Ⅰ.IntroductionOrthognathic surgery(OGS)is widely recognized as a form of orthodontic treatment and was previously performed chiefly on the mandible, but in the quest for better outcomes, an increasing number of orthognathic surgeries are now being performed on the upper or lower jaw 1) . With improvements in surgical technique, ready availability of autologous blood, and the introduction of hypotensive anesthesia, surgery can be performed without recourse to allogeneic blood transfusions 1) . To date, a nationwide survey 1,2) by the Japanese Society for Jaw Deformity Research and clinical statistics 3 5) from various institutions have been published, but there are few studies of differences in blood loss due to anesthetic management methods. Therefore, the present, retrospective, observational study examined anesthesia management method as an explanatory variable, analyzed intraoperative blood loss as an outcome, and examined factors independently affecting the amount of intraoperative blood loss. This study was approved by the Ethics Review Board of the study center(No. 5 12)and adheres to the tenets of the Helsinki Declaration and STROBE guideline.
Ⅱ.Objects and Methods
Intotal, 157 patients who underwent a Le Fort I osteotomy (LFI) plus sagittal splitting ramus osteotomy (SSRO)or SSRO alone between April 2010 and March 2023 at Tokyo Metropolitan Tama Medical Center were included. Intraoperative blood loss in the anesthesia records of patients was used as the objective variable. The explanatory variables, including basic patient information(age, sex, height, weight, and BMI) , anes-