1. Departments of Cardiology, Sapporo Shuyukai Hospital, Sapporo, Hokkaido, Japan
2. Departments of Neurosurgery, Sapporo Shuyukai Hospital, Sapporo, Hokkaido, Japan
3. Departments of Anesthesiology, Sapporo Shuyukai Hospital, Sapporo, Hokkaido, Japan