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 inhalation anesthetics (isoflurane or desflurane) during normocapnia, the onset 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 mechanism is preserved during inhalation anesthesia in humans.