A brain function monitor for use during anaesthesia. Preliminary report.

This simple on-line monitor provides simultaneous noninvasive quantification of continuous processes within the brain, by measuring the augmented delta quotient (ADQ; the proportion of low frequency components in the electroencephalogram). The response of the ADQ, both during experiments in animals and in children undergoing surgery, during cardiopulmonary bypass with and without hypothermia, demonstrates that this concept may prove valuable both to monitor anaesthetic depth and to warn of impending cerebral impairment.