Depression is a common clinical mental disease with high incidence rate, high recurrence rate, high suicide rate and high disability rate. As a first-line treatment for depression with refractory, high suicide risk and obvious psychotic symptoms, electric shock has a definite effect on depression, but may lead to cognitive impairment. The induction of extensive epileptiform discharges in the cerebral cortex by electric shock therapy is the key to ensure the treatment effect. The level of epileptiform discharges in the brain is mainly reflected in the quality of convulsions. The quality of electroconvulsive convulsions is affected by factors such as age, stimulation power, anesthetic drugs and depth of anesthesia. Most anesthetics have anticonvulsive properties, such as barbiturate or propofol, which may have a negative impact on the quality of convulsions, thus affecting the therapeutic effect. If the parameters of electric shock, such as stimulation dose, are modified, although the quality and treatment effect of convulsions can be improved, it may also lead to higher cognitive side effects. The depth of anesthesia also affects the quality and efficacy of electric shock convulsions, and the quality of convulsions is higher when stimulated at a shallow level of anesthesia. However, if the use of narcotic drugs is reduced to improve the quality of convulsions, the risk of restlessness and delirium after electric shock may be higher and the comfort of patients may be lower. Therefore, this study compared the effects of different anesthesia induction schemes on the quality and clinical efficacy of electroconvulsive seizures in patients with depression based on EEG monitoring, and explored the optimal depth of anesthesia.

This study is a randomized controlled, single blind clinical trial comparing the quality of convulsions and clinical effects of electroconvulsive therapy under different levels of consciousness index (IoC).A total of 24 participants were included in this study, all from the inpatient department of the Psychiatric Department of the First Affiliated Hospital of Chongqing Medical University. They were diagnosed as depression patients according to the International Classification of Diseases (ICD-11), and their depression level and cognitive function level were evaluated by trained psychiatrists; In the study, the subjects use the EEG bispectral index monitor (Apollo-9000A) to monitor IoC1(Index of consciousness 1) and IoC2(Index of consciousness 2) before electric shock.Then anesthesia induction was performed using propofol 1.5mg/kg and scoline 1mg/kg. According to the difference in consciousness index 1 (IoC1), the subjects were randomly divided into three groups, namely H group (IoC1 60-70), M group (IoC1 50-60), and L group (IoC1 40-50). All subjects underwent assisted breathing after anesthesia induction, monitoring the concentration of end-expiratory carbon dioxide, and conducting electrical stimulation when the consciousness index reached the corresponding level,and the electrode position is bilateral temporal area. The main outcome measure is EEG seizure duration ,and the secondary outcome measures include average Seizure Energy Index(SEI), electric shock stimulation energy, post-seizure inhibition index, the fastest heart rate, Hamilton Depression Scale (HAMD-24) score, Montreal Cognitive Assessment Scale (MoCA) score, adverse reactions during awakening and the interval between anesthesia induction and the start of electrical stimulation.

Due to the varying frequency of electroconvulsive therapy performed by each subject, with an average of 6-12 times and varying duration of each electroconvulsive treatment, this study uses a mixed effects model to analyze the relationship between different consciousness indices and patient factors on the duration of EEG seizures. The depression score and cognitive function score before and after the complete course of electric shock are compared between groups using LSD-t test.

Inclusion Criteria:

• In-patients who meet the diagnostic criteria of moderate and severe depression in the 11th edition of the International Classification of Diseases (ICD-11)
• Age 18-60 years old, gender unlimited
• Primary school or above education level
• Indications for MECT treatment
• Normal hearing and vision (including color discrimination)
• The patient voluntarily participated in the study and signed the informed consent form, and the guardian also signed the informed consent form.

Exclusion Criteria:

• History of physical disease, brain organic disease and abuse of alcohol and psychoactive substances
• Patients with bipolar disorder
• Primary insomnia
• Combined with other mental diseases
• Combined with obesity, diabetes and other metabolic diseases
• Combined with hypertension, cardiovascular disease or cerebrovascular disease
• Combined with Alzheimer's disease
• Pregnant and lactating women.

Due to the fact that anesthesiologists need to determine the timing of electrical stimulation based on the level of consciousness index during the treatment of electric shock, this study is a randomized controlled, single blind study. The subjects were not aware of their grouping, consciousness index level, and the anesthesiologist was aware of the subjects' consciousness index level, but did not participate in data analysis. The data analyst is not clear about the specific content of the grouping.