By Pat Anson, PNN Editor

New medical guidelines recommend that all patients undergoing anesthesia should be screened for cannabis use before surgery, and that procedures should be delayed if patients are thought to be under the influence or impaired.

The guideline by the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine) is intended for anesthesiologists. It was developed by a panel of experts that included anesthesiologists, pain specialists and a patient advocate to deal with the growing number of people using either recreational or medical marijuana. An estimated 10% of Americans use cannabis monthly.

“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,” Samer Narouze, MD, ASRA Pain Medicine president, said in a statement.

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

The guideline recommends that patients be asked about their cannabis use before surgery, including whether it was smoked or ingested, the amount used, how recently it was used, and the frequency of use. It does not endorse drug testing of patients, meaning patients would have to be taken at their word.

If a patient admits recently smoking cannabis, the guideline recommends that non-emergency, elective procedures be postponed for a minimum of two hours because of the increased risk of a heart attack before, during and after surgery.

“In my opinion, these guidelines appear to be overly cautious at best and discriminatory at worst,” said Paul Armentano, Deputy Director of NORML, a marijuana advocacy group. “The relationship between cannabis and opioids is well-established, with nearly 100 papers in the literature showing that pain patients typically reduce or eliminate their intake of opioids over time following cannabis use.” 

Armentano cited a recent pilot study that found people who use cannabis respond no differently to local anesthesia than those who do not. Local anesthesia is different from general anesthesia because patients remain conscious during a procedure such as dental work. 

The evidence on cannabis and general anesthesia is rather thin, and because of that the ASRA guideline gives low grades to several of its recommendations, including the one about delaying surgery.  No recommendations are made about tapering cannabis use before or after surgery, or whether to prescribe opioids to patients who use cannabinoids due to “current lack of evidence.” Anesthesiologists are instead urged to use their own clinical judgement.   

In 2020, the Perioperative Pain and Addiction Interdisciplinary Network (PAIN) released more restrictive guidelines about cannabis use, recommending that heavy cannabis use be tapered or stopped before surgery.