The parents of a 2-year-old boy who died a year ago after being sedated with the drug propofol are accusing the hospital staff of malpractice.

The boy, who underwent surgery at Tokyo Women's Medical University Hospital in Shinjuku Ward to remove a lymphangioma, died in February 2014 of acute circulatory failure three days after he was put in the intensive care unit and given propofol intravenously for about 70 hours.

The parents filed a written accusation Thursday saying the medical team inflicted bodily injury resulting in death, as there was no justifiable reason to use such a large amount of the drug in their child's treatment.