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Cannabis users need 220% more anesthesia to undergo surgery, study finds 

Cannabis users need 220% more anesthesia to undergo surgery, study finds

  • The report comes from a small study of 250 surgery patients in Colorado
  • Marijuana has been legal medically and recreationally in Colorado since 2012
  • The researchers found a need for more anesthesia in patients who regularly used marijuana 

Cannabis users need more than triple the anesthetic to undergo surgery, according to a new study.

The report, from a small study of 250 surgery patients in Colorado, found the normal dose of anesthesia was less effective in those who consumed marijuana on a weekly or daily basis.

Since 1980, anesthetists have warned people to abstain from marijuana weeks before surgery because the risks are unclear, and last year the American Association of Nurse Anesthetists issued another warning to that effect.

But researchers are now racing to understand exactly what those risks are as the drug becomes ubiquitous, with legal medical marijuana in more than half the US.  

The report comes from a small study of 250 surgery patients in Colorado, where marijuana has been legal medically and recreationally since 2012

The research team in Colorado, where marijuana has been legal medically and recreationally since 2012, examined the medical records of 250 patients who had endoscopic procedures after 2012.

These procedures involve a camera on the end of a long, thin tube being inserted into the mouth (a gastroscopy) or the bottom (a colonoscopy). It can also be inserted via a small cut made in the skin during keyhole surgery.

Researchers found that patients who smoked or ingested cannabis on a daily or weekly basis required more than three times more propofol, a common anesthetic, to relax.

They looked at two other anesthetic drugs and found that patients required 14 percent more fentanyl and 20 percent more midazolam to achieve optimum sedation for routine procedures, including colonoscopies.

Lead researcher Dr Mark Twardowski said colleagues in nearby emergency departments say more patients are complaining of chronic nausea, a symptom of regular cannabis use.

He also said that colleagues in anesthesiology have found that cannabis users require much higher dosages of drugs to send them to sleep and have higher rates of seizures after their operation.  

Cannabis use in the US has increased by 43 percent between 2007 and 2015. An estimated 13.5 percent of adults used it during this period.

As more countries legalize cannabis, researchers say people are more willing to admit to using it. This means they will be more likely to answer questions by a medical professional so data can be collected about its effects.

Putting questions about cannabis on patient forms is the first step to getting useful information that influences patient care, according to scientists.

Dr Twardowski, an osteopathic internal medicine physician, said: ‘Some of the sedative medications have dose-dependent side effects meaning the higher the dose, the greater likelihood for problems.

‘That becomes particularly dangerous when suppressed respiratory function is a known side effect.

‘Cannabis has some metabolic effects we don’t understand and patients need to know that their cannabis use might make other medications less effective.

‘We’re seeing some problematic trends anecdotally and there is virtually no formal data to provide a sense of scale or suggest any evidence-based protocols.’

He added: ‘This study really marks a small first step.

‘We still don’t understand the mechanism behind the need for higher dosages, which is important to finding better care management solutions.’

Dr Twardowski’s team is developing a follow-up study on different sedation requirements and anesthesia as well as post-procedure pain management for regular cannabis users compared to non-users.

The findings were published in The Journal of the American Osteopathic Association.


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