Two-thirds of patients sick enough to land in a hospital intensive care unit come away from the experience with substantial mental deficits, a new study has found.
The new research, which quantifies a phenomenon long observed by critical-care physicians, found that three months after leaving the hospital, 4 in 10 patients continue to have cognitive problems on a par with those seen in cases of moderate traumatic brain injury. And more than a quarter experience a decline in mental function akin to that seen in patients with mild Alzheimer’s disease, the study says.
For 58% of patients who’ve experienced a stay in the ICU, those intellectual deficits are still there a year after they have been released from the hospital, the study found.
The latest research, published Wednesday in the New England Journal of Medicine, found that the sudden decline in mental function was as likely to affect young patients as it was those who were older. And it was no more likely in patients who were ill even before their hospitalization than it was in those who had been healthy.
In fact, only one factor appeared to predict which patients would sustain mental deficits after an ICU stay: the length of time the patient experienced delirium, a common occurrence among the hospitalized critically ill. The study tracked for a year 821 patients who landed in the ICU from a wide range of circumstances. Some were admitted following surgery; others came to intensive care after suffering a stroke, a sudden turn in an ongoing illness, or injury.
The authors of the study, physicians at Vanderbilt University Medical Center and Thomas Hospital in Nashville, were cautious in explaining why ICU patients so often emerge with substantial cognitive impairment. While suspicion has long fallen on the widespread use of powerful painkillers and sedatives in the ICU, they found few clear links between the medications a patient got in the ICU and his or her subsequent cognitive health.
At the same time, the study authors observed a weak relationship between post-ICU mental decline and the use of benzodiazepines--anti-anxiety and hypnotic medications including diazepam (marketed as Valium). While that link “should be interpreted cautiously,” the authors said, its weakness should not encourage physicians to minimize the use of such drugs where possible.
The researchers suggested that delirium itself may contribute to loss of mental function, given that it is also linked to inflammation and the death of brain cells, which may either start a downward slide in brain health, or serve as a signal of that process.