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

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Abstract

The effects of stimulation of the sciatic nerve for 5 min on the cerebral metabolic rate for oxygen (CMRO2), cerebral blood flow (CBF) and EEG were investigated in anesthetized dogs. With halothane, 0.5 and 0.9 per cent, CMRO2 maximally increased by 19 and 20 per cent at 1 min with EEG activation, and CBF by 17 and 43 per cent, respectively. With halothane, 1.4 per cent, CMRO2 and EEG remained unchanged, but mean CBF increased by 30 per cent for 5 min. With methoxyflurane, 0.12 and 0.25 per cent, CMRO2 increased by 16 and 15 per cent at 1 min with EEG activation, and CBF by 23 and 26 per cent, respectively. With methoxyflurane, 0.38 percent, CMRO2 and EEG remained unchanged, but mean CBF increased by 9 per cent for 5 min. With morphine, 0.5 and 1.5 mg/kg, CMRO2 increased by 15 and 17 per cent at 1 min with EEG activation, and CBF by 25 and 21 per cent, respectively. With morphine, 1.5 mg/kg, plus nitrous oxide, 60 per cent, CMRO2 and CBF increased by 19 and 39 per cent at 1 min with EEG activation, and mean CBF by 24 per cent 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. These results suggest that the coupling of CMRO2 and EEG was maintained in all anesthetic circumstances, but the coupling of CMRO2 and CBF varied with individual anesthetic doses.

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