Cognitive impairments persist

December 9, 2011 - 05:00

Many patients who have survived serious ailments or a cardiac arrest experience a lingering cognitive impairment.

A significant functional impairment of the brain was found in patients after being released from the hospital. (Photo: Colourbox)

This has been revealed by a study at Haukeland University Hospital in Bergen, Norway.

Cognitive impairment is a general term for a reduction in a number of mental functions we use daily. Among them are various types of memory, attention, concentration and planning. Even a mild reduction of these functions can have serious consequences.

“I excluded all the patients who already had a heightened risk of a reduced brain function. Then I carried out cognitive tests on patients who presumably would not be expected to have such an impairment,” says Johan Torgersen, who headed up the study. The study was part of his recent doctoral thesis.

Connection with disease

Torgersen conducted his research with two patient groups. One consisted of patients who had been treated following a cardiac arrest; the other was made up of patients who were admitted to intensive care units for a variety of serious illnesses.

In the latter group 64 percent had cognitive impairments right after being released. 

These were patients who had been admitted to the intensive care ward for treatment of chronic obstructive pulmonary disease, blood poisoning, serious haemorrhaging or other critical maladies.

These patients had no brain damage or head trauma, yet a significant functional impairment of the brain was evident.

“This leads us to think that the cognitive functional debilitation must have had something to do with their illness,” says Torgersen.

One year later

Most of the patients in this group improved quickly, and after three months about 90 percent of them had normal cognitive function.

But a second check-up nine months later revealed that 10 percent still had cognitive problems. This was a year after being released from hospital and the patients’ problems can thus be considered permanent.

The collected data from the cardiac arrest group is even less positive. About half of them had cognitive problems one or two years after their hearts had stopped and been re-started.

Torgersen’s doctoral thesis asserts that the findings from these two patient groups indicate critical illness, no matter where in the body it strikes, can lead to cognitive problems. He tells that this opens for several possible explanations.

Johan Torgersen is a specialist in anaesthesiology. (Photo: StudioVest)

“We don’t know concretely what happens, but it’s clear that a reduction of oxygen supply to the brain cells is relevant. This can occur in various ways. The flow of blood to the brain can be reduced or the oxygen supply to the blood can be insufficient.

“It’s likely that being critically ill can cause changes on the cellular level and a difference in the arterial walls can alter the way oxygen and certain substance transfer from the blood to the cells.”

Torgersen explains that cognitive impairment can also stem from mental disorders.

“Lots of patients develop anxiety, depression or post-traumatic stress due to serious illness,” he points out.

“Another explanation could be that a person who is critically ill simply does less thinking. This absence of cognitive activity might also lead to impairment.”

Tested with computer games

Patients’ cognitive functionality was subjected to the Cambridge Neuropsychological Test Automated Battery, a tool for cognitive testing developed at Cambridge University.

The tests appear as easy computer games designed to test functions like memory, attention and reaction skills.

Torgersen had each patient complete four problems from this test during a 45-minute period, and compared their test results with the average for a general population. This would reveal any deviations from the norm.

Thorough testing was required because cognitive impairments for many patients were subtle and sometimes hard to notice.

“We need to keep in mind that some patients have a reduced cognitive level even though it isn’t immediate apparent. I think tests of brain functions should be made routine during treatment and when following up critically ill patients,” says Torgersen.

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Read the article in Norwegian at forskning.no

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Translated by
Glenn Ostling

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