Cannabis Use and Anesthesia: What Patients and Doctors Need to Know

As cannabis legalization becomes widespread throughout the country, so does the number of adults who choose to use cannabis for various medical or recreational purposes. Whether it be monthly, weekly, or daily use, cannabis consumption can have a profound impact on all other aspects of health. And that impact can vary widely from person to person, as different cannabinoids, dosages, and application methods can affect each person differently. Unfortunately, many cannabis consumers choose to keep their use to themselves and not disclose their consumption to their doctors, not realizing that they may be putting themselves in danger. This is especially true when it comes to patients undergoing certain medical procedures, such as surgery or other treatments that require anesthesia.

The Need for Sedation
Surgery is a major part of our American health care system. From mild, noninvasive surgeries for routine problems such as eye or dental issues to large, invasive surgeries that can take hours to complete, these events take place every day. The International Journal of Surgery estimates that more than 310 million major surgeries take place around the world each year, and this doesn’t even account for minor surgeries. Major surgeries are invasive, and patients have a long road to recovery. It’s estimated that 1% to 4% of those who undergo major surgery will die during or after the procedure, and up to 15% will experience significant postoperative morbidity.1

While not guaranteed, there are many lifestyle factors that can influence a patient's chance of survival and recovery success. That’s why many patients are screened for various health and lifestyle factors before a planned surgery. Whether the surgery is major or minor, routine or lifesaving, one goal remains—to keep the patient out of pain and as comfortable as possible. Thankfully, advances in medicine have made that happen thanks to anesthesia.

Anesthesia is the administration of a medication to reduce pain during a procedure. Depending on the type of anesthesia used, the patient may or may not be conscious during the operation. The administration of anesthesia is so important and delicate that anesthesiologists train for years to ensure they have the knowledge and experience to make such important, life-altering medical decisions with their patients. Their ultimate goal is to keep the patient as comfortable as possible while remaining as safe as possible. Too much anesthesia or not the right type can have debilitating, even deadly, consequences for patients.

There are four primary types of anesthesia: general, regional, local, and monitored anesthesia care.2 With general anesthesia, the patient is not conscious during the procedure. Regional anesthesia is meant to affect one specific area of the body; for example, an epidural can provide pain relief from the waist down. Local anesthesia is characterized by the use of medication to affect a specific area, for example, an injection in the gums to provide numbness or pain relief at the area of an infected tooth. Monitored anesthesia care means that the anesthesiologist is with the patient throughout a procedure and can adjust the type and dose of anesthesia as needed to provide the most comfort. During sedation, patients’ health status must be monitored, including their heart rate, blood pressure, breathing rate, and level of awareness. The type of anesthesia that’s provided to a patient will depend on a number of different factors including the type of surgery performed, length of time sedation is required, and the patient's baseline health status. Ultimately, the decision will be made by the patient, provider, and anesthesiologist.

In certain traumatic cases, there’s no time to evaluate the patients’ health status before the need to administer anesthesia. In these cases, the only goal is to keep patients as comfortable as possible while trying to save their lives. But in many other cases, surgeries are planned weeks, if not months, in advance, leaving the care team ample time to come up with an anesthesiology plan that’s tailored to the unique individual. In these cases, the patients’ baseline health is always examined to determine whether they’re healthy enough to make it through the procedure. Patient safety is always the priority. In some cases, if the patient is found to be too sick, the team will postpone the surgery until they are well again. What constitutes “too sick” will depend on the type of surgery that needs to be performed and the risk/benefit analysis. Factors that can determine the safety of a procedure include the patient's medical history, list of current conditions, potential allergies, and currently prescribed medications. Other lifestyle factors considered include body weight, activity level, level of alcohol consumption, smoking (whether cigarettes or cannabis), and drug use. In an ideal scenario, patients are honest and truthful with their providers about their health and lifestyle conditions. Unfortunately, in some cases, patients are not open and honest about their cannabis consumption, whether for legal or personal reasons. While the patient may think that they’re doing the right thing and keeping themselves safe from repercussions, many don’t realize that they’re putting their health and the success of surgery at risk.

Cannabis and Anesthesia Research
There’s been a fair amount of research done to suggests that cannabis consumers not only need more anesthesia during surgery to maintain pain control and sedation but also may have more pain during the recovery period. This is likely due to the metabolism of both THC, the active compound found in cannabis, and anesthesia medications being processed in the liver through the P450 pathway.4 This can lead to drug interactions that may or may not be beneficial to the patient. These drug interactions have the potential to become dangerous, causing cardiovascular and respiratory problems during anesthesia or surgery. Unfortunately, the variability of THC levels among plants, products, and application methods makes this potential for interaction difficult to study.

In 2020, the American Society for Anesthesiologists presented new and groundbreaking research suggesting that anesthesia affects cannabis consumers differently than it does nonconsumers.3 While there’s been research to suggest that cannabis consumers need more anesthesia, this study was the first of its kind to specifically research cannabis consumers vs noncannabis consumers and their needs for anesthesia during surgery. This study, while small, examined 118 patients in a Colorado hospital who needed surgery to repair a broken leg. Of these 118 individuals, 25% reported using cannabis prior to the surgery, although there was no indication of a time frame, dose, or application method for use. This group, compared with the individuals who did not report cannabis use, required more of the anesthetic medicine use during the surgery itself and higher pain scores during recovery. Most notably, they required 58% more opioid medication during their recovery day spent in the hospital.

In 2018, a study published in the American Association of Nurse Anesthesiology Journal compared cannabis consumers with nonconsumers who underwent a more minor surgery, an esophagogastroduodenoscopy, which is relatively noninvasive and short in duration. This retrospective study compared 23 self-reported cannabis consumers with 23 consumers who did not self-report cannabis use. In review, no statistically significant differences in the amount of medication used—including propofol, fentanyl, or ketamine—were found. In addition, after 30-days, no adverse cardiac or respiratory events were reported between either group.5 This research suggests there may be a difference in the needs of individuals, depending on whether or not they will undergo a major surgery, which may require more pain relief and anesthesia needs.

In contrast, a 2019 study in the Journal of the American Osteopathic Association found the opposite to be true. This larger study examined 250 individuals and found that the group that self-reported cannabis use needed a statistically significant higher amount of sedation to maintain comfort throughout their endoscopic procedures.6 Ultimately, more research is needed to draw any concrete data on the exact interaction between THC and anesthesia.

What Clinicians Need to Know
There are many moving pieces to the cannabis and anesthesia puzzle, and different considerations must be taken at different times.7 Whether you are the clinician performing the procedure or a general practitioner discussing with your patient an upcoming surgery, the most important thing you can do is emphasize the need for your patient to be open and honest about their consumption. Assure them that this is in their best interest and will ultimately help protect their safety and comfort before, during, and after the event. Reiterate that this information will only be used to guide safe care and will not be disclosed elsewhere, to legal authorities, or otherwise.

Before Anesthesia
This is the best time to learn about a patient's cannabis use. During this time, the clinician should obtain a thorough medical history and a thorough cannabis use history. Some providers may ask the patient to record their daily intake, estimated dose, and application method leading up to the procedure or ask them to record their symptoms with and without the use and to note what would happen if they ceased use. Others will simply want a record of the date and time of last consumption. In some cases, the surgeon or anesthesiologist will request to delay surgery until the patient has ceased cannabis use for a particular period of time. This is all up to the discretion of the providing team. If there is no period of time between cannabis use and the procedure, it’s important to note the mental state of the patients and ask them if they are experiencing higher-than-normal levels of anxiety or paranoia. In addition, these patients may present with tachycardia and hypertension. These factors will all need to be accounted for before proceeding with surgery.

During Anesthesia
Both animal and human studies suggest that medication needs may vary between cannabis users compared with noncannabis users.7 During surgery, the anesthesiologist and team will need to remain aware of how much medication they’re administering to the patient, watch for signs of distress and discomfort, and act accordingly. They may need to adjust the amount of medication used depending upon the unique circumstance. There’s no specific data or recommendations for medication use specific to cannabis users, so the determination will need to be made on a case-by-case basis.

Post Anesthesia
As with all patients, the team will need to watch for signs of discomfort, along with signs of cannabis withdrawal symptoms, such as agitation or paranoia after surgery. It is important to keep in mind that a patient may be likely to report a higher pain score and require more opioid medication for comfort postoperatively.

What Patients Need to Know
Providers need to make their patients understand that as hard as it may be, as shameful as it may seem, or as scared as they may feel about the law, in order to receive the best care possible, they must disclose their cannabis use to their doctors. As a health care provider, I recently needed to undergo a procedure that required anesthesia. The surgery was planned, so a nurse from the anesthesiologist’s office called me several days before my procedure to ask me a variety of questions about my medical history. I found myself not wanting to disclose my cannabis use due to social conditioning; but knowing what I know, I disclosed my consumption truthfully. The nurse on the phone simply asked me about my medical card, consumption method, and frequency of use. There was no judgment or shame, just a simple exchange of information. She then made the recommendation to abstain from cannabis for two hours before surgery. Remind your patients that they are not doing anything wrong by choosing to use cannabis, and doctors are not looking to get them in trouble; they simply want to give their patients the best care possible. If the anesthesiologists know patients’ cannabis use in advance, they can prepare and anticipate that the patient may have different needs. They can truly give patients the best care possible because they have all the information they need to know. For patients still feeling vulnerable, you can recommend that they consider getting a medical marijuana card. In many of the stricter states, these cards can provide an extra layer of legal protection and an added sense of security when disclosing this critical information.

— Emily Kyle, MS, RDN, CDN, CLT, HCP, is a certified holistic cannabis practitioner.

References