The sitting position for shoulder arthroscopic surgery can cause critical hypotension, a reduction in cerebral blood flow and possible cerebral ischemia due to decreased venous return. The aim of this study was to determine the effects of a positional change to the sitting position on the mean arterial pressure (MAP), heart rate (HR) and regional cerebral oxygen saturation (rSO₂) through ECG, invasive blood pressure monitoring and near-infrared spectrometry.

Thirty five patients of ASA class I or II undergoing shoulder surgery were chosen randomly. General anesthesia was administered with sevoflurane and a mixed gas of medical air and oxygen. The MAP, HR, rSO₂ and rate of change in the rSO₂ on the left and right side were measured at the following times: after induction when the MAP and HR were stabilized (baseline), 1, 3, 5, 10, 15 and 20 min after placing the patient in the sitting position.

The MAP decreased significantly at 5, 10, 15 and 20 min after placing the patient in the sitting position. The HR increased significantly at 1 min and 3 min after placing the patient in the sitting position, and decreased significantly at 15 min and 20 min after placing the patient in the sitting position. The rSO2 showed a significant decrease at 5, 10, 15 and 20 min on the left side and at 10 min, 15 min and 20 min on the right side.

The MAP and rSO₂ significantly decreased after placing the patient in the sitting position but there were no neurological complications. However, close monitoring of the MAP and rSO₂ is required in elderly patients or patients with cerebrovascular disease is recommended while the patient is in the sitting position in order to avoid neurological complications.