If You Use Cannabis for Chronic Pain, Here's What Your Surgical Team Needs to Know

For the millions of people who use cannabis — whether prescribed for chronic pain, inflammation, or anxiety, or used recreationally — surgery can introduce an unexpected variable: the medications your anesthesiologist uses to keep you unconscious and comfortable may not behave predictably. A newly published clinical review on anesthesia and cannabis lays out why this matters, what the evidence says, and what both surgical teams and patients need to do before the operating table.

Why Cannabis Isn't Just Another Herb to Mention at Intake

Patients are routinely asked to list their supplements and medications before surgery — and cannabis often gets treated as a footnote. But the clinical reality is more complex. Cannabis contains two primary active compounds, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), both of which bind to receptors in the body known as CB1 and CB2. These receptors are found not just in the brain but also in the heart, lungs, and immune system, meaning cannabis can alter function across multiple organ systems simultaneously.

Beyond receptor effects, both THC and CBD affect the way the liver processes certain drugs — including several anesthetic agents. This is not a trivial interaction. A drug that is metabolized too quickly may wear off before the surgical team expects it to. One that lingers longer than intended can extend recovery time or amplify side effects. For anesthesiologists already calibrating complex drug combinations in real time, cannabis adds a layer of pharmacological unpredictability that cannot simply be ignored.

The Misconception That Medical Cannabis Is Risk-Free in the Operating Room

A persistent assumption among patients — and even some clinicians — is that medically prescribed cannabis is safe in all contexts simply because it is physician-supervised. The review challenges this view directly. While medical cannabis does carry a more favorable safety profile than recreational use, it is not without perioperative risk.

The key distinction is one of predictability. Medical cannabis typically involves standardized formulations and titrated dosing — meaning a patient's daily intake is relatively consistent and known. Recreational cannabis, by contrast, varies enormously in THC concentration, delivery method, and frequency of use, and is also more frequently combined with alcohol or other substances. Both groups require pre-surgical assessment, but recreational users carry a higher burden of unknown variables.

Three Body Systems That Cannabis Affects During Surgery

The review identifies cardiovascular, respiratory, and neurological effects as the three areas most relevant to perioperative risk — each with distinct implications for how a surgical team monitors and responds during a procedure.

The cardiovascular effects are particularly relevant for patients who already have underlying heart conditions. Tachycardia — a faster-than-normal heart rate — is a known acute effect of THC and can interact poorly with the hemodynamic changes that naturally occur during anesthesia. Hypotension during surgery can compromise blood flow to vital organs, and arrhythmias add unpredictability to cardiac monitoring.

For the respiratory system, regular inhaled cannabis causes similar airway irritation to tobacco, including chronic bronchitis and increased bronchial sensitivity. This becomes relevant when an anesthesiologist places a breathing tube or manages ventilation. An already-reactive airway may spasm in response to these procedures — a complication known as laryngospasm or bronchospasm that anesthesia teams train to manage but would rather prevent.

The Pain Paradox: More Cannabis Use, More Opioids After Surgery

One of the review's most clinically significant findings involves what happens to pain management after surgery. Patients who are chronic or high-dose cannabis users often require more opioid pain relievers in the postoperative period than non-users. This appears to be related to changes in how the brain's pain-signaling systems respond over time — a phenomenon tied to cannabis tolerance and cross-tolerance with opioid receptors.

For patients using cannabis specifically to manage chronic pain conditions, this creates a troubling surgical paradox: the very substance being used to reduce reliance on opioids may, after surgery, increase the need for them. The review recommends multimodal analgesic strategies — using several different types of pain relief together rather than relying primarily on opioids — as the preferred approach for cannabis users recovering from procedures. Postoperative nausea and vomiting prevention is also flagged as a priority, given cannabis users' complex relationship with nausea signaling.

What the Guidelines Say — and What You Should Do Before Any Planned Surgery

The American Society of Regional Anesthesia (ASRA) and PAIN guidelines, referenced in the review, now recommend that all surgical patients be screened for cannabis use as a standard part of preoperative assessment. This is not about judgment — it is about safety. The guidelines also recommend evaluating patients for cannabis use disorder, which affects how the body responds to both the drug and its absence.

In high-use patients, tapering or temporarily stopping cannabis before elective surgery is advised. Abrupt discontinuation, however, carries its own risks: withdrawal symptoms including anxiety, insomnia, nausea, and irritability can complicate recovery. The review specifically highlights the role of pain specialists in managing patients on long-term cannabis therapy, noting that oral cannabinoid substitution — switching from inhaled to a precisely dosed oral form — may be a safer bridge strategy than stopping entirely.

Elective surgery should be postponed entirely if a patient is acutely intoxicated. Acute intoxication amplifies cardiovascular instability, impairs airway reflexes, and interferes with the accurate dosing calculations anesthesiologists rely on.