The Effect of S-ketamine for Patients Undergoing Electroconvulsive Therapy (ECT)

Inclusion Criteria: * American Society of Anesthesiologists (ASA) Physical Status I-II * diagnose depressive disorders with DSM-IV * Without cognitive impairment * Without ECT in past 6 months Exclusion Criteria: * had other comorbid psychiatric diagnoses, including schizophrenia, mania * organic heart diseases, severe hypertension and arrhythmia * severe hepatic and renal diseases * severe cerebrovascular disorder or malformation, intracranial mass lesions and seizure * glaucoma or high intraocular pressure and intra-ocular pathology * severe haematological disease, fracture and obesity, pregnancy * severe respiratory tract disease or difficult ventilation or incubation * had pre-existing neurological disease or cognitive impairment * allergy to anesthetics * drugs abuse or alcohol addiction * family history of malignant hyperthemia * refuse to participate in this trial, had taken part in other clinical trial and with less education and couldn't understand the content of questionnaire