Influence of beach chair position on cerebral oxygen saturation: a comparison of INVOS and FORE-SIGHT cerebral oximeter.

Background:Although beach chair position (BCP) is frequently used for shoulder surgery, a potentially detrimental influence on cerebral oxygenation is discussed. Therefore, the present study investigated changes in regional cerebral oxygen saturation (rSO(2)/StO(2)) during BCP comparing 2 different devices for near-infrared spectroscopy measurement.Methods:Data were collected in 35 patients undergoing shoulder surgery in BCP and compared with a control group of 35 awake volunteers. The rSO(2)/StO(2) was assessed using INVOS and FORE-SIGHT monitors. Mean arterial blood pressure (MAP), peripheral oxygen saturation (SpO(2)), PeCO(2), FiO(2), end-tidal sevoflurane concentration, and rSO(2)/StO(2) were measured before positioning, during BCP, and in supine position after surgery.Results:A decrease in rSO(2)/StO(2) could be observed after BCP (INVOS: 76.1% supine vs. 66.7% BCP, P<0.001; FORE-SIGHT: 78.6% supine, 66.1% BCP, P<0.001), which was reversible in supine position. This decrease correlated with MAP during BCP, while in supine position no correlation was detected. In control group BCP did not influence rSO(2)/StO(2). Changes detected with INVOS or FORE-SIGHT cerebral oximeter did not differ.Conclusion:BCP is associated with a decrease in rSO(2)/StO(2) of 10% in anesthetized patients, which is reversible after repositioning. No changes occurred in supine position under general anesthesia as well as in awake subjects in BCP. This underlines the assumption that vasodilation by anesthetics in combination with BCP evoke a drop in rSO(2)/StO(2). A strict hemodynamic management may be necessary to prevent desaturation events. Despite different technology used by the devices, the results of INVOS and FORE-SIGHT cerebral oximeters are comparable.