GP3d - Do Cannabis Users Require More Anesthesia During Third Molar Removal Under Intravenous General Anesthesia When Compared to Non-Users?

Abstract: Statement of the problemConflicting evidence suggests patients who use cannabis and undergo intravenous general anesthesia (IVGA) for tooth extraction may have increased anesthetic needs.1,2 In addition, unlike tobacco and alcohol, there are no cutoffs to group cannabis consumption other than arbitrarily splitting users into daily, weekly, or monthly groups.The purpose of this study was to measure and compare the total milligrams (mg) of propofol (TMP) administered during IVGA for M3 removal with self-reported cannabis use (CU) and non-cannabis use (NCU). The investigators hypothesized that CUs would require more anesthetic drugs compared to NCUs. The specific aims were to: 1. Measure and compare CU vs. NCU with TMP delivered during IVGA; 2. Measure and compare CU vs. NCU with adjunctive anesthetic agents delivered during IVGA; and 3. Objectively identify cutoffs to group CU based on responses from a CU measurement questionnaire with TMP.Materials and methods:The authors implemented a prospective cohort study and enrolled a sample of subjects who were scheduled for M3 removal under IVGA between May 1, 2022, through February 28, 2023. Self-reported CU was measured using a modified “Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory (DFAQ-CU)” questionnaire, which uses a continuous scale to measure frequency and duration of CU. The independent variable was CU coded as yes (CU) and no (NCU). The primary outcome variable is TMP. Secondary outcome variables included mg of midazolam, micrograms (mcg) of fentanyl, mg bolus of propofol, propofol infusion (mg/kg/min), and mg of ketamine. Covariates included age, sex, American Society of Anesthesiologists classification, tobacco use, weight/BMI, Mallampati score, number of M3 removed, and anesthesia and procedure time. Descriptive and bivariate statistics were computed (P ≤ .05). Regression decision tree modeling was then used to split cannabis consumption based on responses from a CU measurement questionnaire with TMP.

Results: The sample included 49 subjects, 38 (77.6%) CU and 11 NCU (22.4%), with mean age of 26.7± 5.5 years, 61.2% female, and all ASA 1 or 2. Bivariate analysis showed significant increases in procedure time for CU compared to NCU (37.3 ± 14.1 vs. 32.3 ± 19.1, P = .04). Cannabis users, compared to NCU, were administered 55.5% more total propofol (225.5 mg ± 114.4 vs. 145 mg ± 102; P = .038), 60.7% more bolus propofol (107.4 mg vs. 66.8 mg; P = .02, and 20% less fentanyl (58.7mg vs. 70.6mg; P = .05) (Table 1). Differences in ketamine, midazolam, and infused propofol were not significant. Using responses from the questionnaire, the regression decision tree first split CUs based on duration, more or less than 2-3 years of use, and then frequency, more or less than multiples times a day. Those with less than 2-3 years use, representing 18% of the sample, were predicted to require 169 mg of propofol. Subjects with more than 2-3 years use, 82% of the sample, were then further split into two groups, CU less than multiple times a day (42%, predicted TMP 216 mg) or more than multiple times per day (39%, predicted TMP 262 mg) (Figure 1).

Conclusion: The results suggest that CUs require 55% more total propofol and increased procedure time in CU compared to NCU during IVGA for M3 removal. This study is the first to propose specific questions for identifying high-risk cannabis users undergoing IVGA, with our findings suggesting critical cutoffs for duration exceeding 2-3 years and a frequency of multiple daily use.

Bivariate analysis of anesthetic drugs stratified by CU
Figure 1. Regression decision tree based on total propofol (mg).