Patients who suffer longer bouts of delirium during lengthy stays in an intensive care unit stand a higher chance of developing mental deficits similar to those seen with a brain injury or early Alzheimer's disease, new research says.
Two of every five critical care patients developed thinking and memory difficulties like those in people with traumatic brain injuries after just three months' stay, while one in four had mental impairments similar to those seen in people with mild Alzheimer's.
"Even though our survival after critical illness has improved, a significant number of patients will suffer cognitive [mental] impairment after spending a long period in an ICU," said study author Dr Pratik Pandharipande, a professor of anaesthesiology and surgery at Vanderbilt University Medical Centre in Nashville.
Delirium appeared to play the main role in this mental impairment, the researchers found. The more time an ICU patient spent in a state of delirium, the more likely that patient was to suffer thinking or memory problems.
"That provides us with the potential to reduce the duration of delirium we see in ICU patients," Pandharipande said. "That may impact the cognitive impairment we see after critical illness."
The study, which is published in the New England Journal of Medicine, involved 821 ICU patients. Researchers monitored their progress and tested their ability to plan and solve problems at regular intervals.
At three months, 40% of patients displayed scores similar to patients with moderate traumatic brain injury and 26% had scores similar to those for patients with mild Alzheimer's.
These mental deficits persisted. A year later, about 34% of patients had scores similar to people with brain injuries and 24% had scores similar to those with mild Alzheimer's, the investigators found.
There didn't seem to be any particular type of patient more likely to suffer from impairment, Pandharipande said. The researchers found no significant differences based on gender, age or pre-existing health problems. Medical and surgical ICU patients both showed the same amount of risk.
"There was not a particular patient population that got separated out," he said. "All populations had the same risk of having cognitive impairment."
A long period of delirium was the only common denominator among those suffering impairment, the researchers noted.
"We think it's a brain organ dysfunction," Pandharipande said. "Delirium has been associated with cerebral atrophy, inflammation and changes in the brain's white matter. All these potentially could be the connection between delirium and long-term cognitive impairment."
While the study found an association between long periods of delirium and later mental impairment, it did not prove a cause-and-effect link.
Critical care physicians have been wrangling with this problem for decades, said Nancy Foster, vice president for quality and patient safety policy at the American Hospital Association, in Washington, DC.
"This is a helpful look at an issue that has long puzzled clinicians and hospital leaders what leads to some patients having continuing cognitive problems after being released from an ICU," Foster said. "It's really helping identify where further focus should be placed while we unravel the mystery here."
Pandharipande said critical care physicians should consider taking steps to limit the amount of time patients spend in a delirious state. Moderating the use of sedatives, working to keep patients awake and active, and getting them mobile as soon as possible all could help stave off the potential damage of delirium.
Physicians also might consider how to best prepare a person mentally, as well as physically, to leave the hospital.
"Perhaps at the back end of ICU we should start doing a cognitive rehabilitation at the same time we provide physical rehabilitation," he said.
For more on delirium, visit the U.S. National Library of Medicine.
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