Cannabis hyperalgesia: A phenomenon underestimated in the peri-operatie period? Nassim Touil and Patricia Lavand’homme. European Journal of Anesthesiology. 2019. Article
Lena Yannella
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The Problem: According to a recent survey, patients generally believe that medical cannabis can be used to effectively manage pain, yet few studies have focused on the drug’s impact on postoperative outcomes.
Why do this study? Medical and recreational cannabis use is increasing. Many patients who are using cannabis are undergoing surgery, but it is not known what effect, if any, cannabis use might have on post-operative pain management.
The study: This paper is a commentary on an accompanying study in the same issue. That study focused on the effect of using recreational cannabis use prior to an abdominal surgery on post-operative pain management. It found that cannabis users needed a higher dosage of morphine to manage their pain than non-users. This commentary also points to another recent study by Liu et al., in which medical and recreational users of marijuana who underwent orthopedic surgery experienced more pain than non-users when consuming the same amount of opioids.
Conclusions: Both studies conclude that the use of cannabis and cannabinoids complicates postoperative pain management. More specifically, the use of cannabis prior to surgery appears to have some negative correlation with the effectiveness of opioids to treat pain. However, further research is needed to explore the relationship between the use of marijuana and the management of pain.
Funder: None
Author conflicts: None
Commentary (David Casarett MD): We included this commentary, rather than the original article, because it provides some important context and connects this study to others in the same vein. That’s important, because when these studies are considered together, it begins to seem as though cannabis users’ post-operative pain management is more complicated. That might be for physiologic reasons, as the authors suggest. For instance, it’s possible that cannabis use is associated with a modulation of the endocannabinoid system in ways that make patients more susceptible to painful stimuli, or more resistant to opioids, or both. However, it is also possible that surgical patients who are either medical or recreational cannabis users differ from non-users in important but unmeasured ways. They may also have other concomitant medical conditions, or perhaps other drug use. Taken together, these studies are clinically important, and suggest that cannabis use should be a warning flag for inadequate post-operative pain management. The question, though, is why that should be the case.
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