Effects of Beach-Chair Position and Induced Hypotension on Cerebral Oxygen Saturation in Patients Undergoing Arthroscopic Shoulder Surgery

Abstract

We investigated the effects of the beach-chair position and induced hypotension on regional cerebral oxygen saturation (rSO(2)) in patients undergoing arthroscopic shoulder surgery by using near-infrared spectroscopy. Twenty-eight patients scheduled for arthroscopic shoulder surgery were enrolled prospectively. After induction of anesthesia, mechanical ventilation was controlled to maintain Paco(2) at 35 to 40 mm Hg. Anesthesia was maintained with sevoflurane and remifentanil. After radial artery cannulation, mean arterial pressure (MAP) was measured at the external auditory meatus level and maintained between 60 and 65 mm Hg. The rSO(2) was measured by use of near-infrared spectroscopy. MAP and rSO(2) were recorded at the following times: before induction (T(0)), immediately after induction (T(1) [baseline]), after beach-chair position (T(2)), immediately after induced hypotension (T(3)), 1 hour after induced hypotension (T(4)), and after supine position at the end of surgery (T(5)). Cerebral desaturation was defined as a reduction in rSO(2) to less than 80% of baseline value for 15 seconds or greater. A total of 27 patients were evaluated until the end of this study. The MAP at T(2) was significantly lower than that at T(1). The MAP values at T(3) and T(4) were significantly lower than those at T(1) and T(2). The rSO(2) at T(2) was significantly lower than that at T(1). Unlike the pattern of change in the MAP, there was no additional decrease in rSO(2) at T(3) and T(4). There were 2 patients who had an episode of cerebral desaturation. The beach-chair position combined with induced hypotension significantly decreases rSO(2) in patients undergoing shoulder arthroscopic surgery under general anesthesia. Level IV, study of nonconsecutive patients without consistently applied reference gold standard.