Archive April 2019 XX, No. 4

Safety: High Time to Address Marijuana

The dangers of patients smoking cannabis before surgery.

Sheldon Sones, RPh, FASCP

BIO

TOKING FOR TROUBLE
TOKING FOR TROUBLE Consuming cannabis before surgery can put patients at a higher risk for complications both during and after the procedure.

If you don't ask your patients if they smoke weed, you might want to start. As more states legalize both medicinal (33 states and D.C.) and recreational (10 states and D.C.) cannabis, you can expect to see an increasing number of pot-using patients. In 2017, 1 in 7 Americans had used marijuana, according to a report published in the Annals of Internal Medicine. Overall, 14.6% said they had used cannabis in the past year, while 8.7% said they had used the drug in the past 30 days. While research on marijuana use and its effects during surgery is limited, we know that cannabis has a number of pharmacologic implications.

1. Higher doses of sedatives. Be aware of patients who use marijuana as a self-prescribed sedative before surgery. The use of marijuana, especially immediately before surgery, can change the doses you'll need for sedation. A study (osmag.net/BF6kwN) in the March 2009 European Journal of Anaesthesiology found that patients who routinely use marijuana will require substantially higher doses of propofol for satisfactory clinical induction when inserting a laryngeal mask.

2. Vasodilation. Just like anesthesia, cannabis has a tendency to lower both blood pressure and heart rate. This will attenuate the effects of anesthesia, resulting in patients being under longer and having a harder time waking up.

3. Airway obstruction. Just like a nicotine smoker, pot smokers have an overactive airway, which can cause coughing and lead to aspiration during and after surgery. Smoking marijuana before surgery also increases mucus production in the respiratory tract.

4. Drowsiness. Marijuana might increase the amount of drowsiness some drugs cause. Examples include benzodiazepines such as lorazepam (Ativan) or diazepam (Valium), barbiturates such as phenobarbital, narcotics such as codeine, some antidepressants and alcohol.

5. Increased risk of bleeding. Marijuana may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin) or heparin, antiplatelet drugs such as clopidogrel (Plavix), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin, Advil) or naproxen (Naprosyn, Aleve).

6. Slow wound healing. The carbon monoxide in cannabis smoke inhibits blood oxygenation and decreases blood flow, which could lead to tissue death, more scarring and slower wound healing.

7. Blood sugar level changes. Marijuana could affect a patient's blood sugar levels, so exercise caution when patients are using both marijuana and diabetes medication (orally) or insulin.

Patient management

Your best safeguard is an extensive medication reconciliation that accounts for a patient's detailed marijuana usage — how often, what dosage, to treat which conditions? While there is far less of a stigma surrounding medical marijuana usage, some patients are less than honest about their own recreational use of the substance. As best you can, get an accurate medication reconciliation and be sure to highlight any marijuana usage for anesthesia providers, which can help them navigate through prudent and safe administration of intra- and post-procedure drugs.

Finally, stress to your pot-smoking patients that the sooner they can quit smoking before surgery, the better. With each passing smoke-free day, their overall risk of complications decreases. Quitting even 12 hours prior to surgery can make a difference, but quitting 8 weeks before surgery can have a dramatic impact on their surgery and recovery, particularly improving their response to anesthesia. OSM

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