All patients who undergo procedures that require regional or general anesthesia should be asked if, how often, and in what forms they use the drug, according to recommendations from the American Society of Regional Anesthesia and Pain Medicine.
One reason: Patients who regularly use cannabis may experience worse pain and nausea after surgery and may require more opioid analgesia, the group said.
The society’s recommendations – published in Regional Anesthesia and Pain Medicine – are the first guidelines in the United States to cover cannabis use as it relates to surgery, the group said.
Use of cannabis has increased in recent years, and researchers have been concerned that the drug may interact with anesthesia and complicate pain management. Few studies have evaluated interactions between cannabis and anesthetic agents, however, according to the authors of the new guidelines.
“With the rising prevalence of both medical and recreational cannabis use in the general population, anesthesiologists, surgeons, and perioperative physicians must have an understanding of the effects of cannabis on physiology in order to provide safe perioperative care,” the guideline said.
“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, PhD, ASRA president and senior author of the guidelines, said in a news release about the recommendations.
Although some patients may use cannabis to relieve pain, research shows that “regular users may have more pain and nausea after surgery, not less, and may need more medications, including opioids, to manage the discomfort,” said Dr. Narouze, chairman of the Center for Pain Medicine at Western Reserve Hospital in Cuyahoga Falls, Ohio.
Risks for vomiting, heart attack
The new recommendations were created by a committee of 13 experts, including anesthesiologists, chronic pain physicians, and a patient advocate. Shalini Shah, MD, vice chair of anesthesiology at the University of California, Irvine, was lead author of the document.
Four of 21 recommendations were classified as grade A, meaning that following them would be expected to provide substantial benefits. Those recommendations are to screen all patients before surgery; postpone elective surgery for patients who have altered mental status or impaired decision-making capacity at the time of surgery; counsel frequent, heavy users about the potential for cannabis use to impair postoperative pain control; and counsel pregnant patients about the risks of cannabis use to unborn children.
The authors cited studies to support their recommendations, including one showing that long-term cannabis use was associated with a 20% increase in the incidence of postoperative nausea and vomiting, a leading complaint of surgery patients. Other research has shown that cannabis use is linked to more pain and use of opioids after surgery.
Other recommendations include delaying elective surgery for at least 2 hours after a patient has smoked cannabis, owing to an increased risk for heart attack, and considering adjustment of ventilation settings during surgery for regular smokers of cannabis. Research has shown that smoking cannabis may be a rare trigger for myocardial infarction and is associated with airway inflammation and self-reported respiratory symptoms.
Nevertheless, doctors should not conduct universal toxicology screening, given a lack of evidence supporting this practice, the guideline stated.
The authors did not have enough information to make recommendations about reducing cannabis use before surgery or adjusting opioid prescriptions after surgery for patients who use cannabis, they said.
Kenneth Finn, MD, president of the American Board of Pain Medicine, welcomed the publication of the new guidelines. Dr. Finn, who practices at Springs Rehabilitation in Colorado Springs, has edited a textbook about cannabis in medicine and founded the International Academy on the Science and Impact of Cannabis.
“The vast majority of medical providers really have no idea about cannabis and what its impacts are on the human body,” Dr. Finn said.
For one, it can interact with numerous other drugs, including warfarin.
Guideline coauthor Eugene R. Viscusi, MD, professor of anesthesiology at the Sidney Kimmel Medical College, Philadelphia, emphasized that, while cannabis may be perceived as “natural,” it should not be considered differently from manufactured drugs.
Cannabis and cannabinoids represent “a class of very potent and pharmacologically active compounds,” Dr. Viscusi said in an interview. While researchers continue to assess possible medically beneficial effects of cannabis compounds, clinicians also need to be aware of the risks.
“The literature continues to emerge, and while we are always hopeful for good news, as physicians, we need to be very well versed on potential risks, especially in a high-risk situation like surgery,” he said.
Dr. Shah has consulted for companies that develop medical devices and drugs. Dr. Finn is the editor of the textbook, “Cannabis in Medicine: An Evidence-Based Approach” (Springer: New York, 2020), for which he receives royalties.
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