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

PurposeWe investigated the effects of the beach-chair position and induced hypotension on regional cerebral oxygen saturation (rSO2) in patients undergoing arthroscopic shoulder surgery by using near-infrared spectroscopy.MethodsTwenty-eight patients scheduled for arthroscopic shoulder surgery were enrolled prospectively. After induction of anesthesia, mechanical ventilation was controlled to maintain Paco2 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 rSO2 was measured by use of near-infrared spectroscopy. MAP and rSO2 were recorded at the following times: before induction (T0), immediately after induction (T1 [baseline]), after beach-chair position (T2), immediately after induced hypotension (T3), 1 hour after induced hypotension (T4), and after supine position at the end of surgery (T5). Cerebral desaturation was defined as a reduction in rSO2 to less than 80% of baseline value for 15 seconds or greater.ResultsA total of 27 patients were evaluated until the end of this study. The MAP at T2 was significantly lower than that at T1. The MAP values at T3 and T4 were significantly lower than those at T1 and T2. The rSO2 at T2 was significantly lower than that at T1. Unlike the pattern of change in the MAP, there was no additional decrease in rSO2 at T3 and T4. There were 2 patients who had an episode of cerebral desaturation.ConclusionsThe beach-chair position combined with induced hypotension significantly decreases rSO2 in patients undergoing shoulder arthroscopic surgery under general anesthesia.Level of EvidenceLevel IV, study of nonconsecutive patients without consistently applied reference gold standard.