Blood Pressure Drop During Bypass Might Impair Thinking

Reasons for the phenomenon aren't yet clear, researchers say

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THURSDAY, June 14, 2007 (HealthDay News) -- Patients who experience a blood pressure drop during bypass surgery may be at increased risk for a short-term dip in their cognitive abilities.

Researchers at the Johns Hopkins University School of Medicine in Baltimore studied 15 patients, aged 57 to 81, who were given cognitive tests before and then three to five days after they had coronary artery bypass graft (CABG) surgery.

All the patients had a decrease in mean arterial pressure (MAP) during surgery compared with their MAP before surgery. MAP provides doctors with an estimate of the blood pressure in various organs in the body.

The study found that patients whose MAP decreased by 27 millimeters of mercury or more had an average decrease of 1.4 points (out of a maximum of 30 points) on a standard cognitive test. Patients with a MAP decrease of less than 27 millimeters of mercury increased their scores by an average of one point.

Patients with a high MAP before their surgery were more likely to score lower on the cognitive test after their surgery.

The researchers also used MRI to examine the brains of 13 of the patients. They found that patients whose MAP decreased by more than 27 millimeters of mercury were 2.7 times more likely to show evidence of acute stroke.

The study was published online this week in the Archives of Neurology and is expected to be published in the August print issue.

The preliminary data from this small study suggests "that a substantial decrease in MAP from a patient's baseline may be a risk factor for short-term cognitive dysfunction," the study authors wrote. "This may be in part because of an increased risk for radiographic stroke."

Further studies are needed, the researchers said.

More information

The Alzheimer's Association has more about mild cognitive impairment.

SOURCE: JAMA/Archives journals, news release, June 11, 2007

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