Effect of blood pressure elevation on cerebral oxygen desaturation in the beach chair position

Objective: The beach chair position (BCP) during shoulder arthroscopy is a known risk factor for cerebral ischemia. We retrospectively investigated whether maintaining the arterial blood pressure (ABP) prevented the decrease in the regional cerebral tissue oxygen saturation (rSO2). Methods: We analyzed 20 consecutive patients who underwent elective shoulder surgery in the BCP under general anesthesia. The bilateral rSO2 was monitored continuously throughout the procedure with the help of near-infrared spectroscopy (INVOS 5100 Cerebral Oximeter, Somanetics Corporation, Troy, MI, USA). Anesthesiologists maintained patient blood pressure while they were in the BCP, which was measured using an ABP transducer placed at the level of the external auditory meatus. We compared rSO2 measured in the supine position and in the BCP. Results: Measurement of cortex level mean ABP (mABP) values in the BCP were >50 mmHg and over 60% higher than those noted for the supine position in most patients. Although all bilateral rSO2 values in the BCP were significantly lower than those in the supine position, the reductions was 50 mmHg, a decrease was recorded in the rSO2 values. This rSO2 decrease was proportional to the reduction in the cortex level mABP induced by a postural change to the BCP. Therefore, despite appropriate blood pressure management, shoulder surgery in the BCP might involve certain risks for patients with cerebrovascular diseases.