Is hypotensive anaesthesia guided by invasive intraarterial monitoring required for orthognathic surgery? - A retrospective review of anaesthetic practice and intraoperative blood loss in orthognathic surgery in a tertiary hospital

Background and Aims: Orthognathic surgeries for maxillofacial deformities are commonly performed globally and are associated with significant blood loss. This can distort the surgical field and necessitate blood transfusion with its concomitant risks. We aimed to review if invasive intraarterial (IA) line monitoring and/or hypotensive anaesthesia is required for orthognathic surgeries, and their effects on intraoperative blood loss and transfusion requirements. Methods: This was a retrospective observational study conducted in patients admitted for orthognathic surgeries in a public tertiary hospital. Anaesthetic techniques and intraoperative haemodynamics were studied for their effects on intraoperative blood loss. Results: The data from 269 patients who underwent orthognathic-bimaxillary surgeries was analysed. Inhalational anaesthetic combined with remifentanil was administered for 86.6%, total intravenous anesthesia to 11.2% patients, while the rest received inhalational anaesthesia. Hypotensive anaesthesia was achieved in 48 subjects (17.8%) and associated with shorter duration of surgery (349 vs 378 min, P = 0.02) and a trend towards lower blood loss (874 mL vs 1000 mL, P = 0.058) but higher transfusion requirement (81.3% vs 58.8%, P = 0.004). An IA line was used in 119 patients (44.2%) and was not associated with a higher probability of achieving hypotensive anaesthesia (19.3% vs 16.7%, P = 0.06). However, less blood loss (911 vs 1029 mL, P = 0.05) occurred compared to noninvasive blood pressure monitoring. Conclusion: Invasive blood pressure monitoring is as effective as noninvasive methods to achieve hypotensive anaesthesia. It does not aid in achieving lower target blood pressure. There is a lack of association between a reduction in blood loss and higher blood transfusion during hypotensive anaesthesia and this will require further evaluation.