Effects of anesthetics on depression after modified electroconvulsive treatment

INTERVENTION: GroupA) Propofol is used in the former half of the period and ketamine is used in the latter half of the period, during ECT procedure. GroupB) Ketamine is used in the former half of the period and propofol is used in the latter half of the period, during ECT procedure. GroupA) Only propofol is used in the former half of the period and combination of ketamine and propofol is used in the latter half of the period, during ECT procedure. GroupB) Only ketamine is used in the former half of the period and combination of ketamine and propofol is used in the latter half of the period, during ECT procedure. CONDITION: severe depression PRIMARY OUTCOME: HAM‐D((Hamilton depression score) SECONDARY OUTCOME: Pupil diameter measurement; Hear rate viriability INCLUSION CRITERIA: severe depression