Some research has suggested that giving a patient ketamine may help prevent delirium and reduce pain after surgery, but a new study found the anesthetic drug doesn’t ease the pain and can even lead to nightmares among older adults.

The study, published in The Lancet, is timely, considering an increased number of patients are receiving the drug during surgery, study author George A. Mashour notes in a press release.

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“We wanted to test this in a larger cohort along with the outcome of delirium in patients at high risk,” Mashour said. “The two adverse outcomes are linked -- pain can cause delirium, but opioids, the usual treatment for pain, can also cause delirium. We reasoned that if ketamine could reduce pain and delirium, it would be an important advance.” But it didn't reduce either.

Delirium is very common among adults aged 65 years and older. The condition (not to be confused with dementia) is categorized by a state of confusion that quickly develops and generally goes away in days to weeks if properly treated, according to the American Delirium Society. It often happens after surgery, but it can be a result of infections, lack of sleep, and medications.

To study the effect on older adults’ delirium and pain from ketamine, the researchers studied more than 600 individuals at least age 60, all of whom underwent major surgery under general anesthesia. They were divided into three groups: placebo, low-dose ketamine, and high-dose ketamine. All of the participants’ delirium and pain levels were assessed six times in the few days following surgery.

The data revealed that ketamine didn’t reduce or increase delirium. More surprisingly, the researchers found that the drug didn’t reduce pain and use of opioids. But, co-investigator Phillip Vlisides notes the current study’s results may contradict prior findings because their study was much larger than previous ones in regards to pain, and had rigorous methodology.

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Additionally, they found that the patients who received higher doses of ketamine experienced greater negative effects. “Unfortunately, we also found that some of the known negative effects of ketamine, such as hallucinations and nightmares, were increased in dose-dependent ways,” Mashour said.

The study authors recommend further research be conducted to better evaluate the drug. Some previous studies on ketamine have found that low-doses of the drug show promising results for those with severe depression and may possibly treat patients within hours or even minutes. While this finding was discovered more than a decade ago, the drug is still not approved for depression treatment; however, many doctors prescribe it off-label.

See also: Depressed People Who Express Suicidal Thoughts Find Relief In IV Ketamine Treatment

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