Central nervous system function after cardiopulmonary bypass

In a prospective study, an elderly group of patients (n = 63,47 male, 16 female, age 40–65 years) was examined beforeand after open-heart surgery under cardiopulmonary bypass: postoperatively,19 patients (30%) showed no clinical neuropsychiatric symptoms,whereas in 35 patients (56%) mild or transient neurologicalsigns and in nine (14%) severe neurological complications werefound. The postoperative EEG changes were characterized by a slightdelta-theta increase, an alpha decrease and a significant cantslowing of the dominant frequency from 9.7 to 9.3 Hz. In brainstemauditory evoked potentials no changes were found, and in somatosensoryevoked potentials (median nerve) the latency of the early corticalcomponent, N20, increased. Cardiovascular reflexes showed increasedchanges, similar to those found in autonomic neuropathies. Inthe neuropsychological test battery, the Visual retention test(Benton) and the Rorschach test showed slight postoperativeimprovement, whereas other psychometric variables (flicker fusionfrequency, reaction time) did not change. Despite an improvedoperative technique some minor clinical and neurophysiologicaldisturbances of the central nervous system remain. However,specific pre- or peri-operative risk factors for these postoperativedisturbances or complications could not be identified.