Effects of Preoperative Marijuana Use on Anesthesia

Susan Elczyna CRNA, PhD

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Have you ever smoked Pot?

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Marijuana

!2727 B.C. – Chinese Emperor Shen Nung !Greek, Roman Empires ! Islamic Empires, North Africa and Middle

East !Western hemisphere by Spanish !Originally used as fiber – hemp

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Marijuana

!North America – recreational use

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Adult Marijuana Use by state
2017-2018

1.Oregon 28.5% 2.Colorado 3.D.C. 4.Vermont 5.Maine

6.Alaska 7. Washington 8. Nevada 9. Rhode Island 10. New Hampshire 20.9%

NY = 21 – 15.3% PA = 27 - 14.4%

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Who is using marijuana?

The BOOMERS

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CDC

!Different age groups from 2002 to 2014 !Use among ages 55 to 64 years old rose

45% !Usage rate for those between 18- and

25-years old only rose 10%.

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Medical Uses

! Immunosuppressant !Muscle relaxant !Anti-inflammatory

agent !Appetite modulator !Antidepressant

!Anti – emetic !Bronchodilator !Neuroleptic !Antineoplastic !Anti-allergan

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Endocanniboid System 
2 G-protein-coupled receptors


CB1! psychoactive potential ! expressed in:

! CNS

! GI tract

! Adipocytes

! Liver tissue

! Skeletal muscle

CB2! More restricted in

distribution: ! Expressed in:

! Immune cells in tonsils, thymus, spleen and bone marrow

! Enteric nervous system

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Endocannibinoids

!Receptors activated by: !AEA – anadamide !2-AG – 2- arachidonoylglycerol

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Endocannabinoids

!Cannabinoid binding regulates presynaptic Calcium levels

!Reduced release of neurotransmitters !Essential role in homeostasis –

neuroendocrine system

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THE FACTS

!Cannabinoid receptors are the most abundant of neuro-modulatory receptors to be found within the body

!All creatures, both with and without a backbone, have an endocannabinoid system

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THE FACTS!ECS regulates homeostasis !Diet and exercise boosts the ECS

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Cannabis

!Phytocannabinoids - Medicinal properties !Mimic endocannibinoids !THC & Delta 9 THC - CB1 ! Delta 9 (most abundant ) and Delta 8

THC – most potent psychoactive cannabinoids

!Cannabidiol (CBD) – CB210/1/2020 21

THC and CBD effects

!depend on the species, strain, cultivation, and storage of the plant

1.C. sativa 2.C. indica 3.C. ruderalis

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Cannabis Sativa

! Hemp plants !Tetrahydrocannabinol (THC)

! Hashish !Powdered form of plant’s resin, 7-12% THC

! Ganja, sinsemilla: !Dried tops, 5 - 8% THC

! Marijuana, bhang: !Remainder, 2 - 5 % THC

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THC

! Smoking – heat the plant to 800 degrees !Releases THCA !Turns to delta 9 THC

!Eating – Heat to 150 degrees !Activated THC (highly lipid soluble) !Dissolve in oil

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Pharmacology

! Pulmonary route most potent

! Pipes, cigarettes, water pipe minimizes acrid & irritating smoke

! Rapid effects

!Onset 15 minutes !Lasts 1-4 hours !4 times more tar >

tobacco cigs to lung

! Powdered hashish & marijuana mixed w/foods and ingested !Onset 90 min !Peak in 4-6 hrs !Duration 5-12 hrs !Hashish oil IV

!High mortality

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Pharmacokinetics! Peak within minutes of smoking ! THC metabolized by liver- 80+ metabolites

! Elimination route bile and feces

! Affect metabolism of other drugs – ! Ethyl alcohol, barbiturates, amphetamines, cocaine, opioids

! Elimination half-life ! THC 10-13 days

! Some metabolites 50 hours to 6 days ! Positive urinalysis in heavy users for 1 month

! Accumulation dosing

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Pharmacokinetics

!THC in GI tract !Metabolized by Liver !11 - OH-THC !More potent than THC !Use less plant !Difficult to determine content of THC

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Pharmacodynamics

!Binding to receptor causes a disruptive effect on the cell membrane

!May inhibit K+channels & glutamate release

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Effects

Low doses! Increased sympathetic

activity ! Increased beta

adrenergic activity ! Tachycardia, HTN ! PVCs ! EKG changes

High doses ! CB1 receptors ! Parasympathetic

activity ! Bradycardia ! AV block ! Hypotension

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Myocardial events! Increase as THC content increases ! Sensitization of myocardium to epinephrine ! Increased carboxyhemoglobin ! Increased myocardial O2 demand ! Decreased O2 supply ! Induced platelet aggregation ! Study of 1913 adults – previous MI had 4X the death rate

if use > 1/wk

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Stroke

! Ischemic strokes most common vascular side effect !Young age (30-50) !Male gender 3.7:1 !Chronic users

! BP swings !Cerebral vasoconstriction !Drug induced vasospasm

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Pre-op evaluation! History:

! Previous use, route of administration, last use and adverse effects ! Acute vs long term use

! Preop urine – may be positive up to 30 days after use ! Lower threshold for advanced cardiac testing

! Highest risk for CV events when acutely intoxicated with marijuana – delay surgery

! Warfarin metabolism inhibited by hepatic effects of cannabis, increased chance of bleeding, regional anesthesia implications

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Pre-op

!Chronic users abstaining for surgery !Withdrawal symptoms !Anger, anxiety, agitation, aggression,

nausea, muscle cramps !Increase in symptoms of condition

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Major periop findings in users

New Users! Tachycardia ! Systolic hypertension ! Malignant arrhythmias ! Coronary spasm ! Airway hyperactivity ! Uvulitis

Chronic users! Bradycardia/tachycardia

! Postural orthostatic hypotension

! Sinus arrest

! Hyperreactive airway

! Hypothermia

! Coronary vasospasm, MI

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Intraoperative considerations

!Respiratory system !Same as smokers !Hyperresponsiveness to airway stimulation

!Consider dexamethasone !Avoid histamine releasing substances !Delay surgery 72hours

!Spontaneous pneumothorax !Bullous emphysema – PPV

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Intraoperatve considerations

!Uvular edema !Uvulitis

!Due to inhaling large quantities of marijuana 6-12 hrs preop

!Laryngospasm !Stimulation of Chemo and thermoreceptors

!Aspiration risk d/t slowed gastric emptying, RSI with ETT

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Intraoperative considerations

! Cannabis linked to decrease body temperature ! Hypothermia ! Shivering

!Tachycardia !Hypoxemia ! Increased O2 consumption !Myocardial ischemia !Acidosis

! Vasodilatation from inhaled anesthetics

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Drug Interactions

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Drug Interactions

! Receptor interactions - CB1, CB2

! Synergistic or antagonistic interactions ! Absorption, metabolism, distribution, excretion –

! Enzyme Cytochrome P450 system – induction takes several days to develop while inhibition is almost instantaneous

! THC and CBD – metabolized by CYP450 system

! Inhibits CYP3A, CYP2D6, CYP2C9, CYP1A1, 1B1, 2B6 (propofol breakdown), 2C19, 3A4, 2C8

! Inhibit/activates glucuronosyltransferases

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Drug interactions

!Propofol !Hypnotic ! anti-emetic properties !Enhances anandamide !Inhibits anandamide degrading enzyme – fatty

acid amide hydrolase !Hypotension - CB1 receptor mediated inhibition

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Propofol

!Study by Schelling et. al. !TIVA vs etomidate/Sevoflurane !Higher levels of Anandamide in TIVA group !Decreased level in Etomidate/Sevo group

!Possible reason for N/V with inhalationals

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Propofol!Cross-tolerance with chronic marijuana users, (both

affect Anandamide receptors) !Cytochrome P450 2B6 – responsible for oxidation of

propofol !LMA

!Increased doses to insert !Endoscopy

!Higher doses of both midazolam and propofol to complete procedure

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Effect on Anesthesia

!THC - Anticholinergic affect !Depletes acetylcholine stores !Potentiates NDMR !Atropine, Glycopyrrolate

!Sustained tachycardia

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Effects on Anesthesia

!Muscle relaxant properties !Potentiation of NDMR

!CV effects !Avoid Ketamine, Pancuronium, Atropine,

Epinephrine !Hemostasis

!Decreased platelet activation and aggregation

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Postoperative concerns

!Chronic marijuana users !Lower pain threshold to acute surgical pain !Increased opioid requirement !Withdrawal symptoms !Carboxyhemoglobin levels 5X higher in users,

decreased wound healing

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Grandma the Dealer

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