Cerebral oxygenation in the beach chair position: a randomized comparison of 30° and surgeon-selected low-angle positioning during shoulder surgery

Background: The beach chair position (BCP) is widely used for shoulder surgery but has been associated with rare yet devastating neurological complications, possibly related to cerebral hypoperfusion. This study compared cerebral perfusion in patients undergoing shoulder surgery in the conventional BCP versus a fixed 30° inclination. Methods: In this prospective, randomized comparison, adults undergoing elective shoulder surgery in BCP under combined regional and general anesthesia were allocated to a control group (CG; surgeon’s preferred angle) or study group (SG; fixed 30° angle). Regional cerebral oxygen saturation (rSO₂) was continuously monitored using near-infrared spectroscopy. Cerebral desaturation events (CDEs) were defined as a ≥20% reduction from baseline. Mean arterial pressure (MAP), rSO₂, CDEs and interventions were recorded. Results: Forty-five patients were included (CG: n=22, SG: n=23). The mean inclination angle in the CG was 38.7° (30°–55°). Baseline characteristics were comparable between groups. CDEs occurred in three patients (7%) overall: two patients (9%) in the CG and one patient (4%) in the SG (P=0.607). Absolute rSO₂ values <55% were observed in 38% of patients, with no significant between-group difference (P>0.99). Vasopressor intervention for MAP reduction was required in 69% of patients (72% vs 65%, P=0.57). All procedures were completed without the need for repositioning. No clinically evident neurological complications occurred. Conclusions: Shoulder surgery performed in BCP at lower inclination angles, including 30°, is feasible and associated with a low incidence of CDEs when guided by intraoperative cerebral oximetry. Routine use of lower inclination angles and cerebral oximetry may reduce the risk of ischemic neurological injury in American Society of Anaesthesiologists I–III patients undergoing shoulder surgery in BCP. Level of evidence: I.