Effects of Intraoperative Prone Versus Supine Positioning on Postoperative Delirium

Background: Postoperative delirium (POD) is a common complication in geriatric patients. This prospective cohort study evaluated a possible influence of intraoperative positioning on the occurrence of POD, as intraoperative prone positioning could affect cerebral perfusion. Methods: We included 760 patients of ≥60 years scheduled for elective surgery in prone or supine positions. The primary outcome was POD incidence on the first five days after surgery, assessed via 3D-Confusion Assessment Method (3-D CAM) or Confusion Assessment Method for Intensive Care Units (CAM-ICU). Preoperative assessments included the American Society of Anesthesiologists (ASA) and New York Heart Association (NYHA) classifications as well as short screenings for the cognitive (modified Montreal Cognitive Assessment (MoCA)) and self-care status of the patient. Secondary outcomes were length of hospital stay (LOS) and mortality rates. Results: Postoperative delirium rates were similar in prone and supine patients (7.6% vs. 5.5%; p = 0.31), and logistic regression analysis revealed no association of intraoperative prone positioning with POD (odds ratio 1.42 (95% CI 0.68-2.92; p = 0.342)). The overall incidence of POD was 6.1% and was associated with older age (81.5 (CI 76.2-84.8) vs. 72.0 (CI 67.0-79.0) years; p < 0.01), higher ASA and NHYA classifications, lower preoperative modified MoCA, reduced independence in self-care (p < 0.001, respectively), and longer incision-to-suture times (107.0 (CI 73.0-173.0) vs. 85.0 (CI 60.0-130.0) minutes; p < 0.01). Postoperative delirium resulted in longer LOS (14.5 (CI 9.0-27.0) vs. 7.0 (CI 4.0-9.0) days; p < 0.001), and increased mortality (13.0% vs. 1.7%; p < 0.001). Conclusions: Intraoperative prone positioning was not associated with POD in patients aged 60 years or older (OR 1.42; CI 0.68-2.92; p < 0.340), and LOS and mortality as secondary outcome parameters were also similar in patients after prone and supine surgery. Future studies assessing additional and possible confounding factors and intraoperative systemic and regional hemodynamics and oxygenation are needed to verify this result and to evaluate cerebral hypoperfusion as a possible mechanism of POD.