ABSTRACT
The effects of lorazepam on cerebral function, metabolism, and hemodynamics were studied in eight dogs receiving a general anesthesia with isoflurane(0.5 vo1%)-50% nitrous oxide-oxy-gen. The effects of benzodiazepine antaronist, flumazenil, were also examined. Lorazepam(0.5 mg/kg) administration did decrease mean arterial pressure(MAP) and herat rate(HR). It did significantly decrease cerebral blood flow(CBF)(measured by posterior sagittal sinus outflow method) by 25% of control value(68+/-l3 vs. 51+/-12ml/100gm/min, meanSD) and cereberal metabolic rate for oxygen(CMRO ) by 17% (3.96+/-1.04 vs. 3.30+/-0.92ml/l00gm/min, mean+/-SD). Electroencephalogram(EEG) converted to high amplitude, predominantly theta and delta activity. Intracranial pressure(ICP) increased markedly. Following flumazenil(0.06 mg/kg) administration, HR recovered completely to control level but MAP increased only at 5 min. compared to pre-flumazenil value and returned to pre-flumazenil level. CBF recovered to control level for 15 min. and deereased after 30 min. compared to control level but higher than pre-flumazenil level about 9-15%. CMRO recovered completely to control leveL EEG changed to an awake pattern after fluamzenil administration. It is concluded that lorarepam decreased cerebral function and metabolism and depressed hemodynamic fuction. Benzodiazepine antag- onist, flumazenil, was effective in reversing cerebral and hemodynamic effects, may be in dose related manner.