sore throat, and sleepiness. Rare complications may include awareness during the procedure, nerve damage, or intestinal issues.
Here's what to know about the possible side effects and complications of anesthesia — plus the risk factors for these effects.
What does anesthesia do?
Anesthesia makes you more comfortable during medical procedures by temporarily blocking the pain signals your nerves send to your brain. It also helps keep you still so the doctor or surgeon has an easier time performing the procedure without any issues.
You'll likely get anesthesia when undergoing any kind of medical or surgical procedure, according to Dr. Jordan Frey, a plastic surgeon at Erie County Medical Center and founder of The Prudent Plastic Surgeon.
Whether you get local or general anesthesia will likely depend on the type of procedure:
- Local anesthesia: Used for simple procedures like a wisdom tooth extraction or mole removal. This is administered by the doctor, dentist, or surgeon performing the procedure.
- General anesthesia: Used for complex procedures like open-heart surgery, gallbladder removal surgery, and knee or hip replacements. General anesthesia must be administered by an anesthesiologist.
Graber says general anesthesia may also be used in cases where someone has extreme anxiety about a specific procedure — sedation can help the doctor or surgeon perform the procedure safely.
Side effects
General anesthesia is more likely to cause side effects than local anesthesia. However, it's very safe and generally well-tolerated. Frey says the majority of side effects are minor and last no more than a couple of hours.
According to Graber, the most common side effect of general anesthesia is postoperative nausea and vomiting (PONV).
Nausea and vomiting may set in anywhere from the first hour after you wake up to a couple of days later. But it generally doesn't last long, and anti-nausea medications can offer relief. You're more likely to experience PONV if you're:
- Female
- A nonsmoker
- Under the age of 50
- Have a history of motion sickness or vomiting after surgery
While PONV usually goes away after an hour or two, in rare cases the nausea can last up to 48 hours.
Other common side effects of general anesthesia include:
- Shivering or chills: About half of patients experience this second-most-common side effect after waking from anesthesia. It happens as a result of the slight drop in body temperature caused by general anesthesia.
- Sore throat or hoarseness: These side effects, usually caused by the breathing tube used while you're unconscious, can be treated with throat lozenges, Frey says. The longer the duration of your surgery, the greater your chances of having a sore throat and hoarseness.
- Muscle aches: You may experience these as a result of the medications administered to relax your muscles before inserting a breathing tube, or from lying still during the procedure without the ability to shift positions.
- Sleepiness or fatigue: The severity of this can depend on the strength of the medications used in the anesthetic, Graber says.
- Confusion or disorientation: Older adults and people with cognitive decline, like dementia or Alzheimer's, may be more prone to this side effect, which can come and go for up to a week.
- Itching: This side effect usually occurs if you receive any opioid medications during or after your procedure. The itching sensation is typically felt on the torso, and around the nose and eyes.
- Difficulty urinating: This less-common side effect may occur because anesthesia paralyzes the bladder muscles, Frey says. It's more common if you have a history of urinary difficulties. It usually passes on its own, but you may temporarily need to use a urinary catheter.
Potential complications
Older adults and people with serious health conditions are more likely to experience complications, Graber says. That said, complications are not common.
A 2019 study of patients who received general anesthesia before surgery found that complications only happened in about 3% of cases. Most of those were mild — severe anesthesia-related complications only happened in .003% of cases.
Potential complications include:
- Aspiration: This happens when you accidentally inhale regurgitated liquids or food from your stomach, and can't clear your lungs because you're unconscious. It only occurs in 1 in every 2,000–3,000 operations requiring anesthesia
Following your doctor's preoperative fasting guidelines can greatly lower your risk of aspiration. - Malignant hyperthermia: A severe reaction to certain anesthesia drugs known as malignant hyperthermia can lead to organ failure if not treated promptly. Frey advises letting your doctor know if you or a family member has a history of malignant hyperthermia. A blood test can identify if you have the gene that increases your risk.
- Intestinal problems: Anesthesia medications can sometimes cause ileus, a condition where the intestines can't move food and waste through your digestive tract properly. It can involve bloating and constipation that typically goes away within three to five days. Treatment usually includes IV fluids and electrolytes.
- Atelectasis: General anesthesia alters your breathing pattern, which can cause atelectasis, where the air sacs in your lungs deflate. Smokers and those with asthma or another lung disease are at higher risk, but you can lower your risk with deep breathing exercises post-procedure. If symptoms don't resolve within 24 hours, contact your doctor for treatment.
- Postoperative delirium: Postoperative delirium (POD), or confusion that comes and goes, can set in minutes after anesthesia is administered or days after the procedure. Those over 60, who use alcohol or drugs heavily, or who have pre-existing psychiatric conditions are at higher risk. POD typically lasts less than a week, and visiting with family and friends can help.
Factors that increase your risk of anesthesia side effects or complications
Any medical condition that impacts your overall health, especially heart and lung health, will increase your risk of side effects or complications, Frey says. These conditions include:
- Heart, kidney, or lung conditions
- High blood pressure
- Medication allergies
- Alcohol use disorder
- Diabetes
- Obesity
- Obstructive sleep apnea
- Seizures
Smoking, or taking aspirin and other medications that increase bleeding can also increase your risk of side effects.
Can you reduce your risk of experiencing anesthesia side effects?
Dr. P. Daniel Ward, a double-board certified facial plastic surgeon in private practice, says maintaining a healthy lifestyle is the single best way to minimize your risk of anesthesia side effects and complications. He also recommends closely following your doctor's pre-surgery instructions, which may include:
- Fasting
- Avoiding alcohol and drugs beforehand
- Scheduling someone to take you home afterward
In addition to clarifying anything you're unsure about, Frey says your care team may be able to prescribe pre-medications to help minimize the risk of certain side effects like nausea and vomiting.
"You are fully entitled to ask what the plan is for anesthesia," Graber says.
"If you have any risk factors for complications, you may also ask how these are going to be monitored. You are your best advocate to ask if alternate anesthesia approaches can be used, such as the use of nerve blocks or regional anesthesia to reduce intraoperative and postoperative pain," Graber says.
Insider's takeaway
On the whole, anesthesia is very safe. Even when it does cause side effects or complications, they're typically mild and short-lived.
You have a higher risk of side effects or complications if you're an older adult or have pre-existing medical conditions, especially those that affect the heart and lungs. The best way to reduce your risk of complications involves following all pre-surgery instructions.
If you're worried about the potential side effects or complications of anesthesia, don't hesitate to share your concerns with your doctor or surgeon. They can answer your questions, provide more information on what to expect, and offer guidance on lowering your risk of side effects and complications.