Marijuana may interfere with pain control and the amount of pain medication needed after an operation.

1. Anesthesia Implications in
Cannabis Users
Hooman Rowshan, M.D. MSc

2. General Considerations
• Marijuana use has implications for pain management during surgery
• Studies have indicated the need for increased induction doses of
propofol and higher doses of inhalational agents in habitual
marijuana users
• Marijuana use has implications for pain management during surgery
• Patients who used marijuana preoperatively reported higher levels of
pain
• Marijuana use is legalized in many jurisdiction. Questions regarding
THC use should be the normal part of perioperative hx by the
ansthesia team

3. Pharmacology
• There are different types of cannabis, including Cannabis indica and
Cannabis sativa hybrid
• Limited research exists on specific strains for pain relief, and strain-
specific recommendations have not been medically proven
• Anctotal evidence exists that users preferred indica strains for pain
management, sedation, and sleep, while sativa strains were chosen
for energy and mood improvement
• The key components studied for pain relief were cannabidiol (CBD)
and tetrahydrocannabinol (THC)

4. Pharmacology Continued
• THC is the psychoactive compound responsible for the “high”
associated with cannibis use
• CBD has been used to treat inflammation and chronic pain, as well as
to manage anxiety and insomnia
• Recent research suggests that some cannabis products containing
THC and CBD may help with the short-term improvement of chronic
• However, there are risks of sedation and dizziness, and more data on
their long-term impact are need
• Certainly! Cannabis may offer relief from chronic pain, but it is
essential to understand its effects and limitations

5. Administration Methods
• Consuming cannabis-infused edible
• Applying lotions, balms, or salves containing cannabinoids
• Extracting cannabis oil and taking it orally
• Vaping: Lung damage is a serious long-term side effect
• smoking Marijuna cigareets. The long-term lung damage is a side
effect
• The pharmacokinetics can be variable depending on the method of
administration

6. Neurobiological Pathways
• THC activates receptors in the brain and nervous system, which helps
regulate pain
• THC also interacts with receptors on immune system cells, influencing
inflammation and the immune response
• Interestingly, research suggests that a cannabis placebo (designed to
mimic the real thing) provides pain relief similar that to of a cannabis-
based product
• The placebo effect involves the release of neurotransmitters,
including endocannabinoids, which structurally resemble active
compounds in cannabis.

7. Neurobiological Pathways Continued
• Expectation plays a significant role in the placebo effect. When
patients believe a treatment will improve their condition, it often
becomes a self-fulfilling prophecy.
• Placebos and active medications have physiological effects but work
through different neurobiological pathways
• Although the exact triggers for neurotransmitter release remain
somewhat mysterious, the brain responds to placebos by activating
pathways similar to those affected by THC2.

8. Cannabinoids in Cannabis
• The cannabis plant contains over 500 compounds, including
cannabinoids like delta-9-tetrahydrocannabinol (THC) and cannabidiol
(CBD)
• Marijuana refers to all products derived from the cannabis plant,
whereas marijuana specifically denotes parts of the plant (such as
dried leaves, flowers, stems, and seeds) containing substantial THC2
levels
• The strength of cannabis is measured by its THC concentration
• Over time, the potency of THC in marijuana has increased significantly

9. Cannabinoids in Cannabis Continued
• Sinsemilla, a more potent form of cannabis, contributes to this trend
• Marijuana extracts and resins now contain 3–5 times more THC than
the plant itself
• Cannabinoids bind to and act as partial agonists of two types of G-
coupled cannabinoid receptors, CB1 and CB2. CB1 receptors are
concentrated in the brain and nervous system tissue
• CB2 receptors are predominantly found in immune cells
• Activation of CB1 inhibits the release of several neurotransmitters,
affecting acetylcholine, L-glutamate, GABA, norepinephrine,
dopamine, and serotonin

10. Pharmacokinetics
• THC is quickly transferred from the lungs to the bloodstream during
smoking, and the onset of psychoactive effects occurs rapidly, within
seconds to minutes
• The psychoactive effects of THC from inhalation reach a maximum in
15 to 30 minutes and begin to taper off at 2–3 hours
• However, the duration of action may be up to four hours
• These effects mirror plasma THC concentrations
• A small amount of inhaled THC, approximately 2 to 3 mg, may
produce effects in a naïve user

11. Pharmacokinetics Continued
• Pulmonary bioavailability varies from 10 to 35 percent of an inhaled
dose
• Bioavailability in the lung is determined by by the depth of inhalation
along with the length of time of inhalation and breath-holding
• Smoking is the most common method of administration
• But Vaping appears on the rise
• Similar psychoactive effects are experienced through vaporization
although it may reduce exposure to by-products of combustion

12. Pharmacokinetics Continued
• Orally ingested cannabis has a later onset of action ranging from 60–
120 minutes
• Cannabis has low bioavailability because of degradation in gastric
acid and first-pass metabolism in the liver
• Orally ingested cannabis reaches its peak effect at approximately 120
minutes and can last up to 4 to 6 hours
• The elimination half-life of THC is difficult to measure and is slow,
with times ranging from 25 to 36 hours
• The slow-release occurs from lipid storage areas and enterohepatic
circulation.

13. Pharmacokinetics Continued
• The elimination half-life increases in regular cannabis users
• THC has high lipophilicity and distributes to highly perfused tissues. It
is also highly protein-bound (95 to 99 percent) mainly to lipoproteins
and has a volume of distribution of 2.5 to 3.0 L/kg
• THC is mainly metabolized in the liver through the P450 complex as
are many anesthesia drugs
• there is a potential for pharmacokinetic drug interactions through
either the inhibition or induction of these enzymes

14. Pharmacokinetic/ Pharmacodynamic Drug
Interactions With THC and Their Consequences
• Increased effects of clobazam, warfarin, hexobarbital
• Decreased effects of theophylline
• Additive pharmacodynamic effects with other agents having similar
physiological properties, such as sedation with CNS depressant drugs,
including benzodiazepines, opioids, and volatile agents
• Preoperative cannabis use may lead to tolerance to sevoflurane

15. Preoperative Issues
• it is important to take a good medical history, including the history of
cannabis use
• Anesthesia should consider the composition of the products used, a
history of adverse effects, the dose consumed, the effects caused by
missed doses, and the time since last exposure
• Understanding these factors is important in order to assess the risks
of cardiovascular and respiratory problems, and potential for
withdrawal symptoms
• risks associated with anesthesia administration during cannabis
intoxication

16. Preoperative Checklist
• Assess for signs of cannabis intoxication
• Evaluate for coagulation dysfunction ,for example, PTT, INR, and
platelet function tests
• Obtain history of angina and increased risk of coronary artery disease
• Consider delaying elective surgeries following acute patient
consumption of cannabis
• Symptoms of acute cannabis intoxication such as increased
anxiety,Paranoia, and Psychosis

17. Preoperative Checklist
• Patients with symptoms of acute cannabis intoxication are more likely
to emerge from anesthesia violently
• Among cannabis users who have a history of angina, it is important to
inquire about angina-free functional capacity during cannabis use
• In patients with an elevated risk of coronary artery disease, there is
an increased risk of myocardial infarction in the first hour following
the use of cannabis, and thus elective surgeries should be delayed by
at least one hour following cannabis use in these patients
• Preoperative cardiac function tests and cardiology consultation may
be required on case-by-case basis

18. Intraoperative Issues
• literature is lacking clinical guidance regarding intraoperative
anesthesia management in cannabis users
• Some research suggests that patients who regularly use cannabis may
require larger induction and maintenance doses of anesthesia
intraoperatively
• there may be an association between cannabis use and higher
intraoperative dose requirements of propofol to achieve adequate
sedation, but these claims have not yet been supported by well-
designed studies

19. Intraoperative Issues Continued
• A recent retrospective study assessing the impact of preoperative
cannabis use in patients undergoing open reduction and internal
fixation of tibia fractures specifically provided some evidence to
suggest minimal effect of preoperative cannabis use on anesthetic
dosing intraoperative
• there was no significant difference in total propofol,
dexmedetomidine, etomidate, ketamine, desflurane, midazolam, and
fentanyl doses administered between those who used cannabis prior
to surgery and those who did not
• he only agent for which there was a significant difference observed
between these two groups was sevoflurane,where the average total
volume of sevoflurane administered intraoperatively was significantly
higher among the group who used cannabis

20. Intraoperative Issues Continued
• Anesthesia professionals should take extra caution when using
intraoperative sympathomimetics and beta-blockers among those
using cannabis due to potential inhibition of CYP-45
• patients must be carefully monitored intraoperatively for signs of
hemodynamic instability and signs of myocardial infarction or stroke
• Anesthesia provider should be prepared to manage airway
hyperactivity intraoperatively if the patients do not have a secure
airway due to potential airway irritation caused by preoperative
cannabis use

21. Postoperative challenges
• There are two main challenges
• Management of postoperative pain
• management of withdrawal symptoms
• cannabis users are more likely to report higher pain scores, poorer
sleep, and require a greater quantity of analgesic medications in the
immediate postoperative period
• Multimodal analgesia and appropriate opioid dosing should be
considered
• Monitor cannabis users for signs and symptoms of withdrawal
postoperatively

22. Postoperative challenges Continue
• Withdrawal onset can take place within 1–2 days of the last cannabis
use and last 1–2 weeks
• Postoperative shivering, hypothermia, and increased platelet
aggregation have also been documented among cannabis users
• Postoperative hypothermia and shivering are thought to be mediated
by CB1 receptor activation and, thus, are not suspected to be due to
withdrawal symptoms
• High dose of THC increased platelet aggregation likely due to CB1 and
CB2 receptors existing on platelet membranes

23. Take Away Points
• The increasing use of cannabis, both medically and recreationally are
on the rise
• An estimated 9.5% of the United States adult population are cannabis
users
• Similar numbers are expected in Canada where cannabis is legal and
widely avaiable
• The use of medical cannabis is currently legal in 37 states, and
recreational cannabis use is legal in 18 states
• With the increasing prevalence of cannabis use among adults, it is
important that anesthesia professionals recognize the potential
cardiopulmonary, gastrointestinal, and central nervous system effects
of cannabis use