CHANGE IN CEREBRAL BLOOD-FLOW VELOCITY WITH ONSET OF EEG SILENCE DURING INHALATION ANESTHESIA IN HUMANS - EVIDENCE OF FLOW METABOLISM COUPLING

In eight subjects anesthetized with moderate to high doses of inhalati on anesthetics (isoflurane or desflurane) during normocapnia, the onse t of electrical silence in EEG was associated with a sudden reduction of brood flow velocity monitored from the middle cerebral artery. The magnitude of this reduction was 38 +/- 11% (mean +/- SD; range 24-44%) . The change in EEG always preceded the change in flow velocity by 5-7 s. These observations suggest that some flow-metabolism coupling mech anism is preserved during inhalation anesthesia in humans.