1. Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute, Severance Hospital, Yonsei University College of Medicine, Korea.
2. Department of Anesthesiology and Pain Medicine, Cheil General Hospital & Women's Healthcare Center, Kwandong University College of Medicine, Korea.
3. Department of Obstetric and Gynecology, CHA General Hospital, College of Medicine, Pochon CHA University, Korea.
4. Department of Emergency Medicine, Hanyang University College of Medicine, Seoul, Korea.