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Cannabis Dependence Linked to Post-Surgery Complications, Study Finds

By Alexander Beadle

Published: Oct 24, 2022   

Image credit: Artur Tumasjan via Unsplash

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People who are dependent on cannabis tend to have higher rates of infection following knee and shoulder keyhole surgeries, a new study has found.

Presented at the Scientific Forum of the American College of Surgeons (ACS) Clinical Congress 2022, the researchers say their findings are likely to be applicable to more invasive surgeries. They also believe that surgeons and healthcare providers should be discussing cannabis use with pre-operative patients alongside other known risk factors, such as tobacco use.

Patients with cannabis dependence had higher rates of complication

To investigate the effects of cannabis dependence on surgical outcomes, the study researchers retrospectively searched PearlDiver, a national insurance claims database. They found a total of 1,113,944 million knee arthroscopy and 747,938 shoulder arthroscopy patient records. Arthroscopy is a minimally invasive surgical procedure for checking and repairing joints where only small keyhole incisions are needed.

Of the approximately 1.86 million patient records included in this study, a total of 21,823 patients also had a diagnostic code for cannabis dependence on their medical record. By examining the cohorts with and without this diagnostic code, the researchers were able to evaluate whether there were any changes to the risk of developing common postoperative complications, including infection, deep vein thrombosis (DVT), or pulmonary embolism (PE).

They found that in both the knee and shoulder surgery subgroups, the cohort with diagnosed cannabis dependence experienced higher rates of infection and DVT compared to their peers. However, the rates of postoperative PE were comparable across both cohorts.

In the shoulder arthroscopy group, postoperative infection rates rose from 0.7% to 1.7% in the cannabis dependence cohort, while the DVT rate doubled from 0.2% to 0.4%. Similar increases were seen in the knee surgery group, where infection rates rose from 1.1% to 2.6%. A small increase was also seen in the DVT rate, which rose from 0.2% to 0.3% in the cannabis dependence cohort.

“Marijuana has been gaining so much popularity, but it’s a risk factor we aren’t really catching,” lead study author Sarah Bhattacharjee said in a statement. Bhattacharjee conducted the research while a medical student at the University of Chicago. She is now a surgical resident in orthopedic and sports medicine at the University of Washington.

“The higher infection rate found by this new study should raise a ‘red flag’ for patients and providers and should be discussed along with other risk factors before an arthroscopic procedure,” Bhattacharjee said.

Cannabis dependence is a risk factor for infection

In addition to assessing the difference in risk between those with a cannabis dependence and their peers, the researchers also carried out several multivariate analyses which controlled for a variety of other known patient risk factors, such as a history of diabetes or tobacco use.

They found that cannabis dependence was indeed an independent risk factor for postoperative infections for both the knee and shoulder arthroscopy groups. Based on this, the researchers say that more research on the nature of the relationship between cannabis dependence and postoperative complications is warranted.

Marijuana-Dependent Patients at Higher Risk for Infection | Clinical Congress | ACS. Courtesy of American College of Surgeons' YouTube channel.

“There’s so much information out there on smoking, alcohol, and other substances, but not on marijuana use,” study coauthor Jason Strelzow, assistant professor of orthopaedic surgery at the University of Chicago, said in a statement. “As providers and surgeons, we should be discussing marijuana use with our patients, something that we have traditionally shied away from.”

While the surgical procedures examined here were minimally invasive, Strelzow added that they “would expect similar or larger effects with more open or invasive procedures.”

The researchers also recognize that they used quite rigid criteria for determining cannabis dependence; the study relied on the presence of a formal medical diagnosis code on patient records. Wider research examining different self-reported cannabis use levels may also help to characterize the relationship between cannabis use and postoperative infection risk.

Cannabis and surgery

With the legal cannabis market predicted to experience massive growth throughout the next decade, it is important that cannabis is closely evaluated to determine whether it may be an additional risk factor in medical settings.

Previous research on patients receiving surgery for a broken shin bone has indicated that cannabis users tend to require more anesthesia during surgery compared to non-users. Patients in this study also reported higher levels of pain following the operation and received higher doses of opioid pain medications while recovering on the hospital ward.

Another study, this time on patients undergoing major orthopedic surgery, also found evidence to suggest that preoperative cannabis use was associated with greater pain intensity following the procedure. The patients who used cannabis in this study also tended to report poorer sleep outcomes during recovery.

On the face of things, it may seem odd that a drug that has been associated with pain relief in chronic pain would be so problematic when it comes to acute post-surgical pain. But could this be down to the type of cannabis being used? A new phase 3 clinical trial, planned to be completed in 2024, aims to investigate just that.

The trial will compare the effects of CBD-dominant cannabis versus placebo during patients’ recovery from a total knee replacement procedure. While many recreational cannabis strains are seen as more desirable for having higher levels of intoxicating THC, CBD’s analgesic and anti-inflammatory properties have made CBD-dominant strains an interesting target for therapeutic studies.


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