Cardiopulmonary Bypass Confirmed as a Risk Factor for Impaired Cognitive Function

The use of cardiopulmonary bypass (CPB) is indeed the cause of cognitive impairment associated with coronary artery bypass grafting (CABG), according to a report in the December 2001 The Annals of Thoracic Surgery.

Cognitive brain dysfunction follows CABG in 20% to 80% of patients, the authors explain, but the causes “have long been a topic of debate.”

Dr. Michael Grimm and colleagues, from Vienna General Hospital, Austria, used P300 auditory-evoked potentials–a highly sensitive and reproducible tool for assessing cognitive function–to determine the predictors of cognitive brain dysfunction in 308 survivors of CABG.

CABG significantly prolonged the cognitive P300 peak latency, an indication of impairment, at 7 days, the authors report, and peak latencies nearly normalized by 4 months after surgery.

The Mini Mental State Examination and the Trail Making Test, however, failed to detect any significant changes throughout the study period, the report indicates.

Univariate analysis seemed to link the number of grafts, the number of diseased vessels, and the use of CPB with impaired cognitive function at 7 days, the researchers note. By the 4-month followup assessment, only the use of CPB and the number of diseased vessels were associated with cognitive dysfunction.

Multivariate analysis, however, identified the use of CPB as the only independent predictor of cognitive impairment 7 days or 4 months after CABG, the investigators say, and patients who underwent CABG without CPB showed improvements in P300 peak latencies.

“This study shows [for the first time] that the use of CPB is the only independent predictor of cognitive decline after CABG at 7-day and 4-month followup,” the authors conclude.

Ann Thorac Surg 2001;72:1926-1932.