Cannabis Users May Need More Anesthesia and Face Higher Surgical Complication Risk
Surgical considerations of marijuana use in elective procedures
Bottom Line
Chronic cannabis use can alter anesthesia requirements, increase airway and cardiovascular complications during surgery, yet most users never disclose their use to surgical teams.
Why It Matters
Tens of millions of Americans use cannabis and millions undergo surgery annually. Most cannabis users do not disclose their use, leaving surgical teams unprepared for altered anesthesia needs, airway complications, and cardiovascular instability.
The Backstory
The anesthesiologist is puzzled. The patient — a healthy 32-year-old undergoing a routine colonoscopy — should be deeply sedated by now. The standard dose of propofol went in smoothly. But the patient is still moving. Still responding to stimuli. Still aware.
Another bolus. Then another. Then midazolam on top. The doses are climbing well past what the textbooks say this patient should need. The anesthesiologist pulls up the chart. Vital signs are stable. No unusual medical history. No prior anesthesia complications.
Then a colleague leans over and asks the question that should have been asked during the pre-operative assessment: "Does this patient use cannabis?"
This scenario — repeated thousands of times in operating rooms and endoscopy suites across the United States — is what prompted Henry Huson and colleagues to review everything known about marijuana use and surgical outcomes.
The Review
Huson, Granados, and Rasko — spanning surgery at LSU Health Sciences Center, family medicine at Brown University, and plastic surgery at the University of Maryland — published a comprehensive review in Heliyon examining the surgical implications of cannabis use across multiple organ systems.
The review addressed four clinical questions: How should marijuana use be screened pre-operatively? What surgical complications can cannabis cause? How should surgeons manage cannabis-using patients? And are marijuana's effects similar to or different from tobacco's?
What they found was a remarkably under-studied problem with potentially serious consequences.
The Anesthesia Problem
The most immediately concerning finding is that chronic cannabis users may need dramatically more sedation.
220%
more propofol needed by cannabis users during endoscopy compared to non-users, according to Twardowski et al. (2019) — the most widely cited figure in the cannabis-anesthesia literature. Cannabis users needed 44.81 mg of propofol versus 13.83 mg for non-users.
However, this finding is contested. A subsequent matched study found no significant difference in propofol requirements (both groups needed a median of 200 mg, p = 0.82). The truth likely depends on the patient, the frequency of use, and the type of procedure.
Twardowski et al. (2019), JAOA; Alexander et al. (2022), J Perianesth Nurs
The mechanism is pharmacologically plausible. THC and propofol both act on the central nervous system, and chronic CB1 receptor stimulation produces cross-tolerance with GABAergic sedatives. Regular cannabis users develop tolerance not just to THC but to a broader set of CNS depressants — the same phenomenon seen with chronic alcohol use. An anesthesiologist who does not know a patient uses cannabis may underdose sedation, potentially resulting in awareness during procedures.
Airway Complications
Cannabis smoke is an irritant, and chronic inhalation produces measurable changes in the airways.
The review recommended avoiding elective operations entirely if a patient has been recently exposed to cannabis smoke, and suggested dexamethasone (1 mg/kg every 6-12 hours) if signs of airway obstruction develop.
Cardiovascular Risks During Surgery
Cannabis adds cardiovascular stress on top of the physiological stress of surgery itself.
The Disclosure Problem
Perhaps the most practically important finding was not pharmacological but behavioral: most cannabis users do not disclose their use to their surgical team.
The reasons are predictable — legal concerns, stigma, the belief that cannabis is "natural" and therefore irrelevant to medical procedures, or simply not being asked. But the consequences of non-disclosure are concrete: underdosed anesthesia, unexpected airway complications, unexplained hemodynamic instability, and diagnostic confusion in the post-operative period.
Myth vs. Reality
Cannabis is natural and won't affect my surgery — I don't need to tell my doctor
Cannabis has measurable effects on anesthesia requirements, airway reactivity, cardiovascular stability, and potentially coagulation. Not disclosing cannabis use to your surgical team can lead to underdosed sedation (potentially causing awareness during surgery), unexpected airway emergencies, and post-operative complications. Your anesthesiologist needs this information to keep you safe.
The Evidence
Huson et al. (2018): 'Anesthesia should be avoided in any patient with cannabis use within the past 72 hours'
The Evidence Gap
The most striking conclusion of the review was how little rigorous evidence exists. Despite 40 years of research into cannabis physiology, the authors noted that "no investigation has taken place pertaining to patients' marijuana use and surgical considerations, such as effect on wound healing."
We know cannabis affects the cardiovascular system, the respiratory system, and the CNS. We know these effects are relevant to surgery. But we have almost no prospective surgical outcome data in cannabis users — no large studies tracking complication rates, no randomized trials of pre-operative cessation protocols, no validated screening tools designed for the surgical setting.
This is a remarkable blind spot given that tens of millions of Americans use cannabis and millions undergo surgery each year. The overlap between these populations is enormous and growing.
Pre-Operative Recommendations
Based on the available evidence, the review and related guidelines suggest:
Cite this study
Huson, Henry B; Granados, Tamara Marryshow; Rasko, Yvonne. (2018). Surgical considerations of marijuana use in elective procedures. Heliyon, 4(9), e00779. https://doi.org/10.1016/j.heliyon.2018.e00779