Episode #299 Cannabis And Anesthesia

“What I hope to see is more research and studies with the use of the high potency products, which are now being used, and perhaps a pause in states approving or further legalizing the product. Until we know more, we are seeing emergency visits, room visits, increasing. Patients are not expecting the adverse health events that are occurring.”

[Bechtel] Have you provided anesthesia care for a patient who uses cannabis? Are you asking patients about cannabis use during your preoperative evaluation? Here are some of the important physiological effects from cannabis use that anesthesia professionals need to be aware of:

• Altered drug metabolism
• Airway hyperreactivity
• Increased postoperative pain

Be on the look out for cardiovascular instability and unpredictable sedative requirements!

Stay tuned as we explore this topic further on the show today.

Hello and welcome back to the Anesthesia Patient Safety Podcast. I’m your host, Alli Bechtel, anaesthesiologist and podcaster.

Before we dive further into the episode today, we’d like to recognize Vertex, a major corporate supporter of APSF. Vertex has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Vertex – we wouldn’t be able to do all that we do without you!”

Our featured article is from the February 2026 APSF Newsletter. That’s right we are opening up the newest newsletter and there are some excellent articles to talk about. Our featured article is “Cannabis and Anesthesia: A 2025 Update on Perioperative Considerations” by Dylan Irving and colleagues. To follow along with us, head over to APSF.org and click on the Newsletter Heading. The first one down is the current newsletter. Then, you can scroll down until you get to our featured article and I will include a link in the show notes as well.

To help kick off the show today, we are going to be hearing from one of the authors. Here she is now.

[Meyer] “Hi, my name is Tricia Meyer. I’m a pharm d and an adjunct professor of anaesthesiology at the Texas a and m College of Medicine. I also serve as a co-chair for the Anesthesia Patient Safety Foundation, medication Safety Advisory Group. I am also an A-P-S-F member of the editorial board and the Committee on Education and Training.”

[Bechtel] I asked Tricia why she is so passionate about this topic. Let’s take a listen to what she had to say.

[Meyer] “This topic is very important for several reasons. With 40 states allowing medical marijuana and 24 states allowing recreational marijuana, the use of THC, which is the principle psychoactive cannabinoid has skyrocketed. 18 million Americans report daily or near daily use of the product. Additionally, the pot used from the 1960s, the 1970s, and up to the 1990s is nothing like the highly concentrated product we see in use today with potency, quadrupling, or even more Another important part of this problem is that much of the science and the literature on marijuana was done with the lower potency products.”

[Bechtel] Thank you so much to Tricia for helping to set the stage. Almost 4 years ago, we first talked about the perioperative considerations for cannabis use during anesthesia care. This was episodes #108 and #109. We are bringing you updated considerations today and this update is timely since adult cannabis use in the United States has increased considerably with the expansion of state legalization. By mid-2025, medical cannabis is authorized in 40 states, the District of Columbia, and several US territories, and recreational adult use is legal in 24 states and DC. Along with the increased use, there has also been an increase in research in this area to help guide anaesthetic management.

Let’s start the conversation with pharmacological considerations. We need a quick review and some definitions first. The phytocannabinoids  include THC, tetrahydrocannabinol, and CBD, cannabidiol, are the most commonly known botanical cannabinoids. THC is the main psychoactive compound in the cannabis sativa plant, which is the one of the most commonly occurring subspecies. CBD is an active cannabinoid, but not mind-altering.

So, how does this drug work? Cannabinoids bind to cannabinoid receptor type 1 and type 2 in the body. These receptors are part of the endocannabinoid system and located throughout the body and brain. The endocannabinoid system is responsible for regulating learning and memory, emotional processing, sleep, temperature control, pain control, inflammatory and immune response, and appetite. The CB1 receptor is involved in the nervous system, motor function, memory, analgesia, and others. The CB2 receptor is involved with anti-inflammatory and pro-inflammatory reactions. Endogenous endocannabinoid stimulation of the CB1 receptors does not cause the same level of euphoria that may be seen following THC or marijuana use. Endocannabinoids undergo rapid breakdown by enzymes. For all of our runners out there, some researchers have suggested that the runner’s high, the feelings of bliss and well-being during a run, may be due to the release of endocannabinoids rather than from endorphins.

Phytocannabinoids may act as partial agonists, full agonists, or antagonists at the cannabinoid receptors. Plus, down regulation of these receptors can occur with partial agonist effects from THC that can lead to tolerance and decreased effects. Therapeutic actions of THC and CBD include the following:

Analgesic

Anti-emetic

Anti-inflammatory

Antiseizure

Neuroprotection

The method of administration is important for drug effects and plasma levels. Inhaling or smoking cannabis has a rapid onset with THC detected in plasma within seconds. After 5-7 minutes of smoking with 10-15mg THC, the peak plasma levels will be 100mcg/L. Metabolites will appear in the urine and faeces as glucuronide conjugates with some of the urine metabolites lasting for up to 2 weeks.

Acute THC or THC/CBD intoxication may have the following signs and symptoms:

Increased disinhibition

Impaired memory

Impairments in learning, attention, attentional bias, and psychomotor function.

Adverse effects may be mild to severe and depend on the drug concentration, route of administration, and prior exposure. These include:

Euphoria

Anxiolysis

Tachycardia

Sensory amplification

Postural hypotension

Conjunctivitis

Hunger

Dry throat, mouth, and eyes

More serious side effects may include panic attacks, myoclonus, psychosis, hyperemesis, hypertension, tremors, seizures, inhalation burns, hallucinations, unconsciousness, acute respiratory distress syndrome, and bronchospasm.

There can also be ongoing and long-term effects that persist even after stopping use.

Drug-drug interactions may occur with THC with effects on absorption, metabolism, excretion, or pharmacodynamic effects. The action of THC may be intensified or dampened by some prescription drugs and the opposite may occur. The pharmacological action and side effects of prescription drugs may be affected by THC. The most common serious drug-drug interactions with cannabis and cannabinoids are warfarin, valproate, tacrolimus, and sirolimus with reported adverse events including bleeding, altered mental status, higher anaesthetic requirement, and gastrointestinal distress. There is a good resource for clinicians to determine possible drug-drug interactions between cannabinoids and common prescription medications. It is a free online tool, www.CANN-DIR.psu.edu. I will include the link in the show notes so that you can check it out.

The interactions between THC and CYP inhibitors and inducers are notable as well. CYP inhibitors may increase the bioavailability of THC and increase the desired or unwanted effects. CYP inducers may decrease the effects of THC. Check out Table 1 in the article for a list of common CYP inhibitors and inducers.

Next up, we are going to discuss the perioperative considerations. Table 2 is an excellent resource with all the considerations related to cannabis use for anesthesia professionals. This would be a good teaching resource for anesthesia trainees or a discussion at your next anaesthetic department meeting.

Let’s start with the preoperative period. It is important to obtain a history of cannabis use and document the type of products, route and frequency, dose, time of last use, and presence of withdrawal symptoms. You can also ask about use of cannabis with other products including alcohol, opioids, or sedatives and if any adverse reactions have occurred. This information can help identify cardiovascular and respiratory risks, possible withdrawal, delayed gastric emptying from THC, and anaesthetic challengers during intoxication. Cannabis use is associated with higher rates of perioperative complications of cardiorespiratory events and wound-related issues. There is evidence that cannabis use shortly before surgery may increase the risk for myocardial infarction especially in patients with coronary artery disease. Elective surgery may need to be delayed and for patients with symptoms or high-risk, further cardiac workup may be necessary. When patients present with acute intoxication with anxiety, paranoia, or psychosis, elective surgery should be delayed until patients are sober. For patients seen in a preop anesthesia clinic prior to surgery, advice should be given about temporary cessation of cannabis, document use in the medical record, and consider options for postoperative analgesic management. At this time, there are no strong, evidence based guidelines for how long to discontinue cannabis use prior to surgery.

Once you are in the operating room, be on the lookout for higher anaesthetic requirement. Regular cannabis use may increase propofol dose required for induction and procedural sedation. Patient may require higher doses of IV and volatile agents to achieve adequate anaesthetic depth. There is the potential for drug-drug interactions that may blunt or potentiate the effects of cannabis especially with sympathomimetics, vasoactive agents, and CYP inducers and inhibitors. It is important to monitor for cardiopulmonary complications and be prepared to treat. Patients who inhale cannabis are at risk for increased airway reactivity and bronchospasm. Patients with acute intoxication are at the highest risk for emergence agitation and hemodynamic instability. Research has been done in this area to help inform our anaesthetic management for cannabis users. There are 2 meta-analyses with 8 studies and over 2,000 patients and with 11 studies and over 4,000 patients that demonstrated increased requirements for IV anaesthetics, especially propofol for cannabis users undergoing general anesthesia and sedation. Two retrospective studies revealed increased requirements for inhalational anaesthetics as well. There is a recent prospective study that reported significantly higher doses of sedative agents including fentanyl, midazolam, and propofol for marijuana users. We are looking forward to more research in this area going forward to help guide formal clinical recommendations.

In the recovery room, there are additional considerations since patients may have higher postoperative pain scores and increased opioid consumption. Multimodal analgesia and non-opioid adjuncts are important for adequate pain control. Patients may develop symptoms of withdrawal from cannabis use which presents as irritability, nausea, anxiety, and sleep disturbance. Withdrawal may occur 1-2 days after the last use and symptoms can last for 1-2 weeks. There are reports of postoperative hypothermia and shivering among cannabis users and this may be due to type 1 receptor activity instead from withdrawal.

Let’s do a quick review of the perioperative considerations. Preop: Screen for cannabis use and assess cardiovascular, respiratory, and withdrawal risks. Intraop: Utilize individualized dosing, careful monitoring, and be prepared for hemodynamic or airway complications. Postop: anticipate increased analgesic requirements, plan for multi-modal analgesia, and monitor for withdrawal symptoms. There is a call to action for anesthesia professionals to stay informed of new data related to cannabis use to optimize perioperative safety and anesthesia care.

Before we wrap up for today, we are going to hear from Tricia again. I also asked her what she hopes to see going forward. Here is her response.

[Meyer] “What I hope to see is more research and studies with the use of the high potency products, which are now being used, and perhaps a pause in states approving or further legalizing the product. Until we know more, we are seeing emergency visits, room visits, increasing. Patients are not expecting the adverse health events that are occurring.”

If you have any questions or comments from today’s show, please email us at [email protected]. Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice. We hope that you will visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.

That’s it for today’s episode. If this conversation sparked a thought or gave you something to take back to your practice, make sure you’re subscribed so you don’t miss future episodes. You can listen wherever you get your podcasts, and sharing the show with a colleague really helps spread the word about improving patient safety in anesthesia. Thanks for listening.

Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

© 2026, The Anesthesia Patient Safety Foundation