Is Your Brain the Same after Hospitalization in the ICU?

Delirium can have long term effects on brain function

Posted Nov 04, 2014

It is not uncommon to hear patients complain about cognitive problems after being hospitalized in an intensive care unit (ICU). What is known about brain function following such hospitalizations? If there are changes in brain function, do these changes persist?

Clinical investigators from Vanderbilt University assessed the cognitive function of over 800 patients who had been hospitalized in an ICU for acute respiratory disease, cardiogenic shock (the heart has trouble pumping enough blood), or septic shock (overwhelming infection leading to low blood pressure). They reported their findings in the New England Journal of Medicine.

The patients were in the hospital for an average of 10 days. Most were on a respirator for several of those days, and about 60% were comatose for about 3 days.  While only about 5% had cognitive impairment at baseline, nearly 75% of these patients developed a delirium that lasted 3 to 4 days, on average, while in the hospital. A delirium is a condition in which a patient is awake but disoriented and confused. Delirious patients have memory problems and often experience hallucinations and/or delusions; some become agitated.

About 60% of these critically ill patients survived the hospitalization and were alive one year later. Not unexpectedly, those 65 and older had a higher death rate than those 50 to 64 years old and a much higher death rate than those younger than 50.

Did the patients exhibit cognitive consequences a year after hospitalization? About 25% of the survivors demonstrated substantial cognitive deficits both 3 months and 12 months after discharge. These deficits included problems with memory and attention. Age did not seem to affect these results as the same percentage of younger, previously healthy patients had substantial cognitive deficits 3 months and 12 months after discharge as did older patients (65 and older).

Were specific factors associated with these persistent cognitive deficits? Yes, the longer patients experienced a delirium the more likely they were to have memory and attentional deficits after discharge. Exactly why this relationship exists isn’t known. It is possible that something about a delirium sets the stage for more long-term brain changes. It is also possible that the delirium is not causative of longer term cognitive dysfunction, but that some other unidentified mechanism leads to both short term delirium and longer term cognitive deficits.

This study only followed patients for 12 months, and it remains unknown what happens years later. Does improvement occur? Or do the deficits remain and do they increase a person’s risk for developing age-related disorders like dementia that can lead to further cognitive impairment?  What role do the specific illnesses that led to the hospitalization play?

Little is known about treatments for acute delirium or these persistent cognitive changes.  Would cognitive rehabilitation after discharge help reverse the cognitive deficits? Would starting such rehabilitation shortly after discharge lead to greater improvement than waiting several months?

This important study should sensitize us to the fact that a significant number of patients who require treatment in an ICU for serious illnesses may be left with memory and attentional changes. 

This column was written by Eugene Rubin MD, PhD and Charles Zorumski MD.