Page 31 - CASA Bulletin of Anesthesiology 2022; 9(5)
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Vol. 9, No 5, 2022
Induction & Maintenance
Multiple studies have described an increased requirement of several anesthetic medications
in patients with chronic cannabis use. The relevant mechanisms of action shared by perioperative
medications and cannabinoids are through opioid, GABA, and NMDA receptors, thereby
resulting in a potential for drug interactions.
A 2009 prospective, small sample size, human study found that chronic cannabis use
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increased the propofol dose required for induction when inserting a laryngeal mask . More
recently, a retrospective cohort study with 250 patients determined that regular cannabis use had
a significant effect on the amount of sedation required, with cannabis users requiring 14% more
fentanyl, 19.6% more midazolam, and 220.5% more propofol for the duration of the endoscopic
procedure .
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For inhaled anesthetics, a retrospective study demonstrated an increased delivery of
intraoperative inhaled anesthetic among preoperative cannabis users, which may be due to
increased tolerance . This finding of a significantly greater sevoflurane requirement in cannabis
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users is consistent with other studies that demonstrated a link between cannabis use and a higher
tolerance of inhaled anesthetics, such as isoflurane 33-34 .
Therefore, anesthesia providers should be prepared to administer increased dosages of
induction and maintenance anesthetic agents in patients with chronic cannabis use. These
patients may also benefit from more rigorous monitoring as the interpretation of heart rate and
blood pressure as factors in the determination of anesthetic depth may be complicated by the
cardiovascular effects of cannabis .
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PONV, acute pain, and withdrawal
Three postoperative considerations for chronic cannabis users include postoperative nausea
and vomiting (PONV), acute pain, and cannabis withdrawal syndrome.
Chemotherapy-induced nausea and vomiting is an accepted indication for medicinal cannabis
depending on state legislature, however studies have shown not shown cannabis to be useful in
the prevention of PONV 35-37 . Cannabis use can even result in severe refractory cyclic nausea and
vomiting, termed cannabis hyperemesis syndrome. In a retrospective analysis, daily cannabis
users were found to have an increased risk of PONV, however another study found no difference
in the rate of PONV among chronic cannabis users and cannabis naïve patients 38-39 . Ladha et al.
found limited evidence in support of additional PONV prophylaxis for cannabis users, though the
authors ultimately determined that the potential benefit outweighed the risks and stated that
additional PONV prophylaxis is unlikely to result in harm .
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Chronic pain is another accepted indication for medicinal cannabis depending on state
legislature because cannabinoid effects on CB2 receptors in the dorsal horn have been shown to
cause a reduction in inflammation and the modulation of pain . However, cannabis has not been
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demonstrated to be useful in the acute, postoperative pain setting. Due to the close linkage
between the cannabinoid and opioid systems, chronic cannabis use may result in difficulties in
postoperative management of pain. The literature describing postoperative pain in cannabis users
yields mixed results. Multiple studies indicated greater pain and opioid requirements, while
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