Anesthesia Alert: New Cannabis Guideline Recommendations

Patients who use marijuana are at increased risk for negative outcomes.

The American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine) recently released the first U.S. guidelines on cannabis use in relation to surgery.

The move was spurred by increased use of marijuana throughout the past 20 years and subsequent concerns that THC can interact with anesthesia and lead to surgical complications.

The guidelines, which are based on an extensive literature review from ASRA Pain Medicine’s Perioperative Use of Cannabis and Cannabinoids Guidelines Committee, recommend that anesthesia providers screen all patients for marijuana usage — including the type of cannabis product used.

In all, the committee tackled nine questions and made a total of 21 recommendations using a modified Delphi consensus method with ­>75% agreement required for recommendation.­ Recommendation grades were based on the United States Preventive Services Task Force (USPSTF) process that assigns a letter (an A, B, C or D grade, or an I for insufficient) based on the depth of the evidence as well as the balance of benefits and harms. The most-pressing recommendations that received an A grade (the highest level of evidence) include:

• screening all patients before surgery,
• postponing elective surgery in patients who have altered mental status or impaired decision-making capacity at the time of surgery,
• counseling frequent, heavy users on the potentially negative effects of cannabis use on postoperative pain control, and
• counseling pregnant patients on the risks of cannabis use to the unborn child.

You can review the 21 recommendations in detail at osmag.net/cannabis. Samer Narouze, MD, PhD, senior author and ASRA Pain Medicine president, highlights the major takeaways from the guidelines and offers practical tips facility leaders can use to implement them.

Heavy users at risk

While many cannabis users will have uneventful surgeries and recoveries, some may encounter problems intra- or postoperatively. “Heavy frequent cannabis users may have more pain after surgery, while recent cannabis smoking before surgery may lead to cardiac problems — increased heart rate, irregular heart rate, even myocardial infarction (MI) — mainly in the first two hours after smoking cannabis,” says Dr. Narouze.

There’s a difference between medical cannabis and recreational cannabis. “Medical cannabis usually has low potency THC and is used under supervision by the clinicians,” says Dr. Narouze. “On the other hand, recreational cannabis may have very high THC concentrations, which can lead to significant problems with surgery.”

Medical cannabis usually has low potency THC and is being used under supervision by the clinicians. On the other hand, recreational cannabis may have very high THC concentrations, which may lead to significant problems with surgery.
Samer Narouze, MD, PhD

Cannabis or THC has a paradoxical effect, adds Dr. Narouze, which means in small doses it helps with pain and nausea, while high doses will lead to the opposite effect — increased pain and nausea/vomiting. Providers should also be aware of the major difference between smoking marijuana and consuming edibles. “Smoking cannabis leads to high concentration of THC in the blood very quickly (within a few minutes) and may lead to cardiac issues. Smoking over time will lead to lung problems as well,” says Dr. Narouze. “Oral cannabis [in edible form] has a much slower effect — over a few hours.”

Simple screening

If facility leaders are looking to implement ASRA Pain Medicine’s guidelines, Dr. Narouze suggests universally screening all patients for cannabis use. “The best way to implement this tool is by adding to the pre-anesthesia/pre-surgery questionnaire direct questions about using cannabis, not just Yes or No,” he says. Specifically, Dr. Narouze suggests adding the following questions to your facility’s pre-surgery questionnaire:

• How frequently do you use cannabis?
• When was it last used?
• How is it used (smoking or oral/edible form)?
• Why is it being used (medical or recreational)?

Patients may not understand why they need to be screened for their THC use, so it’s up to providers to explain the risks to their surgical outcomes if this information isn’t disclosed. “Recent cannabis use before surgery may be associated with an increased risk for cardiovascular problems — like increased heart rate or MI — during and after surgery,” says Dr. Narouze, adding that it’s important to alert patients that heavy cannabis use has also been linked to increased pain after surgery, and difficulty controlling immediate pain after procedures.

Heavy cannabis users may also respond differently to certain anesthetics. For example, regular marijuana users may require higher doses of propofol to fall asleep and/or suffer with cannabis withdrawal symptoms after surgery. These symptoms include restlessness, irritability, tremors, insomnia, nausea and vomiting.

As medical and recreational cannabis use among the general population continues to rise steadily, it’s critical for anesthesia providers and surgeons to understand the effects of cannabis on a patient to provide safe perioperative care and a satisfactory surgical experience. OSM