Hemodynamic Changes and Trigeminocardiac Reflex During Bimaxillary Orthognathic Surgery

This study will use a prospective observational cohort design. Patients undergoing bimaxillary orthognathic surgery at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Kırıkkale University, will be included. Intraoperative hemodynamic data routinely collected as part of standard clinical monitoring will be recorded and analyzed. Hemodynamic parameters, including systolic blood pressure, diastolic blood pressure, heart rate, and peripheral oxygen saturation, will be recorded at 5-minute intervals throughout the surgical procedure.Hemodynamic parameters will be evaluated according to the different stages of surgery. The maxillary surgical stages will include anesthesia induction, incision, bone cutting, pterygoid intraoral incision, right and left lateral wall osteotomies, medial and lateral nasal wall osteotomies, maxillary down-fracture, maxillary mobilization, plate fixation, and suturing. The mandibular surgical stages will include anesthesia induction, incision, lingula incision, external oblique incision, osteotomy, mandibular separation, mandibular mobilization, plate fixation, and suturing.The occurrence of trigeminocardiac reflex (TCR) will be assessed simultaneously with the hemodynamic parameters recorded at each surgical stage. TCR will be classified as mild when heart rate and/or blood pressure decreases by 10-20% from baseline values and as severe when the decrease exceeds 20% and/or is accompanied by cardiac rhythm disturbances. Patients with and without TCR will be compared with respect to demographic characteristics and intraoperative hemodynamic changes observed during different surgical stages. No additional interventions, laboratory tests, or invasive procedures will be performed beyond routine clinical care. The findings of this study are expected to improve the understanding of intraoperative hemodynamic responses and contribute to the early recognition and management of TCR during bimaxillary orthognathic surgery.