To find out, Leafly reached out to Dr. David Bearman, a leader in cannabinoid medicine with a long career in drug abuse treatment and prevention, as well as author of the book Drugs Are Not The Devil’s Tools. Dr. Bearman’s credentials are extensive, ranging from his time serving the U.S. Public Health Service, to co-founding the American Academy of Cannabinoid Medicine, and much more.
The top question on the list: Is it safe to consume cannabis before a surgery? The answer, as one may expect, is not a simple yes or no, but instead relies on a few variables.
Note: Although Dr. Bearman is providing his expert opinion, as with all medical concerns, please consult with your doctor or surgeon about consuming cannabis before or after a surgical procedure. For more information, please refer to Leafly’s Terms of Service.
How long before surgery should one stop smoking cannabis, if necessary?
Bearman: The therapeutic and recreational effects of smoking cannabis usually last from 1.5 to 2.5 hours. For most surgeries, patients arrive at the hospital more than three hours prior to the surgery.
However, smoking can cause increased sputum production; for that reason, I would recommend not smoking cannabis for several hours prior to the surgery.
In terms of people who are using oral administration, the effects are going to last 3-6 hours. The night before surgery you are instructed not to eat anything after 10:00 p.m., so if you follow pre-op instructions, any effect from oral use would be gone well before the surgery.
There is some speculation that cannabis may affect the heart adversely. Are there any contraindications that heart patients should be aware of?
Bearman: I don’t want to glorify it by calling it a study, but a “study” was done on the East Coast a few years ago suggesting that people who smoke cannabis have an increased chance of having a heart attack. This was a retrospective study, never reproduced, and highly criticized, so I don’t think that I have seen any strong evidence that would suggest that cannabis has adverse cardiac effects.
The effects of cannabis on the heart are, how can I say, not very large and are variable. According to the 1999 Institute of Medicine report, the effects on blood pressure is that it may make it go up or down by five milligrams. That’s not an enormous amount; it’s basically the same as saying it doesn’t have much effect.
Now what I’ve noticed in a very small number of patients who have severe hypertension, is that cannabis can be amazingly successful in lowering their blood pressure to the normal range. I think that for people who have severe hypertension, I would suggest avoiding cannabis use before surgery, just because we don’t know what the effects of it are going to be. It’s possible that they might actually end up with hypotension—the combination of the cannabis and the anti-hypertension medication might be confusing to the anesthesiologist, who needs to know all the medications they’re on.
It’s very important that if a person is regularly using cannabis that they make sure they let the anesthesiologist know, so the anesthesiologist is aware of all of the medications they’re taking, including cannabis.
Now, in addition, there is supposed to be a fleeting effect [by cannabis] on pulse; it may cause it to increase. Frankly, I don’t know how fleeting it is, but I’ve seen thousands of patients and I don’t think the pulse rate of my patients is any more abnormal or higher than the average patient. So, I don’t think it’s a big deal, because it’s unlikely [your doctors] are going to let you smoke marijuana a half hour before your surgery.
What’s the best method of consumption before surgery?
Bearman: As mentioned, when cannabis is smoked it does cause an increase in cough and an increase in sputum production, so it’s probably not a great idea to smoke it prior to a surgery. If a patient is going to use it before surgery they’re going to want to choose a method other than smoking. Since vaporizing has 70% [fewer] irritants than smoking, if a patient wants to use the respiratory method, they should vaporize.
Is cannabis a beneficial choice as a post-op medicine?
Bearman: Yes, I think using it post-op is fine. Again, I wouldn’t smoke it. Particularly after abdominal surgery—that would be a contraindication. With abdominal surgery, doctors don’t want to see you coughing or vomiting. When a surgeon cuts into a person’s abdominal, sutures everything up, and then they start coughing or they start vomiting, the sutures start to come undone because of an increase in the inner abdominal pressure.
So, I would certainly think that cannabis is very useful for treating pain post-operatively, but in particular with abdominal surgery I wouldn’t smoke because of the possibility of coughing. If a patient wants to use the respiratory route they may want to try vaporizing, or it may be more prudent to use an under-the-tongue spray or other routes of oral administration.
Interestingly enough, historically if you go back to the 19th century, and certainly before that, cannabis was used as a childbirth anesthetic. One of the things we know about the cannabinoids is that many of them have analgesic properties, and THC has the most. It may decrease the dosage of pain medication that the person requires post-operatively.