The increasing normalization of cannabis use means a growing number of people regularly consume it for medical or recreational reasons. While cannabis is often viewed as relatively harmless, its active compounds introduce complex variables when combined with surgical procedures. The presence of cannabinoids can significantly alter the body’s response to both anesthesia and post-operative medications. For patient safety, anyone scheduled for surgery must have a frank discussion with their surgical and anesthesia teams about their consumption history.
How Cannabis Affects Anesthesia
Regular cannabis consumption profoundly changes how the body responds to anesthetic agents. Patients who use cannabis frequently often require substantially higher doses of sedation and pain medications to achieve and maintain unconsciousness. Studies show that chronic users may need 15% to 50% more of the intravenous sedative propofol to be properly sedated.
This increased requirement is partly due to the interaction between cannabinoids, such as tetrahydrocannabinol (THC), and the central nervous system. Chronic exposure can lead to pharmacological resistance, meaning standard doses of anesthetics are insufficient to suppress consciousness and reflexes. The metabolism of certain anesthetic drugs is also affected, as THC is processed by the liver’s cytochrome P450 enzyme system, the same pathway used by many anesthetic agents.
The cardiovascular system is also impacted, posing a threat during the operation. Cannabis use causes changes in heart rate and blood pressure, making the patient more susceptible to cardiovascular instability under general anesthesia. Acute use can lead to tachycardia, or an increased heart rate, which makes it harder for the anesthesiologist to maintain stable vital signs. Fluctuations in blood pressure or heart rhythm increase the risk of complications like a heart attack during surgery.
Airway Risks from Smoking
Smoking cannabis introduces mechanical and inflammatory risks to the respiratory system that are concerning before surgery. Inhaling smoke from burnt plant material causes inflammation and irritation in the airways, similar to the effects seen in tobacco smokers. This irritation leads to increased sputum production and can cause chronic symptoms like wheezing and coughing.
These pulmonary conditions make administering general anesthesia more challenging. The inflammation can cause the airways to be reactive, increasing the risk of laryngospasm or bronchospasm—sudden contractions of the breathing muscles. A reactive airway is more difficult to manage with a breathing tube, potentially leading to complications during intubation and ventilation.
Smoking cannabis can also cause swelling of the upper airway structures, such as the uvula. Swelling in this area can persist for up to 24 hours after use and may obstruct the airway, making breathing tube placement difficult. Furthermore, a compromised respiratory system increases the likelihood of post-operative lung complications, including pneumonia, which can lengthen recovery time.
Post-Operative Pain and Tolerance Changes
Regular cannabis consumption can significantly alter a patient’s baseline pain threshold, leading to a challenging recovery period. Paradoxically, despite cannabis being used for pain relief, users often report experiencing higher levels of pain after surgery compared to non-users. This heightened pain response means patients frequently require greater amounts of analgesic medication in the recovery unit.
This phenomenon is explained by a cross-tolerance that develops between cannabinoids and opioid medications. The pain-regulating receptors in the brain and spinal cord, including cannabinoid receptors, overlap with opioid receptors. Chronic stimulation of the cannabinoid system makes the body less responsive to traditional opioid pain relievers, necessitating a higher dose for effective pain control.
The need for increased doses of post-operative pain medication is concerning because it elevates the risk of side effects, such as respiratory depression and excessive sedation. Regular cannabis users also face a heightened risk of experiencing post-operative nausea and vomiting (PONV). This complication can be uncomfortable and place strain on surgical sites due to retching.
Recommended Time to Stop Use
The safest course of action is to stop using cannabis products well in advance of any scheduled operation to mitigate risks to anesthesia management and recovery. The medical consensus advises stopping all cannabis use at least 72 hours before a procedure to reduce the immediate risks of airway reactivity and cardiovascular instability.
For chronic, heavy users, a longer period of abstinence is recommended, ideally for several weeks. This extended break allows liver enzymes to return to a normal metabolic state and helps reduce the body’s tolerance to pain medications. Some experts suggest stopping all inhaled cannabis products, including smoking and vaping, for four to six weeks before surgery to minimize pulmonary complications.
It is necessary to be honest with the surgical team about the frequency, amount, and method of cannabis use. This information is used solely to create a personalized, safe anesthesia plan and an effective post-operative pain management strategy. Providing accurate details ensures the medical team can prepare for potential complications and adjust medication dosages appropriately for a smooth procedure and recovery.