Researchers have quantified the frequency of cognitive deterioration in former hospital ICU patients, and say it "may be a growing public health problem."
Hospital intensivists see it all the time. But they can't explain why months after discharge from critical care units, so many patients lose their ability to think, plan, or make decisions like they did before their admission.
This mysterious, often rapid downward spiral of their mental function increases the chance they will fall, be readmitted, require expensive nursing home care, or other assistance, or have some other poor outcome if they try to live on their own.
Now researchers have not only quantified the frequency of this deterioration, which they say "may be a growing public health problem" because of the number affected. But they also have identified a culprit.
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Three months after discharge, four in 10 patients had cognition scores worse than those in people with moderate traumatic brain injury, and one year after discharge, explains Pratik Pandharipande, MD, lead author and critical care specialist at Vanderbilt University Medical Center.
The paper is published in Thursday's New England Journal of Medicine. Both medical and surgical intensive care unit patients were studied.
After one year, "51% of survivors had cognitive impairments 1.5 standard deviations below their age and education-level adjusted mean scores," he says.
Additionally, he says, "one in four patients had scores very similar to what would be seen in patients with Alzheimer's disease."
The researchers then looked at what factors provoked the loss of mental function in these patients. They found that the longer a patient endured an episode of delirium in the ICU, measured by altered levels of consciousness, inattention, and disorganized thinking—a relatively common occurrence during extended hospitalization—the more likely the patient was to have a significant decline in ability to think, a correlation noted up to a year after patients were discharged.
"The cause of their loss of cognitive function was definitely not what brought them into the ICU," Pandharipande, says.
That may be good news in a way, Pandharipande says, "because there are many ways we think we can reduce delirium," as some hospital protocols are beginning to show.
For example, when patients need sedation, light sedatives can be used instead of heavier drugs like benzodiazepines. Patients can be prompted to be kept awake, alert, and interactive. And when they are supposed to go to sleep, they can be left alone to sleep instead of being awakened repeatedly for tests or to be checked on.
"If there are times during hospitalization when patients are not as critically ill, we can consider letting them sleep, turn[ing] off monitors beeping in their bedrooms, and not [giving] patients baths at 2 a.m. just because it's convenient for the healthcare team," Pandharipande says.
So often when patients are critically ill, he says, hospital teams say "'let's keep them sedated and not wake them up and interact with them, or let them interact with the environment,'" he says.
"After an illness, the lung, heart and kidneys tend to recover, but the brain probably has the least reserve, and illness may have longer lasting implications," he says, adding "perhaps we need to exercise the brain as well."
The researchers also found an association between a loss of a patient's ability to make decisions at three months, but not at the study's end point of 12 months. Also, use of other drugs like propofol, dexmedetomidine, and opiates did not appear to impact cognitive function.
The clinical trial, which was funded by the National Institutes of Health and others, enrolled 821 patients who had been admitted to either Vanderbilt or Saint Thomas Hospital in Nashville ICUs, and were followed for one year through May of 2010. All the patients were hospitalized for treatment of respiratory failure or shock.
Pandharipande says it's important that physicians who treat patients after their discharge "recognize that this is an entity that does exist, so when patients come to us saying they are having problems with memory or executive function (the ability to organize and make decisions), that they can't plan things or manage their finances, we don't blow them off and say, 'don't worry, you'll get better.' Because we don't know they're going to get better."
He adds that too often providers consider themselves "successful if we get our patients out of our hospitals alive. But perhaps we need to think harder about getting them back to the quality of life they had prior to their hospitalization. That would be a better barometer of success."
Hinging on earlier work by his team, Pandharipande also is looking for how the neurochemical process that causes delirium may be damaging regions of the brain affecting cognition. That work is still in progress, he says.
In an accompanying editorial, Margaret Herridge, MD and Jill Cameron, of the Division of Critical Care and Division of Pulmonary and Critical Care at the University Health Network in Toronto, say the Vanderbilt study "unequivocally" shows that neurocognitive dysfunction is a common event after critical illness.
And, they wrote, the researchers "underscore that surveillance and intervention for delirium remain crucial to best ICU practice, as does an ICU culture of wakefulness and mobility."
The study "should fuel an informed discussion about what it means for our patients to survive an episode of critical illness, how it changes families forever, and when the degree of suffering and futility becomes unacceptable from a patient-centered and societal standpoint," they wrote.