January 06, 2022
Smoking marijuana may be risky after aneurysmal subarachnoid hemorrhage (aSAH).
A new study shows a significant association between cannabis use and delayed cerebral ischemia (DCI) after aneurysm rupture, with nearly three times the risk of DCI and poor functional outcome.
"Aneurysms are found in 3% of the population, but only a small fraction (approximately 1%) rupture per year. Therefore, our findings affect a small portion of the overall population," Michael T. Lawton, MD, senior author and president and CEO of Barrow Neurological Institute in Phoenix, Arizona, told Medscape Medical News.
"However, patients with a known aneurysm that is being managed conservatively with observation may want to reconsider their cannabis use in the event that their aneurysm ruptures," said Lawton.
The study was published online January 6 in Stroke.
Largest Study to Date
The researchers reviewed the records for all 1014 patients treated for aSAH at Barrow Neurological Institute over 12 years. All of them underwent urine toxicology screening on admission.
Overall, 367 patients (36.2%) had DCI, 509 (50.2%) had poor functional outcome (modified Rankin Scale score >2) and 137 (13.5%) died.
A total of 46 (4.5%) patients (mean age, 47 years; 41% women) had a positive urine test for tetrahydrocannabinol (THC), while 968 (mean age, 56 years; 71% women) tested negative for THC.
The rate of DCI was significantly higher in THC-positive aSAH patients than in peers who tested negative (52.2% vs 35.4%; P = .03).
A positive urine screen for THC reflects cannabis use within 3 days for a single use to within roughly 30 days for frequent heavy use.
In propensity score–adjusted binary logistic regression analysis, cannabis use was independently associated with an increased likelihood of DCI (odds ratio, 2.7; 95% CI, 1.4 – 5.2; P = .003).
A prior study found a similar relationship between cannabis use and DCI in 108 patients with aSAH.
"Our study confirmed this in the largest study to date in over 1000 patients," Lawton told Medscape Medical News.
Cocaine, methamphetamine, and tobacco use were not associated with DCI (P ≥ .29).
The study also showed a higher rate of angiographic vasospasm in cannabis users than nonusers (88.9% vs 70.5%; P = .008).
DCI was present in 50.0% of cannabis users with vasospasm vs 39.0% of nonusers (P = .17), which supports vasospasm as a potential reason for increased DCI, the researchers say.
"When people come in with ruptured aneurysms, and they have a history of cannabis use or are positive on a toxicology screen, it should raise a red flag to the treating team that they are at higher risk of vasospasm and ischemic complication," Lawton said in an AHA news release.
"Of all the substances detected in the toxicology screen, only cannabis raised the risk of delayed cerebral ischemia," he noted.
But the authors of an accompanying editorial in Stroke caution that more study is needed to determine the pathophysiology of cannabis-related cerebral ischemia.
"Ultimately, given the prior mixed results regarding the association of marijuana with cardiovascular complications, ischemic stroke or hemorrhagic stroke, it remains an open question whether cannabis precipitates cerebral ischemia via cerebral vasospasm and delayed cerebral ischemia," write Feras Akbik, MD, PhD, and Ofer Sadan, MD, PhD, with Emory University School of Medicine, Atlanta.
"Future studies should attempt to better quantify the cannabis exposure in terms of chronicity, dose and temporal relationship between the cannabis use and the aneurysm rupture event, in order to better understand whether indeed marijuana can precipitate cerebral ischemia," Akbik and Sadan say.
In the AHA news release, Robert L. Page II, PharmD, of the University of Colorado, Aurora, said the current study is not at the level of science of a randomized controlled trial, "but it is a rigorous statistical analysis involving more than 1000 patients, so the results are important and add to what we already know about possible adverse effects of marijuana use."
Page chaired the American Heart Association (AHA) 2020 scientific statement on medical marijuana, recreational cannabis and cardiovascular health.
The statement concluded that evidence for a link between cannabis use and cardiovascular health remains unsupported, and the potential risks outweigh any potential benefits.
The study had no funding. The authors and editorial writers have no relevant disclosures.