Chronic cannabis use can alter anesthesia requirements, increase airway and cardiovascular complications during surgery, yet most users never disclose their use to surgical teams.
Anyone who uses cannabis and is planning surgery or a medical procedure.
220% more propofol needed (one study) — disclose cannabis use before any procedure
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.
Study Design
Surgical Considerations of Marijuana in Elective Procedures
9.5%+
US adults use marijuana
yet few trials examine surgical implications
4 questions
Structured review
screening, complications, management, tobacco comparison
40 years
Of physiological research
with almost no surgical outcome studies
72 hours
Recommended abstinence
before elective anesthesia per reviewed guidelines
Huson, Granados & Rasko (2018), Heliyon 4(9):e00779
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.
Anesthesia Risks
What Cannabis Use Means for Surgical Sedation
Increased propofol needs
Some studies show dramatic increases (220%+), others show no significant difference — likely depends on frequency and recency of use
Fentanyl requirements
14% more fentanyl needed in cannabis users during endoscopy
Midazolam requirements
19.6% more midazolam needed in cannabis users
Failed sedation
Case reports of patients requiring multiple boluses and additional agents to achieve adequate sedation
Awareness during surgery
If cannabis use is undisclosed, underdosing may lead to intraoperative awareness — one of the most distressing surgical complications
Huson et al. (2018); Twardowski et al. (2019)
Airway Complications
Cannabis smoke is an irritant, and chronic inhalation produces measurable changes in the airways.
Biological Mechanism
How Cannabis Smoke Affects the Airway
Proposed mechanism
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.
Cardiovascular Concerns
Cannabis and Surgical Cardiovascular Risk
Tachycardia
Heart rate increases within minutes of inhalation, peaks at ~30 minutes. One study found peak heart rate increased 24.1% in surgical patients vs. non-surgical — synergistic with surgical stress.
MI risk
4.8× increased risk of heart attack in the first hour after cannabis use (from the Mittleman data) — additional risk when combined with the hemodynamic stress of surgery
Arrhythmia risk
Elevated risk of atrial fibrillation and premature ventricular contractions, particularly concerning under anesthesia
Blood pressure instability
Initial hypertension followed by orthostatic hypotension — creates hemodynamic instability that complicates anesthetic management
Huson et al. (2018), Heliyon
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:
Cannabis and Surgery: What You Should Know
Disclose everything
Stop at least 72 hours before
Consider your method
Expect adjusted dosing
Peer-reviewed research
Do I need to tell my anesthesiologist I use cannabis?
Yes. Cannabis affects how much sedation you need, how your airway responds to intubation, and how your heart handles the stress of surgery. Not disclosing this information puts you at risk for inadequate anesthesia, airway emergencies, and post-operative complications. Your medical team cannot help you if they do not know what you are using.
How long before surgery should I stop using cannabis?
At minimum 72 hours, based on guidelines reviewed in this study. Heavy daily users may benefit from stopping 1-2 weeks before surgery to allow airway inflammation to resolve and tolerance to partially reset. Our guide to quitting before surgery covers the optimal timeline.
Will I need more anesthesia if I use cannabis?
Possibly. The evidence is mixed — some studies show dramatically increased requirements (220% more propofol), while others show no significant difference. The safest approach is to disclose your use so your anesthesiologist can plan accordingly and titrate to your individual response.
Is this only a concern with smoked cannabis?
Smoked cannabis carries the highest airway risk due to bronchial inflammation. But the sedation and cardiovascular effects come from THC itself, regardless of delivery method. Edible and vape users should also disclose their use before surgery.
Surgical considerations of marijuana use in elective procedures
Huson HB, Granados TM, Rasko Y (2018) · Heliyon
Related Research
Key studies in this area
Triggering Myocardial Infarction by Marijuana
Mittleman et al. (2001)
What the researchers found
Chronic cannabis users may require substantially more sedation for procedures (up to 220% more propofol in one study). Cannabis smoke produces airway hyperreactivity increasing intubation risks. Cardiovascular effects (tachycardia, blood pressure instability) compound surgical stress. Despite 40 years of physiological research, almost no prospective surgical outcome studies exist in cannabis users.
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 numbers in context
Propofol increase: 220% in one study (44.81 mg vs 13.83 mg), not confirmed in subsequent studies. 72 hours minimum abstinence recommended. 24.1% peak heart rate increase in surgical patients. Nearly half of heavy smokers (>100g/month) had recurrent rhinopharyngitis.
How the study worked
Narrative literature review addressing four clinical questions about marijuana use and surgical considerations.
What this study cannot tell us
Narrative review, not systematic. Based primarily on case reports, small studies, and physiological research rather than large prospective surgical outcome trials. The 220% propofol figure from Twardowski has been contested by subsequent studies.
How to read the evidence
Narrative review based on heterogeneous evidence — case reports, small studies, physiological research. No large prospective trials exist.
When this study was published
Published 2018. The evidence base has grown since but remains limited. Key propofol findings have been both supported and contradicted by subsequent research.
The bigger picture
Despite cannabis being used by nearly 10% of US adults, there is almost no prospective evidence on surgical outcomes. This represents one of the largest blind spots in perioperative medicine.
Questions still open
- Does cannabis affect wound healing? What is the optimal pre-operative cessation period? Do edible-only users face the same risks as smokers? Can validated screening tools improve surgical safety for cannabis users?
Common questions
Do I need to tell my doctor I use cannabis before surgery?
How long before surgery should I stop?
Read the original research
Surgical considerations of marijuana use in elective procedures
Heliyon, 4(9), e00779
Citation
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