Ketamine was first introduced into clinical practice by investigators at the University of Michigan in the mid-1960s as a general anesthetic that could offer advantages, such as preserving breathing, not afforded by other anesthetic drugs at the time.
Since then, doctors have used the medication for other purposes.
“It’s an anesthetic but more recently has been found to have antidepressant and analgesic properties at lower doses,” says George A. Mashour, M.D., Ph.D., professor of anesthesiology, director of the Center for Consciousness Science and associate dean for clinical and translational research at the University of Michigan Medical School.
Mashour is the senior author of a new study published today, with an accompanying editorial, in The Lancet that sought to discover what effect ketamine has on delirium and pain — two serious postoperative complications.
Although the therapeutic connection has been affirmed before, analyses were limited in scope.
“Previous studies found evidence that ketamine could prevent delirium and reduce pain after surgery,” Mashour says. “However, these studies were often in small cohorts. We felt it was beneficial to test the effects of ketamine on delirium and pain in a multicenter, international study of older patients at risk who were undergoing major surgery.”
The new study also is driven by current medical practices. Mashour acknowledges that ketamine administration during surgery is increasing.
Which is why he and his close collaborator, Michael Avidan, MBBCh, professor of anesthesiology and cardiothoracic surgery at Washington University School of Medicine in St. Louis, sought to examine the drug’s supposed benefits more closely.
“Physicians have been increasingly using the drug because of previous claims that it reduces pain after surgery,” Mashour says. “We wanted to test this in a larger cohort along with the outcome of delirium in patients at high risk. 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.”
Avidan, lead author of the study, adds, “When patients become delirious after surgery, they tend to spend more time in the intensive care unit, have longer hospital stays and have a greater chance of dying. Overall, patients who develop delirium have worse outcomes and are at higher risk for long-term cognitive decline. It’s really important to try to prevent it if we can.”