Cannabis and surgery: Be honest with your doctor – and anesthesiologist  

If there is one person you never want to lie to about substance use, it’s your doctor. That is especially important if the doctor is an anesthesiologist who will be taking care of you during a surgery.

Now that cannabis is legal in Massachusetts, more people than ever are using it and the population of users tends to skew older than you might suspect, according to anesthesiologist Eileen Micaroni, MD, at Cape Cod Anesthesia Associates in Hyannis.

Dr. Micaroni thinks that the reason some patients might not want to confess their use of marijuana is because even though it is legal, a lot of people still attach a stigma to it. She assures patients that she does not ever judge them. For her, the knowledge of substance use is purely about patient safety.

“I am literally there to get you safely through surgery,” she said. “I do not judge nor care about what anybody does in their personal life. I just want information so that I can make the best decisions to keep someone safe and comfortable.”

Higher Anesthetic Requirements

Marijuana causes many different problems for people during surgery. Since it works on the same receptors of the brain as alcohol and has cross tolerance with pain medications like fentanyl and morphine, a patient who regularly uses marijuana (or alcohol and opioids) is going to have higher anesthetic requirements, Dr. Micaroni said. They will also generally have more pain after the surgery.

“The other very significant thing we see with increased marijuana use with people who smoke it, we would obviously see the same complications we see from smoking tobacco,” she said. “They have increased airway irritation, and they are more at risk of respiratory complications after a procedure.”

Because marijuana slows digestion, another complication is that fasting overnight might not empty the contents of their stomach fully enough. That increases the risk of aspirating gastric content into their lungs.

Marijuana also slows down the metabolism of medications in a patient’s system, which can be dangerous if the patient is on a blood thinner like Warfarin or Eliquis. From an anesthesiologist’s standpoint, that would be important information to have if the planned surgery will be done with spinal anesthesia or an epidural anesthesia. Higher levels of blood thinner in their body puts them at risk of having a bleed in their back that could be potentially life threatening, she said.

“There is really strong data that says that people who use marijuana are at increased risk of cardiovascular complications after surgery, specifically a heart attack in the peri-operative period,” Dr. Micaroni said. “They say the risk is higher in the first couple of hours after you smoke it, but for people who use it chronically, there is strong data that they definitely have a higher risk of a heart attack after surgery. So, it is absolutely a good thing to know.”

Not Hiding Anything

The other reason to be honest about substance use is that your anesthesiologist is going to figure it out during surgery anyway.

In response to pain (even while under anesthesia), someone who regularly uses marijuana, either by smoking or ingestion (as well as those who regularly drink alcohol or use opioids), will have an increase in blood pressure and heart rate, and their breathing quickens in a similar manner to hyperventilating. Dr. Micaroni would then immediately suspect that the patient omitted relevant information about their alcohol and marijuana consumption. These patients will need more pain medication during surgery and afterwards, since they have basically altered their pain receptors in a way that they require more than someone who doesn’t take or use those substances on a regular basis, she said.

“Unfortunately, at that point, because they didn’t tell me this and I wasn’t anticipating it, I’m a little behind on their pain control,” she said. “Usually, I can try to catch up, but it’s nice to know ahead of time because they are at risk of the complications we talked about. Instead of having to figure it out as we go along, it’s just better when I can anticipate all of this and be prepared for it.”

Since the legalization of marijuana is so new, there aren’t good guidelines about how long before a planned surgery a patient should refrain from use, but Dr. Micaroni said the sooner the better. Twelve weeks abstinence is what is usually recommended for tobacco products, so it’s a safe guess that could apply to cannabis too.

“It’s hard for people who use marijuana for sleep and chronic pain,” she said. “It decreases their consumption of things like oxycodone and morphine, so in that way maybe it’s beneficial because they are getting less side effects from those drugs. But by the same token, they’re going to see more pain after surgery anyway so it’s a hard thing to navigate sometimes.”