P300-MAPPING - A NEUROPHYSIOLOGICAL TOOL TO QUANTIFY CEREBRAL-DYSFUNCTION AFTER CORONARY-ARTERY BYPASS-GRAFTING

Objective parameters are needed to quantify cerebral dysfunction follo wing cardiac surgery in outcome and comparative studies. In this inves tigation we assessed the value of the late auditory evoked potentials N100 and P300 to measure the neuropsychological deficit after coronary artery bypass grafting (CABG). N100, an exogenous potential is influe nced by the stimulus pattern (frequency, intensity and stimulus presen tation rate). P300, an endogenous potential, depends on the cognitive processing invoked by the stimulus. With approval of the Human Investi gation Committee and the patients' consents, 52 subjects undergoing el ective CABG were enrolled. Operation, extracorporal circulation, anest hesia and postoperative intensive care were standardized. Twenty-chann el recordings of N100 and P300 were obtained for off-line analysis. P3 00 was elicited using an oddball paradigm with rare target tones inter spersed among frequent non-target tones. Additionally, neuropsychologi cal tests (syndrome short test SKT and letter cancellation test) were carried out. Neurological examination and all tests were compared preo peratively and one week postoperatively. A significant deterioration i n cerebral function was documented by the SKT score (P = 0.04), an inc rease in P300 latency (P = 0.004) and an increase of mistake rate in c ounting the P300 target tone (P = 0.02). No differences between preope rative and postoperative testing were found for letter cancellation, P 300 amplitude and any N100 parameter. No correlation was found between the preoperative/postoperative changes in SKT score and P300 latency. P300 was proved to be an objective neurophysiological parameter that allows for the quantification of cerebral function after CABG.