[Effect of neuroleptanalgesia on the visual evoked potential (VEP) in man]

Visual evoked potentials (VEP) were monitored intraoperatively in 35 urological patients during modified neuroleptanalgesia. Control measurements were made in 18 awake, premedicated patients prior to induction of anesthesia. The latencies of the negative peaks (designed n1, n2, n3) increased significantly (p = 0.001) during anesthesia: n1 from 50,6 ms to 57,1 ms, n2 from 80 ms to 89,4 ms, n3 from 124,5 ms to 139,6 ms, no significant change in amplitude was seen. Changing paCO2 in the range from 20 mmHg to 50 mmHg during controlled ventilation did not affect latencies and amplitudes of visual evoked potentials (n = 10 patients). These influences of neuroleptanalgesia must be considered when recording visual evoked potentials intraoperatively during neurosurgical procedures (aneurysm-, pituar gland surgery) for monitoring optic nerve function.