Comparative Analysis of Cerebral Oximetry and Mean Arterial Pressures at the Cerebral Level in the Beach Chair Position

Inclusion Criteria: * Subjects must be undergoing elective shoulder replacement surgery * Subjects must have an ASA class of I or II * Subject is able and willing to sign the informed consent * Subject is 18 years of age or older at time of consent * Subject is not pregnant * Subject is not a prisoner Exclusion Criteria: * Subject has a mental condition that may interfere with the subject's ability to give informed consent or willingness to fulfill the study requirements (i.e., severe mental retardation such that the subject cannot understand the informed consent process, global dementia, prior strokes that interfere with Subject's cognitive abilities, senile dementia, and Alzheimer's Disease) * Subject is younger than 18 years of age at consent * Subject is pregnant * Subject is a prisoner