Modification of the Relationship between Cerebral Metabolism, Blood Flow, and Electroencephalogram by Stimulation during Anesthesia in the Dog

Abstract

The effects of stimulation of the sciatic nerve for 5 min on the cerebral metabolic rate for O2 (CMRO2), cerebral blood flow (CBF) and EEG were studied in anesthetized dogs. With halothane, 0.5 and 0.9%, CMRO2 maximally increased by 19 and 20% at 1 min with EEG activation, and CBF by 17 and 43%, respectively. With halothane, 1.4%, CMRO2 and EEG remained unchanged, but mean CBF increased by 30% for 5 min. With methoxyflurane, 0.12 and 0.25%, CMRO2 increased by 16 and 15% at 1 min with EEG activation, and CBF by 23 and 26%, respectively. With methoxyflurane, 0.38%, CMRO2 and EEG remained unchanged, but mean CBF increased by 9% for 5 min. With morphine, 0.5 and 1.5 mg/kg, CMRO2 increased by 15 and 17% at 1 min with EEG activation and CBF by 25 and 21%, respectively. With morphine, 1.5 mg/kg, plus N2O, 60%, CMRO2 and CBF increased by 19 and 39% at 1 min with EEG activation, and mean CBF by 24% for 5 min. In all instances where EEG was activated it was attenuated with time during stimulation and was associated with a less-pronounced or insignificant increase in CMRO2. Apparently the coupling of CMRO2 and EEG was maintained in all anesthetic circumstances, but the coupling of CMRO2 and CBF varied with individual anesthetic doses.