Abstract: Objective To compare the effects of common carotid artery and femoral vein administration of propofol for electrocerebral silence(ES)on circulatory and respiratory function and the dosage of propofol required during ES in dogs.Methods Eight dogs were anesthetized by common carotid arterial and femoral vein administration of propofol for ES for 1 h.The time of consciousness loss and recovery,dose of propofol during ES,mean arterial pressure,heart rate,respiration rate,end-tidal carbon dioxide,SpO2,cerebral state index(CSI)and anal temperature were continuously monitored.Changes in the outcome variables were analyzed at 7 time points,namely the baseline,upon loss of consciousness,at 10 s,30 min and 1 h of CSI=0,and recovery of CSI and consciousness.Results Carotid artery propofol administration produced ES with only half of the dose for intravenous administration.Compared with the baseline values,the mean artery pressure and respiration rate remained unchanged or decreased transiently during ES with carotid artery propofol administration.In contrast,intravenous propofol administration resulted in systemic hypotension and severe respiratory depression.Conclusion Carotid artery propofol administration produces ES with a much smaller dose than intravenous propofol administration without causing systemic hypotension or respiratory depression.