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 before and after open-heart surgery under cardiopulmonary bypass: postoperatively, 19 patients (30%) showed no clinical neuropsychiatric symptoms, whereas in 35 patients (56%) mild or transient neurological signs and in nine (14%) severe neurological complications were found. The postoperative EEG changes were characterized by a slight delta-theta increase, an alpha decrease and a significant slowing of the dominant frequency from 9.7 to 9.3 Hz. In brainstem auditory evoked potentials no changes were found, and in somatosensory evoked potentials (median nerve) the latency of the early cortical component, N20, increased. Cardiovascular reflexes showed increased changes, similar to those found in autonomic neuropathies. In the neuropsychological test battery, the Visual retention test (Benton) and the Rorschach test showed slight postoperative improvement, whereas other psychometric variables (flicker fusion frequency, reaction time) did not change. Despite an improved operative technique some minor clinical and neurophysiological disturbances of the central nervous system remain. However, specific pre- or peri-operative risk factors for these postoperative disturbances or complications could not be identified.