Catastrophic neurologic complications related with shoulder surgery in the beach chair position have been reported. We aimed to investigate the  effects of applying the thigh-high compression stocking on cerebral oxygen saturation trying to reduce cerebral desaturation events in adults undergoing surgeries in the beach chair position. 
Patients were assigned randomly to either the control group or thigh-high compression stocking group according to randomization. On arrival to the operating room, all patients were placed in the supine position and sensors for Near-infrared spectroscopy (NIRS) and BIS were placed. After the induction of general anesthesia, patients were changed to place in the beach-chair position tilting up to 40 and remained in that position throughout the operation. Induced hypotension was not used during surgical procedure. Mean non-invasive blood pressure at the forearm level, invasive arterial blood pressure at the middle ear level and regional cerebral tissue oxygen saturation (rSO2) were recorded at the following times: 5 minutes after the induction of anesthesia, 3 minutes and 5 minutes after the beach-chair position, 1 hour after the beach-chair position, and 5 minutes after the supine position at the end of surgery. A decrease in the rSO2 of 20% or greater from the preoperative baseline was defined as a cerebral desaturation events and if cerebral desaturation occurred, the time and duration were recorded. When cerebral desaturation occurred, we checked blood pressure, depth of anesthesia, fraction of inspired O2, end-tidal carbon dioxide tension, and hemoglobin. If it persisted, intravascular fluid or ephedrine 5 mg was administered.
Patient characteristics, including age, sex, height, weight, preoperative hemoglobin values and medical condition such as hypertension and diabetes were similar between two groups. There was no significant differences observes between groups in the type of surgery, the duration of beach chair position, crystalloid administration and blood loss.

The overall repeated-measures ANOVA revealed that there was no interaction effect between groups and statistically significant difference in cerebral rSO2 value between groups. The incidence of hypotension was41.2% in the control group and 7.1% in the CS group (P=0.038). There was no significant difference in the incidence of cerebral desaturation events between groups.
This study showed that overall patients showed a decrease of the value of blood pressure and rSO2 after the beach chair position. The thigh-high compression stocking reduced the incidence of hypotension but could not contribute to prevent cerebral desaturation events.

Effects of compression stocking on cerebral oxygen saturation in patients undergoing surgery in beach-chair position