MODIFICATION OF THE RELATIONSHIP BETWEEN CEREBRAL METABOLISM, BLOOD-FLOW, AND ELECTROENCEPHALOGRAM BY STIMULATION DURING ANESTHESIA IN THE DOG

The effects of stimulation of the sciatic nerve for 5 min on the cerebral metabolic rate for oxygen (CMR(O2)), cerebral blood flow (CBF) and EEG were investigated in anesthetized dogs. With halothane, 0.5 and 0.9 per cent, CMR(O2) 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, CMR(O2) and EEG remained unchanged, but mean CBF increased by 30 per cent for 5 min. With methoxyflurane, 0.12 and 0.25 per cent, CMR(O2) 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 per cent, CMR(O2) and EEG remained unchanged, but mean CBF increased by 9 per cent for 5 min. With morphine, 0.5 and 1.5 mg/kg, CMR(O2) 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, CMR(O2) and CBF increased by 19 and 39 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 CMR(O2). These results suggest that the coupling of CMR(O2), and EEG was maintained in all anesthetic circumstances, but the coupling of CMR(O2) and CBF varied with individual anesthetic doses.