Marijuana’s most common method of use is by smoking. For that reason, the primary anesthesia implications will be based on that method of use.

Airway affects – bronchodilation happens short-term, but chronic cough, upper airway edema, and airway obstruction can result from regular smoking. If smoked regularly, airway reactivity becomes similar to that of tobacco smokers.

Hemodynamics – shown to reliably cause tachycardia, vasodilation, and postural hypotension. One study noted a fivefold increased risk of myocardial infarction (MI) in the first hour following cannabis smoking compared to a 24-fold increased risk of MI in the hour following cocaine ingestion. The risk of MI rapidly decreases one hour after use.

Drugs – nondepolarizing muscle relaxants and norepinephrine are potentiated. Drugs that cause cardiac and respiratory depression are augmented. Profound response to inhaled anesthetics. Dexamethasone can be used to reduce airway edema. Avoid drugs that affect heart rate (ie. Robinul, epinephrine, atropine, ketamine).

Central nervous system – anxiolysis, relaxation, euphoria, memory dysfunction, analgesia. Deficits in reward processing (apathy and amotivation) are also observed. In some (primarily regular users of marijuana), increases can be seen in anxiety, paranoia, and psychosis

GI – Antinausea, abdominal pain

Withdrawal – can begin within a day for high-dose chronic users and can take weeks to resolve. The symptoms will be exacerbated postoperatively if the patient is in withdrawal – so make sure to question the frequency and amount the patient is regularly using. Symptoms of withdrawal include irritability, aggression, anxiety, nervousness, insomnia, disturbed dreams, depression, anorexia, weight loss, abdominal cramping, tremors, fever, chills, and headache. There is no official treatment regimen for withdrawal, though benzodiazepines and synthetic THC ( commonly used to treat nausea in patients being treated with chemotherapy ) have been shown to be effective. Symptoms can mimic malignant hyperthermia, serotonin syndrome, neuroleptic malignant syndrome, 3,4-methylenedioxymethamphetamine overdose, or thyrotoxicosis.

Drug test – detection window is 7 days, 2 months with chronic abuse. Level of intoxication is best assessed by a thorough history and physical – do not rely on the drug test. Dronabinol and sulindac can produce false positives.

Substance abuse (general considerations) – If necessary, get your urine/blood screen early. The urine screen will take 30 minutes and a serum screen will be closer to an hour. Almost all drug screens will return results for marijuana, amphetamines/methamphetamines, phencyclidine (PCP), cocaine, opioids, barbiturates, and benzodiazepines. Generally speaking, if the patient is acutely intoxicated, the case should be cancelled/delayed. Refer to your facility to get policies on cancellations/delays.

Marijuana a form of cannabinoid and is the most commonly abused illicit drug. Cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) are the two major cannabinoid compounds in marijuana responsible for the affects. THC is responsible for the affects of euphoria. Cannabinoid affects are seen in nociception, anxiolysis, memory, cognition, emotion, and movement with a relative sparing of respiratory depression. Important to note, however, that there are hundreds of cannabinoid compounds in marijuana, all of which have their own affects.

Lipid solubility – highly lipid soluble. Affects will be seen within seconds to minutes when smoking.

Metabolism – Hepatic metabolism. Metabolism results in multiple psychoactive and nonpsychoactive metabolites. Eliminated through urine, bile and feces. Half life is 20-30 hours. Tissue half life, however, may last as long as 30 days, which makes it difficult to assess the level of intoxication.