A 24-year-old female complains of suicidal ideation. She lost her family in a car accident earlier this year. Since then, she had problems with focusing on her work. She was laid off from her work as she was making many errors due to false judgment. She was rescued from suicidal attempts a couple of times. She was prescribed electroconvulsive therapy. The intravenous anesthetic of choice for electroconvulsive therapy is: