1. Department of Anesthesiology, Hokkaido University Hospital, N14W5, Sapporo 060-8648, Japan
2. Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, N14W5, Sapporo 060-8648, Japan
3. Department of Biostatistics, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
4. Department of Orthopedic Surgery, Hokkaido University Hospital, N14W5, Sapporo 060-8648, Japan