Regular users of cannabis may have more pain and nausea after surgery. What anesthesiologists need to ask and adjust as part of perioperative care.

The American Society of Regional Anesthesia and Pain Medicine (ASRA) released new guidelines in early 2023 on the management of perioperative patients on cannabis and cannabinoids.¹ Developed in response to the increased use of cannabis and concerns that it potentially can interact with anesthesia and lead to complications, the guidelines were designed to help clinicians make evidence-based decisions regarding the management of surgical patients who consume cannabis, whether medicinally or recreationally.

Universal Screening Is Recommended, Toxicology Screening Is Not

As a part of standard pre-anesthesia care, the guidelines recommend that all patients be screened for cannabis use during the preoperative evaluation. Further, because cannabis intoxication can be detrimental in the perioperative period, perioperative physicians should evaluate patients for acute intoxication and be aware of cannabinoid interactions with other medications, anesthetics, and physiologic changes.

Smoking Prior to Elective Surgery Increases Risks

In addition to screening patients for cannabis use prior to surgery, clinicians should counsel patients on the potential risks of continued perioperative cannabinoids. When cannabinoids are used, patients experience increased tachycardia and hypertension, increasing their risk of experiencing myocardial infarction. What’s more, a nationwide retrospective database study has shown that there was a 60% increase in hospital mortality among marijuana users managed for acute myocardial infarction.⁴

Given the increased risk to patients, the guidelines recommend delaying elective surgery for a minimum of two hours after cannabis smoking and postponing elective surgery in patients who have an altered mental status due to cannabis intoxication.

According to Benedict Alter, MD, PhD, an anesthesiologist and director of translational pain research in the division of pain medicine at University of Pittsburgh Medical Center St. Margaret, acute cannabis use immediately prior to surgery increases heart rate and impacts blood pressure. In an interview with the Pittsburgh Post-Gazette, Dr. Alter urged patients to think of disclosing their cannabis use like they would any other medical issue, noting that doctors are not required to report cannabis use and that patients won’t get into legal trouble for disclosing their cannabis use.⁵

Pregnant Patients Should Receive Special Counseling

Due to a number of specific pregnancy-related concerns, the new guidelines recommend that pregnant patients be educated and counseled about the risks of maternal cannabis use on the fetus/neonate; and, further, that cannabis use during pregnancy and during the immediate postpartum period be discouraged.

According to a 2019 survey by the Substance Abuse and Mental Health Services Administration (SAMHSA), approximately 8% of women utilize marijuana during their pregnancies.⁶ Because cannabinoids can affect both maternal and fetal physiology, readily crossing the placenta, anesthesiologists must be familiar with the physiologic effects, interactions, and safety concerns specific to pregnancy.

Cannabinoids may impact, among other things, fetal brain development, pre-eclampsia (a hypertensive disorder), and postoperative hypothermia. However, the ASRA guidelines make it clear that there is no currently available evidence that suggests any specific implications with neuraxial anesthesia for labor or cesarean section.

Perhaps the primary issue for anesthesiologists caring for patients with exposure to cannabinoids is determining which adjustments, if any, are needed with respect to dosages of routine medication, whether ventilator settings should be adjusted, and whether these patients require any special postoperative considerations.

While evidence is limited in these areas, the guidelines suggest that the timing of a patient’s last cannabis consumption may have an effect on lowering anesthetic requirements in the acutely intoxicated user but increasing anesthetic requirements in the long-term regular user. Further, despite the effects of cannabis on heart rate and blood pressure, there is insufficient evidence to recommend for or against the use of intraoperative EEG monitoring in patients who have taken cannabinoids.

Related to ventilator use, limited studies suggest that patients who consume cannabis orally (edible marijuana products) do not need any special adjustments, but that adjustments should be considered in patients who chronically consume cannabis via inhalation. However, evidence is insufficient to guide adjustments to ventilation settings.

Co-Administration of Opioids and THC Does Not Increase Adverse Events

Chronic pain is one of the most common indications for medical cannabis prescriptions, and a number of preclinical studies have found a synergistic effect between cannabis and opioids in patients with chronic pain.⁷ Because both cannabis and opioids are commonly used for pain management, and often together, it naturally follows that providers are concerned with if, and how, these substances interact with one another in the preoperative, perioperative, and postoperative settings. While evidence is lacking in this area, no available studies revealed any increase in significant adverse events (moderate to severe respiratory depression, nausea, or vomiting) during co-administration of THC and opioids. However, there is limited evidence that suggests possible increased pain and opioids requirements in postoperative patients who use cannabis.

Cannabis Withdrawal Symptoms Should Be Managed Postoperatively

The new guidelines warn that cannabis withdrawal symptoms can occur in the postoperative period, including irritability or anger, anxiety, insomnia, decreased appetite, restlessness, altered mood, and physical symptoms causing significant discomfort, such as abdominal pain, tremors, sweating, fever, chills, or headache. Cannabis withdrawal is common in cannabis users during this period, as the associated symptoms often occur 24 to 72 hours after cannabis cessation, peak in the first week, and can last up to two weeks-and thus coincide with the postoperative recovery period for those who used cannabis in the timeframe leading up to their surgical procedure.

The new guidelines from ASRA acknowledge that the medical, social, and political landscape of cannabis use is fluid and changing at a rapid pace. In accordance with the National Academy of Medicine’s standards for developing clinical practice guidelines, the ASRA Pain Medicine task force has pledged to continue monitoring the evolving science and will revise the guidelines as new evidence becomes available.

  1. Shah S, Schwenk ES, Sondekoppam RV, et al. ASRA pain medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids Reg Anesth Pain Med. 2023;0:1–21. doi:10.1136/rapm-2022-104013
  2. Shah S, Schwenk ES, Sondekoppam RV, et al. ASRA Pain Medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids. Regional Anesthesia Pain Medicine. 2023;48:97-117.
  3. Adamson SJ, Kay-Lambkin FJ, Baker AL, et al. An improved brief measure of cannabis misuse: the cannabis use disorders identification Test-Revised (CUDIT-R). Drug Alcohol Depend 2010;110:137–143. doi:10.1016/j.drugalcdep.2010.02.017
  4. Patel RS, Katta SR, Patel R, et al. Cannabis use disorder in young adults with acute myocardial infarction: trend inpatient study from 2010 to 2014 in the United States. Cureus 2018;10:e3241. v doi:10.7759/cureus.3241
  5. Webster H. Cannabis interactions prompt new guidelines from anesthesiologists. Pittsburgh Post-Gazette. January 14, 2023. Available at: Accessed February 8, 2023.
  6. SAHMSA. Key substance use and mental health indicators in the United States: results from the 2019 national survey on drug use and health, 2020. Available at: Accessed February 2023.
  7. Nielsen S, Picco L, Murnion B, et al. Opioid-sparing effect of cannabinoids for analgesia: an updated systematic review and meta-analysis of preclinical and clinical studies. Neuropsychopharmacology. 2022;47(7):1315-1330. doi:10.1038/s41386-022-01322-4.
  8. Allsop DJ, Norberg MM, Copeland J, et al. The Cannabis Withdrawal Scale development: patterns and predictors of cannabis withdrawal and distress. Drug Alcohol Dependence. 2011;119(1-2):123-129.