In this retrospective chart review, no statistically significant differences were found in pre-operative or intra-operative anesthetic use, duration of surgery, post-operative narcotic use, or adverse events for cannabis users compared to cannabis non-users.

Cannabis users and non-users had similar peri-operative and post-operative outcomes. There was no significant difference between groups in intra-operative blood loss or post-operative complications. The incidence of adverse events, including wound breakdown, skin necrosis, and capsular contracture requiring re-operation, did not differ significantly between the cannabis user and non-user groups. Previous research demonstrates an association between cannabis abuse, formally known as cannabis use disorder, and increased peri-operative complications, such as thromboembolism and respiratory complications. Post-operative complications of cannabis use disorder include sepsis or septicemia, neurological complications such as anoxic brain injury and stroke, increased lengths of stay, and higher hospitalization charges [11]. Chronic cannabis use is also associated with similar pulmonary complications as tobacco inhalation, including airway inflammation. Furthermore, the use of cannabis within 72 hours of general anesthesia is advised against, as it can increase cardiac workload, may cause airway obstruction, may necessitate higher anesthetic dosages in the laryngeal airways, and increases the risk of stroke and myocardial infarctions [12].

The data compiled from this review did not indicate whether patients were chronic cannabis users or diagnosed with cannabis use disorder. However, the findings did not demonstrate significant differences between groups with regard to peri-operative complications, which indicates that cannabis use disorder may not have been present for the patients surveyed. This observation also suggests that the frequency of cannabis use and pathological responses to cannabis may increase susceptibility to peri-, intra-, and post-operative complications.

Cannabis use continues to be an increasing trend in the United States. An analysis of data from over 16,000 women ages 18 to 44 in 12 US states found that 9.9% reported current cannabis use [13]. Although a common occurrence, cannabis use is not without significant risk in certain patient populations. A prior retrospective study of 27,306 patients found that post-operative myocardial infarction rates were increased in patients with cannabis use disorder who underwent orthopedic, cardiac, obstetric, and general surgery-based procedures. However, there was no difference in the rates of peri-operative morbidity, mortality, length of stay, or costs [14]. Concerning pain management, prior studies have shown that chronic cannabis consumption may worsen post-operative pain, increase post-operative opioid use, and precipitate the development of post-operative hyperalgesia [15]. However, in our investigation, peri-operative anesthetic and post-operative narcotic requirements did not differ significantly between the cannabis user and non-user groups.

The American Society of Regional Anesthesia and Pain Medicine guidelines recommend universal pre-operative screening of patients for cannabinoid consumption, including the type of product consumed, time of last consumption, route of administration, amount, and frequency of use. The guidelines recommend delaying elective surgery for a minimum of two hours after a patient has smoked cannabis to minimize cardiovascular risks and ensure patients are able to provide informed consent [15].

Limitations

While this study provided important information on the impact of pre-operative cannabis consumption in EPBA, it is not without noted limitations to discuss. One of the main limitations of the retrospective nature of this review due to self-reported cannabis use is potential recall bias, as it may have been difficult for the patients to accurately remember the frequency or dose of cannabis used in the past. Another important limitation was the lack of reported specifics on the timing, dose, and form of cannabis consumed prior to surgery. Additional limitations that introduced possible inaccuracies and biases included incomplete data on the frequency and type of cannabis used regularly, uncontrolled confounders, such as diet or exercise, and whether cannabis was used for medical purposes or solely as a recreational drug. Furthermore, dose, dosage form, and route of administration could cause distinct effects, such as potential differences in smoking versus other dosage forms on pulmonary function. The route of cannabis administration, which can be oral, smoked, or vaporized, alters cannabis pharmacokinetics as well as its subjective and cardiorespiratory effects. These are important factors to take into consideration for future research. In addition, cannabis inhalation demonstrates faster peak blood plasma levels and higher bioavailability compared to the consumption of cannabis edibles or oil. Therefore, the comparison of patients who prefer inhalation rather than oral consumption may provide important data regarding the effect of cannabis use on surgical outcomes.

The absence of cannabis-specific patient information such as product type, frequency, and consumption route (inhalation vs. oral ingestion) limited the ability to directly ascertain whether cannabis use alone had a direct impact on peri- and post-operative outcomes, warranting further study with comprehensive data for cannabis users. Another limitation to consider is the lack of generalizability of the results due to the use of a single site with a single provider and the small sample size of 134 patients.

Despite expanding societal acceptance, especially in California, stigmatization of cannabis use remains a barrier to patient self-reporting. Surveys of cannabis consumers have shown that patients experience high rates of hesitation in disclosing cannabis use to healthcare providers, including fear of judgment, loss of employment, and legal repercussions [16]. Therefore, the limited data obtained from self-reports may be attributed to the ongoing stigmatization of cannabis use as opposed to recall bias.