Having surgery? Use marijuana? Be sure to let your doctor know.

Marijuana users may require 10 times more anesthesia than a non-user to stay “asleep’’ during surgery
April 18, 2023
Dr. Jennifer Kollman is an expert on anesthesia and use of marijuana or weed. Photo by Erin Emery.
Anesthesiologist, Dr. Jennifer Kollman, describes how it may be more challenging to properly sedate patients who use marijuana or weed. Photos by Erin Emery.

If you’re having surgery and a doctor asks if you use a marijuana product, be honest.

Using marijuana – smoking, vaping, eating edibles or using tincture – can affect how anesthesia works. Providing accurate information about marijuana use will help your anesthesiologist make sure you stay “asleep’’ for the duration of the surgery.

Chronic users – those who use marijuana at least once a week – may require more anesthesia than those who do not use marijuana or opioids.

“It’s extremely important that patients are honest with us,’’ said Dr. Jennifer Kollman, an anesthesiologist and senior medical director for anesthesia at UCHealth in southern Colorado. “We can figure it out once you are asleep, but it is best if we don’t have to. There are some increased risks with recent marijuana use and continuous long-term marijuana use.’’

The risks of complications with anesthesia and marijuana use include the following:

  • It may take longer for recent or chronic users of marijuana to empty the contents of their stomach. During surgery, you may be more prone to having stomach contents come into your throat and sucked into your lungs before an anesthesiologist can insert a breathing tube.
  • If you have pre-existing heart disease, there is a risk of heart attack if you use marijuana within 60 minutes of receiving anesthesia. “We want to know so we can be super vigilant about that,’’ Kollman said.

UCHealth Today asked Kollman to discuss how important it is for a person who uses marijuana to let their anesthesiologist know before surgery.

Why should you be honest?

There are quite a few things that can happen, though if a patient doesn’t let us know that they use marijuana, we can usually figure it out once they are asleep. Their body will tell us, and their level of consciousness will tell us. If I was to use an anesthetic on someone who was a regular cannabis user, I might need 100 milliliters of Propofol to keep them asleep, whereas a non-cannabis user would require 10 milliliters.

“So it can take me 10 times more to get someone to fall asleep depending upon their use and when they last used,’’ Kollman said.

Why is more anesthesia required to keep a person asleep?

Dr. Jennifer Kollman is an expert on anesthesia and use of marijuana or weed. Photo by Erin Emery.
Anesthesiologist, Dr. Jennifer Kollman, describes how use of marijuana or weed can affect people during surgeries.

We have receptors in our body that are cannabinoid receptors, and we naturally make some cannabinoid substances. When we use extra marijuana or CBD, then we fill those receptors up. Cannabinoid receptors can also cross-react with opioid receptors, so people don’t respond well to normal pain medications. They won’t respond well to opioids and other pain-management medications that we use.

We also have to consider how we will control their pain after surgery. Sometimes that means using other types of medications to control pain or non-medicinal approaches to treating pain.

How often do I have to smoke weed to affect anesthesia during surgery?

Using marijuana once a week affects the receptors in the body and basically saturates those receptors, so they cross over to the opioid receptors so that the opiate medicines don’t work very well. According to the American Society of Regional Anesthesia and Pain Medicine (ASRA), chronic use is listed as once per week and over an extended period of time.

Since marijuana is legal in Colorado, are people reluctant to admit their use of marijuana?

We asked patients about their marijuana use long before marijuana was legalized in Colorado because most anesthesiologists have experienced that it takes a lot more anesthesia to keep some patients asleep, which tends to correlate with cannabis use.

What has changed is that people are a little more willing to let us know and to be honest about it. I’ve always told people that I really don’t care what they use. What I care about is taking good care of them.

If they let me know what they have been using and how much, I can adjust the medications to ensure they have the best experience possible.

How do you monitor the quality of a patient’s sedation during surgery?

We use a person’s body type and body weight to get a rough estimate of doses of anesthesia that will be needed. And we can also take into account their different physiology, their organ systems and what type of surgery they are going to have.

Beyond that, we use their vital signs, for instance, their heart rate. Is it too fast or too slow? What’s their blood pressure doing? The body really tells us what it needs. When we think that somebody has ingested a mind-altering substance, we monitor brain waves to tell us exactly where that person is in terms of consciousness.

Many people have a fear of waking up during surgery. How do you prevent that from happening?

There are only two big reasons why someone might wake up from the anesthetic when they are not planning for it. No. 1 is they are so sick, they are so ill, that if you gave them a full general anesthetic, it would kill them. In that case, we hear reports that people are hearing things, but they rarely report any pain. The other instance is when you have bypass surgery, and we are rewarming the body to get the heart ready to start working on its own again, and again, it is usually a time when people report that they are hearing things.

With marijuana use, we’ll generally figure it out by what it initially takes to get people to sleep and what their vital signs are.

How long does it take for anesthesia to take effect?

Everything that I give takes less than 30 seconds to work, which is one of the reasons I love my job.

Anesthesia and marijuana. People who use marijuana or weed should let their doctors know before they have surgery. Photo by Erin Emery.
Anesthesia and marijuana. People who use marijuana or weed should let their doctors know before they have surgery. Dr. Jennifer Kollman shows Propofol and how much more medicine may be needed to keep a person who uses marijuana “asleep” during surgery.

What do you ask patients when inquiring about marijuana use?

I make it a habit to ask, ‘Do you use any marijuana products?’ And I specifically say products because I want to know if it is something that you are smoking, vaping, an edible or tincture. All of that can have different effects on the body for different lengths of time. The next thing that I would want to know is, ‘How long ago did you last use it?’ Because, again, within certain amounts of time, there are different effects on the body, and I want to be aware of that.

After that, we want to know: How often do you use it? Did you use it last week? Do you use it daily? Have you used it in the last month? That’s going to also affect what we need to do and monitor.

Are there other substances that also affect anesthesia?

Yes, there are uppers and downers, suppressants, and depressants and stimulants. All of them have different effects on the body. The definition of a drug is a “substance that affects the body,’’ so it doesn’t matter if it occurs naturally or is made in a lab, every drug can have a cross-reaction to anesthesia.

We need to know what those substances are so that No. 1, we don’t harm you, and No. 2, we don’t give you a bad experience.

How do you reassure someone who may be uncomfortable revealing their use of substances?

We want to do our best to take care of the patient. We will not turn people into the cops, that’s not our job. Our job is to be the best doctor that we can for that one person at that one time. So, be very honest with us because all we will do with that information is make the experience better for you.

Are there other reasons that doctors should know about a patient’s marijuana use?

Yes. We worry that after surgery, people who are in the hospital may experience marijuana withdrawal. We want to be considerate of ‘how do we take care of those patients when they’re going through withdrawal symptoms?’

This could include tachycardia, an increased heart rate; irritability; oppressiveness; and sometimes, a lot of nausea. These things can easily be mistaken as symptoms of other problems, so if we don’t know specifically to look for cannabis withdrawal, then we may miss it.

Is there a difference between smoking marijuana or using CBD? What’s the difference between different types of marijuana products?

CBD doesn’t tend to have the same effects as THC – it can have a more sedative effect on people. However, in a recent study, 21% of CBD products that were labeled as pure CBD   still had a significant amount of THC in them. So, it is hard to know what you are actually ingesting.

Does marijuana affect pregnant women?

A lot of people may not realize that even though marijuana is a natural plant, it has effects on pregnant women and their babies. It crosses the placental barrier, so the baby gets about 10% of the marijuana that the mother takes. It leads to a lot of underweight babies that are born prematurely, and it has also been shown that there are some brain alterations that may be involved.

Children who are born after the mother has been using marijuana tend to have changes in their frontal lobe, which affects executive function and risk-taking behavior.

Can someone be such a heavy marijuana user that you can’t put them under?

No, we can always put someone under using anesthesia.

About the author

Erin Emery is editor of UCHealth Today, a hub for medical news, inspiring patient stories and tips for healthy living. Erin spent years as a reporter for The Denver Post, Colorado Springs Gazette and Colorado Springs Sun. She was part of a team of Denver Post reporters who won the 2000 Pulitzer Prize for breaking news reporting.

Erin joined UCHealth in 2008, and she is awed by the strength of patients and their stories.