Colonoscopy Anesthesia: Types, Levels, and Possible Side Effects

Undergoing a colonoscopy can be a nerve-wracking affair. It’s common knowledge that colonoscopies can be uncomfortable, especially for first-timers. This makes a lot of people averse to getting screened, even though they are at high-risk for colon cancer.

In reality, not all colonoscopies have to be uncomfortable. Your level and type of sedation or anesthesia is an important choice to make, and can define your colonoscopy experience, the recovery, and side effects afterwards. Understanding the specifics of anesthesia for colonoscopy is crucial towards making the right choice for yourself.

What is a Colonoscopy?

A colonoscopy is a medical procedure that involves a colonoscope, a medical device that consists of a small camera and light mounted on a thin, flexible tube. The tube is inserted into the patient’s rectum and pushed up into the large intestine, also known as the colon.

The procedure is invasive in nature. In some cases, doctors introduce air into the colon to gently inflate it, allowing them to see better. Patients may experience discomfort after the exam because of this.

The minor inconvenience posed by colonoscopies is mitigated when its benefits are considered. This procedure can save a patient’s life by effectively detecting and removing polyps, which increases your chances of preventing or even surviving colon cancer.

Why Do Patients Need a Colonoscopy?

Patients are recommended to get a colonoscopy if they are experiencing symptoms such as:

  • Blood coming from the anus
  • Unusual and extreme bowel activity changes
  • Unexplained sudden weight loss
  • Chronic abdominal pain

These symptoms can be signs of colon and colorectal cancer, which can develop in patients who have some or all of the following risk factors:

  • Male
  • A family history of polyps or colon cancer
  • African American
  • Have a history of digestive conditions, such as inflammatory bowel disease
  • Obese
  • Cigarette smoker
  • 50 years of age or older

While many people associate colon cancer with patients 50 years and above, colon cancer can actually develop at any age. If doctors observe symptoms similar to those listed above, you may be recommended for a colonoscopy regardless of your age (source).

Colonoscopy and Anesthesia: Everything You Need To Know

As a patient, you have the right to decide on the level of sedation and the type of anesthesia for your colonoscopy, so it is important for you to understand the varying levels of colonoscopy sedation and what anesthesia colonoscopy can do to your body.

Levels of Colonoscopy Sedation

Firstly, it is important to be aware of the different levels of sedation that you can be under while undergoing a colonoscopy.

  • No Sedation: No medications or anesthesia is used in these cases. A very small number of patients choose to have zero sedation during a colonoscopy.
  • Light: Light sedation is enough to make a patient slightly sleepy, however, you should experience no changes to your motor functions, your cardiovascular function, or your general breathing. Patients under light sedation are mostly conscious, and can feel some levels of pain and respond to questions.
  • Moderate: Also known as Conscious Sedation, moderate sedation is slightly more powerful than light sedation. The patient should still have the consciousness to feel physical stimulation and respond to doctors verbally.
    There is a very low risk of any interference with the body’s cardiovascular function. However, one noteworthy effect is the lack of memory: patients under moderate sedation generally have little to no memory of it.
  • Deep: Patients under deep sedation will have zero recollection of the procedure. This is riskier for patients who might have breathing or cardiovascular problems, as there is a risk of breathing being impaired while under deep sedation.
  • General Anesthesia: It is very rare for a patient to go under general anesthesia for a colonoscopy, however it can happen under special circumstances or if requested. Patients will have no painful sensations during general anesthesia, however a tube will be placed over their lungs to assist with breathing.

Many patients generally ask to be unconscious for a colonoscopy, but after they are informed of the potential risks of general anesthesia, patients generally opt for a lower level of sedation instead.

Sedation Levels: Which to Choose?

a nurse preparing anesthesia injection

Every level of sedation has its own set of advantages and disadvantages. Here are the different experiences you may undergo with each level of sedation:

No Sedation – Best For No Downtime: While not many patients choose to undergo a colonoscopy without any sedation, patients who do choose this path have the quickest recovery after the procedure. They have very little recovery time and can operate at normal levels immediately afterwards.

They also do not have to worry about possible anesthesia-related complications. If you decide to undergo a no sedation colonoscopy, discuss this possibility with your doctor and make sure that they have done unsedated colonoscopies in the past.

Light Sedation – Not Recommended: A rare choice of sedation level, as it carries the risk of anesthesia complications without offering many of the benefits of sedation. Patients will not be able to participate in daily activities until at least the day after their procedure.

Moderate Sedation – Reliable Choice: The most common sedation level with the colonoscopy procedure. Here, patients are generally given fentanyl (a pain killer) and midazolam (a sedative, mild). To make sure that the patient has the right amount of sedation, a nurse and doctor should monitor the patient during the entire procedure and sedation duration.

Deep Sedation – Requires Anesthesiologist: Deep sedation can also be referred to as MAC, or Monitored Anesthesia Care. Propofol is the top choice of sedation for this sedation level, and it is administered by an anesthesiologist as well as your doctor and nurse.

General Anesthesia – Rare: Very rarely used for colonoscopy, and is only recommended for patients who have issues with their lungs or will experience longer examinations.

The Colonoscopy Patient Anesthesia Experience

Your experience of anesthesia and sedation during a colonoscopy will depend on the type of anesthesia you choose, however you can expect a general experience if you choose moderate sedation or deep sedation, in which an anesthesiologist is present.

Prior to your procedure, your doctor should prepare you with instructions for the days leading up to your colonoscopy. These are meant to make sure that your colon is empty. For anesthesia, it is best that a patient avoids drinking clear liquids for two hours before the examination, and avoids eating any food for eight hours before it.

When you come in for your colonoscopy, a nurse and an anesthesiologist will discuss with you your vital signs, medical history, and any potential problems you might have with the anesthesia. If you have serious potential problems, you will be recommended to take conscious sedation instead of heavier sedation levels.

Patients with no problems with their blood pressure or heart will have an intravenous drip attached to their arm. In about five minutes, the patient should be unconscious from the anesthesia. Patients are generally surprised to wake up later and find out that the procedure is done.

Possible Side Effects of Colonoscopy Anesthesia

Anesthesia with colonoscopy has become a topic for debate in the medical community due to the possible side effects, risks, and complications experienced by patients even at the conscious sedation levels. These side effects include:

Respiratory Depression

Respiratory depression is the condition that occurs when a patient experiences fewer than 12 breaths every minute. Their breaths become ineffective, slow, and shallow, due to the strength of the sedative in slowing down the brain signals that deal with breathing. The mild anesthesia popular with colonoscopy examinations has been found to occasionally affect the respiratory drive.


Bradycardia, or slow heart rate, can be caused by the effects of anesthesia on the autonomic nervous system. The autonomic nervous system (ANS) is responsible for body functions such as the heart rate, and bradycardia can be potentially dangerous to some patients with weaker hearts.


Hypotension, or low blood pressure, leads to dizziness, fatigue, and overall feelings of exhaustion. Anesthesia in colonoscopies has been found to lead to hypotension, which is why anesthesiologists should first check patients who regularly take medication for their blood pressure.

Vomiting, Nausea

Vomiting and nausea are common side effects of pain relievers and sedatives. This is why patients are prohibited from eating or drinking for several hours prior to a colonoscopy.

Colonoscopy With Anesthesia: Is It Necessary?

question mark

More patients are considering alternative options before undergoing a full anesthesia for a colonoscopy. Is full anesthesia right for you, with costs, pain, and alternative treatment options considered?

1) Anesthesiologists Might Not Be Covered By Insurance

The costs associated with anesthesia can sometimes be much more than most patients would expect. The main issue is that anesthesiologists are often not covered by general health insurance plans, meaning patients have to pay out of pocket for a simple anesthetic.

Some gastroenterologists also recommend that patients undergo full anesthesia for a colonoscopy, however, there is little scientific evidence showing that it is necessary. In many cases, patients might prefer to forego anesthesia altogether after finding out how much it will cost (source).

2) Not As Painful As You Might Think

Many studies have found that the pain of an unsedated colonoscopy is actually within the pain threshold of most patients (source). While the sensation may be an unusual and uncomfortable sensation, a majority of patients studied by researchers claimed that they would undergo the procedure without sedation again.

3) Alternative Tests

For patients who are adamant against the colonoscopy procedure and dealing with anesthesia, there are a few alternative tests they may consider. The best alternatives to colonoscopy include:

  • Fecal occult blood test (FOBT): The FOBT is a test that inspects an individual’s stool samples. The doctors search for any signs of hidden or occult blood, which could potentially indicate a presence of polyps in the rectum or colon, or colon cancer itself. For more details, read our post: Your Blood Can Tell If You Have Colon Cancer
  • Virtual colonoscopy: Also known as computerized tomography colonography, a virtual colonoscopy involves x-ray machinery to create a visualization of a patient’s colon and rectum, allowing doctors to search for any polyps and other signs of cancer. Virtual colonoscopies are also used when doctors believe that a colonoscopy was incomplete or ineffective, and seek more information on the patient’s colon.

While alternative tests can be easier on the patient, note that they are not as effective as colonoscopy. Additionally, alternative tests may be able to identify and locate polyps and colon cancer, but a colonoscopy will still be necessary afterwards for the actual removal.

FAQ – Colonoscopy and Anesthesia

What kind of anesthesia is used for colonoscopy? Is colonoscopy done under general anesthesia?

This depends on the type of anesthesia or sedation level the patient chooses. Generally, the sedative agents for colonoscopy include Propofol, midazolam, and fentanyl.

How long does colonoscopy anesthesia last?

After a colonoscopy, a patient can expect to stay at the hospital or a recovery room for up to two hours after the examination. However, a patient will not be fully recovered from the anesthesia until up to 48 hours after the procedure.

How painful is a colonoscopy without sedation?

While many patients are fearful of the idea of undergoing a colonoscopy without sedation, several studies have found that it isn’t as painful as many believe. In one study, 73% of patients who were given an unsedated colonoscopy were willing to do it again (source).

How long does a colonoscopy with anesthesia take?

The entire colonoscopy procedure should take anywhere from 30 minutes to an hour.

Why is an anesthesiologist necessary for anesthesia?

When dealing with Propofol, the main sedative for colonoscopy anesthesia, the Food and Drug Administration has made it a requirement that a nurse anesthetist or anesthesiologist must be present during drug administration. This is because Propofol can lead to apnea and other side effects.

Learn More About Colonoscopy Anesthesia

For individuals interested in learning more about colonoscopies, anesthesia, and safe and proper anesthesia practices, feel free to contact us at the Gastro Center in New Jersey. We are always ready to assist patients in understanding more about their needs and concerns.

Contact us today and learn about how we can help you and your upcoming colonoscopy.