ST. LOUIS — Expect to be asked more about cannabis use — what type, how much and how often — when preparing for an upcoming surgery as researchers learn more about complications associated with marijuana and anesthesia.
New U.S. guidelines released in January say all patients undergoing procedures that require going under should be asked details about their marijuana consumption.
That’s because regular users may require more anesthesia and experience worse pain and nausea after surgery, according to research gathered as part of developing the first-ever guidelines for anesthesiologists when it comes to patients’ cannabis use.
Not only are those who come to a surgery appointment high unable to properly consent to the procedure, the risk of having a heart attack increases within one to two hours of smoking weed, the guidelines warn.
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Dr. Samer Narouze, president of the American Society of Regional Anesthesia and Pain Medicine, the group that developed the guidelines, urged patients to be honest with their surgeons and anesthesiologists. Doctors may have to change the anesthesia plan or delay the procedure.
“We need to know if you are using and when and what you are using to plan for a safer and smoother anesthetic for patients … otherwise you will suffer,” Narouze said. “I mean who wants to suffer from pain after surgery, or who wants to have a heart attack?”
Two leading anesthesiologists with SSM Health said the guidelines are much-needed as they care for more patients experiencing the effects of using marijuana and expect to see more.
Missouri is among 21 states that have legalized recreational marijuana, with stores getting the green light to begin sales earlier this month.
Dr. Mick Kilkelly, chief of the adult anesthesiology division at SSM Health St. Louis University Hospital, said since he started practicing in the mid ’90s, the focus has gone from crack cocaine to opioids.
“We’ve been focused on these quote ‘harder drugs’ and not haven’t given really a lot of thought to what the implications of cannabis might be,” Kilkelly said.
‘They don’t know’
The guidelines were developed because along with the increasing use of cannabis, doctors are experiencing issues in the operating room, Narouze said. About 10% of Americans use cannabis monthly, and it is the most commonly used psychotropic drug after alcohol, according to the U.S. Substance Abuse and Mental Health Services Administration.
Dentists also report seeing more patients who have been affected. A recent survey conducted by the American Dental Association found that 56% of dentists reported having to limit treatment to patients who were high from cannabis or another drug, and 46% reported needing to increase anesthesia to treat patients because of their drug use.
Physicians lack formal education about cannabis in medical schools, Narouze said, so the guidelines include information about how cannabis compounds work with receptors in the body, and how the compounds can react with other drugs.
“Only recently, few medical schools are starting to add cannabinoid pharmacology into their medical school curriculum,” Narouze said. “So, they don’t know.”
Dr. Scott Harshman, director of outpatient anesthesiology procedures at St. Louis University Hospital, said he welcomed the guidelines, especially after moving to St. Louis from Nashville, Tenn., over a year ago.
“Having Illinois here just right across river,” where recreational marijuana was legalized three years ago, Harshman said, “that was one of first things I saw, that there was quite a bit more cannabis use than I was used to.”
Harshman said prior to recreational marijuana becoming available in Missouri, he had two patients in one day come to their surgery appointments high. They each had smoked a joint in their cars in the parking lot.
Both were sent home, he said, because they could not properly consent to the risks of surgery, and because the cannabis may have been laced with other unknown narcotics.
He has since learned from the new guidelines that patients also have a nearly a fivefold increased risk of heart attack within one to two hours of smoking marijuana, he said. (Smoking the plant causes THC levels in the blood to quickly peak, while ingesting it does not.)
“What this article highlighted was the cardiopulmonary concerns with acute intoxication,” Harshman said, “which were eye-opening.”
The paradoxical effect
Kilkelly said he thinks one of the guidelines’ most important lessons is how heavy cannabis use (at least 20 days a month) or high-potency variations of the drug with high levels of THC — the chemical that causes the high — does not mean one will experience more of its positive medicinal effects.
“There’s reasonable evidence now that is presented in this paper to suggest that people who are regular users of THC actually have more trouble with pain, and more trouble with nausea after anesthesia, which is a little counterintuitive based on what most of us think of medical marijuana is being used for,” Kilkelly said.
Narouze called this the paradoxical effect.
“A small concentration of THC, like what we see in the medicinal cannabis, it controls pain. But a high potency of THC, it causes the opposite. It makes the patient more sensitive to pain,” Narouze said.
Doctors also experience heavy cannabis users needing more anesthesia.
“In a nutshell, if they are tolerant to cannabis, they might be tolerant to other anesthetic medications,” Nazoue said. “We see this frequently. They require higher doses of propofol to fall asleep.”
After surgery in the recovery room, he said, heavy or high-potency cannabis users tend to have more pain, nausea and vomiting, low body temperature and shivering, and hypertension.
Harshman said anesthesiologists already take extra precautions to keep patients warm who are elderly and have heart conditions because shivering significantly increases the work of the heart, but now cannabis use will be on his radar as well.
“We are going to have to be even more vigilant because of the potential post-op complications that we could have from that, especially in the heavy user of marijuana,” he said.
Researchers are still trying to determine why the risk for complications, Narouze said. It may be because patients are experiencing withdrawal symptoms after abstaining from use prior to surgery.
Treatment of the post-operative pain can also be difficult, he said, because heavy users are not only more tolerant to cannabis, they are also likely to have “cross-tolerance” — they are also tolerant to opioid pain medications.
The guidelines recommends doctors try other pain medications and even nerve blocks or other numbing techniques to block the pain. In limited situations where pain can’t be controlled, patients can receive a form of THC called Dronabinol approved by the U.S. Food and Drug Administration for cancer patients to treat nausea and vomiting.
“It’s not FDA-approved for pain,” he said, “however, this is the only THC pharmaceutical, and we recommend to use it to treat withdrawal symptoms.”
Harshman said the opioid epidemic has already steered doctors towards finding other ways besides opioids to control pain, because uncontrolled pain can lead to chronic pain.
“This going to add to that thought process, because to be honest, I hadn’t previously considered marijuana as something that would greatly impact our post-operative course,” Harshman said. “Now that has certainly been brought to light that it does.”
Kilkelly said patients in trauma and emergency situations don’t always have the luxury of delaying surgery. That is where good communication with surgeons is key, where together they weigh a patient’s risk factors.
“The surgeon may say, ‘Oh, a fivefold increase in heart risk? Yeah, we can wait, it’s not that urgent,’” Kilkelly said. “Or sometimes the answer is, ‘Hey if we wait an hour, that might be the difference between this fellow losing his leg or not. So, thinking we need to do some extra monitoring, be hypervigilant and go.’”
A lot of questions remain, such as: If patients stop using cannabis before surgery to improve outcomes, will they get into that withdrawal window? Will that end up making outcomes worse? Which cannabis users require more anesthetic and how much? More rigorous research is needed, Narouze said.
In meantime, one thing is for sure, Kilkelly said. “Soliciting information is very reasonable and appropriate and we will dig down a little deeper than before … when someone says, ‘Yeah, I smoke pot.’”
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