Abstract: Objective: To compare the blood loss under the reverse Trendelenburg 10° position and the horizontal position in patients with bimaxillary orthognathic surgeries. Methods: Sixty-three patients were enrolled in the prospective, randomized clinical study. Thirty-two subjects accepted the surgeries under the reverse Trendelenburg 10° position and 31 subjects under the horizontal position. The intraoperative blood loss and the bleeding per minute during Le Fort I osteotomy, bilateral sagittal ramus osteotomy and horizontal genioplasty were estimated.Results: The total blood loss of the surgeries under the reverse Trendelenburg 10° position (147.1±62.6) mL was significantly lower than that of the surgeries under the horizontal position (243.9±86.8) mL (P<0.001). The bleeding per minute of the surgeries under the reverse Trendelenburg 10° position (0.78±0.25) mL/min was also significantly lower than that of the surgeries under the horizontal position (1.20±0.39) mL/min (P<0.001). The surgeons had significant influence on the total blood loss (P<0.001) but no significant influence on the bleeding per minute (P=0.78). Conclusion: Compared to the horizontal position, the reverse Trendelenburg position 100 can significantly reduce the blood loss in bimaxillary orthognathic surgery. The shorter operative time was, the smaller amount of the total blood loss was.

Key words: Operative position, Blood loss, Orthognathic surgery