Cannabis dependence and abuse nearly doubled risk of heart attack post-surgery

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Cannabis dependence and abuse nearly doubled risk of heart attack post-surgery

Toronto, December 6, 2019

By Jennifer Stranges

Patients with active cannabis dependence and abuse were nearly twice as likely to suffer a heart attack after surgery, according to a study led by researchers at St. Michael’s Hospital of Unity Health Toronto.

The study, published in the Online First edition of Anesthesiology, the peer-reviewed medical journal of the American Society of Anesthesiologists (ASA), also found the prevalence of cannabis dependence or abuse recorded among surgical patients increased significantly over the last decade.

Researchers analyzed the records of more than four million adults in the United States from 2006 to 2015 undergoing one of 11 common elective procedures including knee or hip replacement, gallbladder removal, caesarian section, hysterectomy and hernia repair.

“While cannabis is often purported as being safe or benign, we don’t fully understand the health implications of this drug, particularly in heavy users,” said Dr. Karim Ladha, a clinician-scientist at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital and lead author of the study.

“The results of this study make it clear that we need to pay more attention to cannabis users undergoing surgery,” said Dr. Ladha.

Dr. Ladha noted that this research was the first step in determining whether there is any association between cannabis use disorders and perioperative outcomes. Dr. Ladha’s subsequent work will prospectively follow patients with self-reported cannabis use disorder undergoing surgery using a more detailed method of data collection to determine if the association persists.

The findings did not show a difference in overall outcomes between patients who had a cannabis use disorder and those who did not. However, in addition to increased cardiac risk, there was evidence that patients with cannabis use disorders were possibly at an increased risk for a stroke.

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the Hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

About Unity Health Toronto

Unity Health Toronto, comprised of Providence Healthcare, St. Joseph’s Health Centre and St. Michael’s Hospital, works to advance the health of everyone in our urban communities and beyond. Our health network serves patients, residents and clients across the full spectrum of care, spanning primary care, secondary community care, tertiary and quaternary care services to post-acute through rehabilitation, palliative care and long-term care, while investing in world-class research and education. For more information, visit

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