Cannabis Use Tied to Increased Pain After Surgery

By Megan Brooks

October 12, 2020

NEW YORK (Reuters Health) - People who use cannabis need more anesthesia during surgery and often have more pain and opioid use after surgery than non-users, new research indicates.

"I think the important takeaway from a clinical perspective is that we need to be specifically asking our surgery patients not only about alcohol and illicit substances, but also specifically for cannabis," lead researcher Dr. Ian Holmen, anesthesiology resident at the University of Colorado Hospital, in Aurora, told Reuters Health by phone.

Dr. Holmen presented the study October 5 during Anesthesiology 2020, the virtual annual meeting of the American Society of Anesthesiologists.

The researchers reviewed the electronic medical records of 118 patients (mean age, 44.5 years) who had surgery at the University of Colorado Hospital to repair a fractured tibia, including 30 cannabis users and 88 non-users. Data on the timing, frequency and type of cannabis use was not available.

Cannabis use (vs. non-use) was not significantly associated with a higher dose of induction propofol, according to the conference abstract. However, users required more sevoflurane during surgery (mean, 37.4 ml vs. 25 ml; P=0.023).

"This is really the first study that has shown that, for general anesthesia, the cruising phase, or the maintenance phase of anesthesia, requires more sevoflurane, which is an inhaled anesthetic that we use during this phase of anesthesia," Dr. Holmen told Reuters Health.

Cannabis users also had significantly higher pain scores while in recovery (mean, 5.8 vs. 4.8; P=0.009) and received 58% more opioids per day while hospitalized (155.9 vs. 98.6 morphine milligram equivalents per day; P=0.002), Dr. Holmen reported in his presentation.

"It's important to note that the study is a retrospective review, which on the scale of quality of the study is probably at the lowest end. So really, this is a hypothesis-driving study, and there needs to be significantly more research on this," Dr. Holmen told Reuters Health.

In the meantime, he said, "In Colorado, myself and I think a lot of other doctors are now specifically asking surgery patients about cannabis use," he added.

The risks of tobacco, e-cigarette and marijuana use before surgery were also the topic of a panel discussion this week during the American College of Surgeons (ACS) annual virtual meeting.

"Smoking remains one of the largest public health problems that we face in the United States. And there is good data to suggest that all patients should be quitting smoking prior to all non-emergent cases," said panel moderator Dr. Jonah Stulberg, general surgeon and health services researcher at Northwestern Memorial Hospital, in Chicago.

He noted that the risk of pneumonia nearly doubles in patients who undergo surgery while actively smoking and the risk of a heart attack is increased by nearly 70%.

"Whenever you inhale any type of substance, that increases the risk of respiratory complications," said panel member Dr. Thomas K. Varghese, Jr., a thoracic surgeon at University of Utah, in Salt Lake City.

Dr. Varghese is director of the ACS Strong for Surgery program (, which provides resources for patients, surgeons, and hospitals in surgery preparation. Currently, more than 330 hospitals around the country participate in the program.

"The biggest motivation a patient has is that they want their operation to go well. Many patients will do whatever is needed to make sure their surgery is a success. Surgeons can provide their patients with resources to be able to stop smoking and help create the environment that leads to success," Dr. Varghese commented in a conference statement.

SOURCE: Anesthesiology 2020, presented October 5, 2020.