Electroconvulsive therapy (ECT) is an effective treatment for severe depression and other psychiatric disorders. ECT is usually given in several sessions on different days. During each session, patients receive short-acting anesthesia to ensure comfort and safety.

This study aims to evaluate whether the amount of anesthetic medication required changes during repeated ECT sessions in the same patient. In addition, the study will examine the relationship between anesthetic dose, seizure duration, seizure quality (measured by postictal suppression index), and recovery time.

This is a prospective observational study. All anesthesia and ECT procedures will be performed according to routine clinical practice. No additional intervention will be applied for research purposes.

Electroconvulsive therapy (ECT) is a well-established biological treatment for treatment-resistant depression and other affective disorders. Adequate anesthesia is essential to ensure patient safety while maintaining optimal seizure quality and therapeutic efficacy. Short-acting anesthetic agents are commonly used in ECT due to their favorable recovery profiles and hemodynamic stability.

Previous studies suggest that anesthetic requirements may change across repeated ECT sessions, potentially influencing seizure duration, seizure quality, and recovery time. However, evidence regarding within-patient changes in anesthetic dose requirements and their relationship with electroencephalographic seizure characteristics remains limited.

This prospective observational cohort study aims to evaluate changes in anesthetic requirements during repeated ECT sessions in adult patients. Secondary objectives include examining the association between anesthetic dose, seizure duration (motor and EEG), postictal suppression index (PSI), and recovery time.

All ECT and anesthesia procedures will be conducted according to institutional routine clinical protocols. The research team will not interfere with clinical decision-making. Data will be collected from anesthesia records and EEG documentation. Mixed-effects statistical models will be used to account for repeated within-subject measurements.

Inclusion Criteria:

• Age 18 to 65 years.
• Scheduled to undergo electroconvulsive therapy (ECT) under elective conditions as part of routine clinical care.
• ECT indication (e.g., major depressive disorder, bipolar depression, schizoaffective disorder, catatonia).
• ASA Physical Status I-III.
• Planned to receive multiple ECT sessions.
• Able to provide written informed consent (participant and/or legally authorized representative).

Exclusion Criteria:

• Use of antiepileptic drugs or benzodiazepines that may affect seizure threshold.
• ECT received within the past 6 months.
• Severe cardiovascular, pulmonary, or neurologic comorbidity (investigator judgment).
• Pregnancy or breastfeeding.
• ASA Physical Status IV or higher.
• Acute substance or alcohol use disorder/intoxication.
• Conditions preventing EEG monitoring (e.g., scalp trauma, significant skin lesions, cranial implants).
• Inability to obtain reliable BIS monitoring during anesthesia induction due to technical limitations.

Adult patients aged 18-65 years with an established indication for electroconvulsive therapy (ECT) who are scheduled to undergo multiple ECT sessions at a tertiary care hospital. Participants will be consecutively enrolled during the study period according to eligibility criteria. All procedures will be performed as part of routine clinical care.