Modification of Cerebral Metabolic and Circulatory Response to Nitrous Oxide by Diazepam， Morphine or Hypocapnia in Dogs

Modification of cerebral metabolic and circulatory response to nitrous axide by prior administration of diazepam, morphine or induction of hypocapnia was studied in 24 dogs. Nitrous oxide (60 per cent end-tidal) increased cerebral oxygen consumption by 20 per cent and increased cerebral blood flow by 150 per cent initially and then cerebral blood flow declined to 50 per cent adove the control during a 60-min period. Cerebrospinal fluid pressure significantly increased. Diazepam, 0.5 mg/kg, significantly attenuated cerebral metabolic and circulatory stimulation with nitrous oxide for 30 min. Morphine, 1 mg/kg, blocked the cerebral stimulationwith nitrous oxide throughot the period. Increase in cerebrospinal fluid presure was significantly attenuated by both drugs the early period. Indyced hypocapnia transiently but significantly attenuated the increases in cerebral blood flow and cerebrospinal fluid presure with nitrous oxide, while cerebral oxygen consumption was unaffected. These results indicated that cerebral metabolic and circulatory response to nitrous oxide is attenuated or blocked by diazepam, morphine or induced hypocapnia in dogs.

cerebral metabolism and circulation

nitrous oxide

diazepam

morphine

hypocapnia