Harvard Health Blog
Coming clean: Your anesthesiologist needs to know about marijuana use before surgery
Given the increasing prevalence and legalization of marijuana, many patients have come to think that marijuana use is not worth mentioning to their physicians. After all, they reason, I would not necessarily tell my doctor that I had a glass of wine last night, so why should I disclose that I smoked marijuana yesterday? Unfortunately, this reasoning is flawed. Because marijuana has a variety of effects on the body and on anesthesia medicines, it is crucial that anyone undergoing a preoperative evaluation disclose their marijuana use. Don't worry that your anesthesiologist is judging you. That's not our job! Our job is to understand your health and body in order to provide you with the safest and most pain-free procedure. This information is part of your confidential medical record, and accurate information is crucial to helping doctors provide good care.
Marijuana can affect the type and amount of anesthesia
The way(s) you use marijuana (smoking, edibles, etc.), how often you use, and how much all can affect how your body responds to anesthesia. Since marijuana and anesthesia both affect the central nervous system, people who use marijuana regularly may need different amounts of anesthesia medicines. In order to know which medicines and how much to use, your doctor needs to know ahead of time how much and how often you use marijuana.
Regular users of marijuana generally need larger doses of anesthesia medicines in order to achieve the same degree of sedation. If you don't tell your anesthesiologist how much marijuana you smoke, he or she may underestimate how much anesthesia will be needed for you to "go to sleep" and stay asleep during your procedure. For example, compared to nonusers, regular marijuana users (daily to weekly) need over three times as much more propofol to achieve adequate sedation for endoscopies. That is a huge increase in dose that your doctor would want to be prepared to administer.
The higher anesthesia dose required for regular marijuana users can lead to an increased risk of complications, such as decreased blood pressure and delayed awakening from anesthesia.
Marijuana use before surgery can increase the risk of complications
Other side effects of regular marijuana use can lead to serious complications of anesthesia. Inhaled marijuana can affect your lungs and increase phlegm, coughing, wheezing, and the risk of respiratory infections. These lung issues can lead to breathing problems during your anesthetic, such as increased airway sensitivity when the breathing tube is put into or taken out of the airway. This may feel like an asthma attack, with a sensation of difficulty breathing and decreased oxygen getting into the lungs. Regular users of marijuana can also have increased postoperative pain, which leads to higher opioid use during and after surgery. This puts regular marijuana users at risk for opioid use disorder after surgery.
Don't use marijuana the day of surgery — especially edibles
No matter how worried you are about your procedure, don't use marijuana to relax — you may end up with your surgery rescheduled or with serious complications. Regardless of how often you usually use marijuana, anesthesiologists agree that you should skip it completely on the day of surgery. You should not smoke or inhale marijuana the day of your surgery, and certainly you should avoid any edible marijuana the day of surgery, since the American Society of Anesthesiologists' guidelines for preoperative fasting do not allow any solid food for six to eight hours prior to anesthesia, in order to decrease the risk of food getting inhaled into your lungs. This can lead to aspiration pneumonia, a very serious complication that may cause death in some patients.
The physical effects of marijuana can increase the risk of complications, especially if consumed within an hour or two of anesthesia. Marijuana can raise your heart rate and lower your blood pressure. These changes are even more serious in patients with heart disease. In selected patient populations, this combination of decreased blood pressure and increased heart rate can cause ischemia (lack of blood supply) to the heart muscle, commonly known as a heart attack.
There are still many unknowns about marijuana
Your anesthesiologist needs accurate information about your marijuana use in order to plan safe anesthesia, and we know that no one should use marijuana on the day of surgery. Because of marijuana's classification as a drug of abuse, we cannot do medical research on marijuana without legislation to allow that research, and this includes research about how marijuana affects surgical procedures and aspects of anesthesia. The American Society of Anesthesiologists (ASA) has urged the federal government to allow medical studies and has endorsed bills to expand research in marijuana.
Your anesthesiologist just wants to keep you safe
The ASA has a list of eight things that you should tell your physician and anesthesiologist before surgery, and the use of marijuana is one of them. Please don't be afraid to disclose your use of marijuana to your physician, as it will not affect what we think of you. You will help us manage and adjust your anesthetic, prevent complications, and keep you as safe and healthy as possible.
Image: BraunS/Getty Images
About the Author
David Hepner, MD, MPH, Contributor
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