Cannabis Medicine Specialists Weigh In on Universal Screening Before Surgery

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With cannabis so readily available, it is no surprise the influential American Society of Regional Anesthesia (ASRA) and Pain Medicine finally decided to weigh in on the issue.

With cannabis so readily available, it is no surprise the influential American Society of Regional Anesthesia (ASRA) and Pain Medicine finally decided to weigh in on the issue.

Earlier this year, the organization—for the first time—issued guidelines that call for screening all patients for cannabis use before surgery.1 ASRA, with 5000 members in 66 countries, said in a January 3, 2023, announcement that it developed these recommendations amid concerns that cannabis might interact with anesthesia and lead to complications.2

“Before surgery, anesthesiologists should ask patients if they use cannabis—whether medicinally or recreationally—and be prepared to possibly change the anesthesia plan or delay the procedure in certain situations,” said Samer Narouze, MD, PhD, President of ASRA’s Pain Management Committee. “They also need to counsel patients about the possible risks and effects of cannabis. For example, even though some people use cannabis therapeutically to help relieve pain, studies have shown regular users may have more pain and nausea after surgery, not less, and may need more medications, including opioids, to manage the discomfort.”2

Dr. Narouze added: “We hope the guidelines will serve as a roadmap to help better care for patients who use cannabis and need surgery.”

Guideline Recommendations for the Perioperative Management of Cannabis

The guidelines were developed by ASRA’s 13-member panel of experts, which includes anesthesiologists, chronic pain physicians, and a patient advocate. Additionally, the guidelines were vetted by the American Society of Anesthesiologists. Of the 21 recommendations, 4 were categorized as Grade A, meaning they were backed by the highest level of evidence 1:

  • Screening all patients before surgery, including asking about the type of cannabis product used, how it was used (smoked or ingested), the amount used, how recently it was used, and frequency of use
  • Postponing elective surgery in patients who have altered mental status or impaired decision making at time of surgery
  • Counseling frequent, heavy users on the potentially negative effects of cannabis use on postoperative pain control
  • Counseling pregnant women on the risks of cannabis use to their unborn child

The remaining 17 recommendations have less support in the literature and are categorized as Grades B, C, D, or I (insufficient evidence). The ratings vary, depending on the strength of evidence and potential for benefit or harm, but several are categorized as I or insufficient evidence.1

Pain Researcher Weighs In

Screening patients for cannabis use before surgery is overall a good idea, said Kevin Boehnke, PhD, a Research Assistant Professor at the University of Michigan’s Chronic Pain and Fatigue Research Center in Ann Arbor.

“However, I believe this screening should be done verbally, with providers asking patients about whether they used cannabis or not. I would not endorse urine drug screens to test for cannabis in this context,” Dr. Boehnke said.

Notably, the guidelines also do not suggest universal toxicology screening for cannabinoids—giving it a Grade D, based on insufficient available evidence.1

 “Similarly, I would not endorse verbally screening patients if disclosing use would put patients at risk of legal backlash, inappropriate referral to addiction services, or losing access to medical care. For example, some clinics have policies where if a patient has a positive urine drug test for THC [delta-9-tetrahydrocannabinol], they may not fill certain other prescriptions. Such policies are punitive and should be stopped.”

Dr. Boehnke leads surveys and epidemiological studies to understand how people are currently using psychedelics and cannabis, as well as clinical trials to more directly investigate how these compounds influence pain. He pointed out that not all the ASRA recommendations are backed by sufficient evidence or are universally accepted. He called for more research to inform guidelines for other routes of administration besides smoking.

“We know, for example, that if you take CBD [cannabidiol] oil or drops, it’s going to last longer in your system than if you smoke a joint because it takes longer to be absorbed through the body,” said Dr. Boehnke. “While smoking, you have a quick spike of effect followed by a quick taper-off effect. I suspect they called out smoking because it’s known to be the most acutely hazardous form of cannabis ingestion.”

Other recommendations with a low level of evidence include the adjustment of ventilatory settings for patients with comorbid conditions and chronic cannabis consumption by inhalation (Grade C) and guidance for ventilation settings after acute inhaled cannabis use (Grade I, insufficient).1

Notably, ASRA does not suggest that patients abstain from cannabis for 1 week before major surgery nor does the society recommend routine perioperative tapering of cannabis use due to lack of published evidence. Although the ARSA guidelines are a start, the relationship between cannabis, anesthesia, and pain management needs further clarification.

Cannabis and Pain Management Relationship Is Poorly Understood

Patricia Frye, MD, board certified in pediatrics and trained in anesthesiology, cannabis science and medicine, said she is not surprised that the guidelines include considerations for adjusting ventilatory settings, noting that heavy use of vaped and smoked cannabis might cause pulmonary issues, such as bronchospasm as well as increased postoperative nausea and pain.

“Both modes of delivery damage cilia in the bronchial tree and contribute to increased sputum production,” she said. “Even though many cannabinoids are anti-inflammatory, THC does not appear to be as effective an anti-inflammatory as other phytocannabinoids such as CBD. And most heavy cannabis users are not using varieties that have significant amounts of CBD.”

Dr. Frye said it would be helpful to know if using cannabis in lower doses or other delivery methods, such as sublingual or edibles presents the same risks as smoked or vaped cannabis. The ARSA guidelines cite insufficient evidence (Grade I) for other routes of administration in addition to smoking.1

“My patient population does not fall into the demographics of those most likely to be heavy cannabis users or smokers, and have not reported to me any perioperative complications,” said Dr. Frye, Director of Takoma Park Integrative Care in Washington, DC. “On the contrary, most report a decreased need for opioid dosing when managing postoperative pain at home.”

“Smoking and dabbing highly concentrated THC products downregulates the endocannabinoid system, leaving fewer CB1 receptors to modulate pain signaling. This may explain why heavy users may experience suboptimal pain relief with typical analgesic dosing.” she explained.

Guidance Fails to Mention Emergency Surgery

Yvette Fouché-Weber, MD, is Director of the Trauma Anesthesiology Division at the R. Adams Cowley Shock Trauma Center in Baltimore, Maryland. Her emergency clinic receives numerous “poly-substance abusers” on cocaine, opioids, and other drugs that do interact with anesthesia.

But cannabis use before surgery has virtually “zero consequences,” she said.

“Our patients get into accidents and come to us with whatever they’ve been using. We don’t have the option of saying, ‘We can’t provide anesthesia for you.’ We also follow up on our patients’ post-op and there are no effects, whether it was emergency or elective surgery,” said Dr. Fouché-Weber, is also an Associate Professor of Anesthesiology at the University of Maryland School of Medicine. Notably, the guidelines only stipulate postponing elective surgery if the patient is mentally impaired (Grade A).1

She added that some of her patients are opioid-dependent and are on opioid-blocking agents. For these individuals, Dr. Fouché-Weber has used Marinol [dronabinol] as an analgesic because their opioid receptors are blocked.

“Some people have a preconceived notion about cannabis. … It makes no difference in a regional anesthesia whether they’ve used cannabis. We put patients to sleep here every day, all day long.”

Guidelines Need More Clarification

Mark Matsunaga, MD, does not seem convinced the new guidelines are absolutely necessary—nor that they are a bad idea.

An anesthesiologist with the Comprehensive Pain Center in Columbia, Maryland, he says it is difficult to get data because of the scarcity of controlled studies on cannabis. Given that only 4 of ARSA’s 21 guidelines have strong evidence (Grade A), there seems to be a consensus that more research is needed.

“In general, we have not found anything with the use of marijuana that contradicts any anesthetic,” he said. “There are lots of different ways we provide anesthesia for a patient. But the good thing about anesthesia these days is that with technology, we have the ability to adjust the dosage if they require more medicine to keep them asleep, so they don’t wake up too soon.”

Dr. Matsunaga agreed that anesthesiologists should know the cardiovascular and pulmonary implications of cannabis consumption for surgery—but that with all proper monitoring, it is not an issue.

“The consensus is that we know cannabinoids can have an impact on the amount of pain medicine required, or the amount of time required to wake up. These are all things we can adjust to,” he said. “But I’ve never heard of anyone saying that because you use marijuana, we can’t give you any anesthetic. Just having a history of using it should not cancel a procedure.”

For more on the cannabinoid screening guidelines put forth by the American Society of Regional Anesthesia (ASRA) and Pain Medicine, listen to AJEM’s Founding Editor in Chief, Jahan Marcu, PhD, discuss with public health expert Teresa Simon, MPH, on AJEM Live.


  1. Shah S, Schwenk ES, Sondekoppam RV, et al. ASRA pain Medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids. Reg Anesth Pain Med. 2023;48(3):97-117. doi:10.1136/rapm-2022-104013
  2. All patients should be screened for cannabis use before surgery, first U.S. guidelines recommend. News release. ASRA Pain Medicine Update. January 3, 2023. Accessed May 8, 2023.