EFFECTS OF THIOPENTAL, KETAMINE, DIAZEPAM, XYLAZINE, AND NITROUS-OXIDE ON EEG SPIKE ACTIVITY AND CONVULSIVE BEHAVIOR DURING ENFLURANE ANESTHESIA IN SPONTANEOUSLY BREATHING ATROPINIZED CATS - EFFECT AT SURGICALDEATH

The effects of thiopental, ketamine, diazepam, xylazine and nitrous ox ide, and combinations of thiopental-nitrous oxide and ketamine-nitrous oxide on electroencephalographic (EEG) spike activity and convulsive behaviors in atropinized cats at surgical depth of enflurane anesthesi a were assessed quantitatively for 60 minutes during spontaneous venti lation. Mean inspired enflurane concentrations (MIEC) were reduced 16% to 29% by pretreatment with thiopental, ketamine, diazepam, and xylaz ine, and were reduced 19% by 66% nitrous oxide. The MIEC of cats anest hetized with thiopental-nitrous oxide-enflurane and ketamine-nitrous o xide-enflurane were 35% to 38% lower than that with nitrous oxide-enfl urane. Pretreatment with thiopental, ketamine, diazepam, and xylazine did not reduce the EEG spike frequency during anesthesia but did marke dly reduce the spike amplitude. The addition of 66% nitrous oxide did not alter the spike frequency during anesthesia but tended to reduce t he spike amplitude. Combinations of thiopental-nitrous oxide and ketam ine-nitrous oxide almost abolished the spike activity. The addition of 66% nitrous oxide prevented convulsive responses elicited by photic a nd auditory stimulation during enflurane anesthesia. Treatment with th iopental, ketamine, diazepam and xylazine, and combinations of thiopen tal-nitrous oxide and ketamine-nitrous oxide, completely prevented con vulsive responses during enflurane anesthesia.