Delirium, Intraoperative Cerebral Perfusion and EEG Abnormalities After Total Hip Arthroplasty

All prospective patients will be given a copy of the informed consent which explains the details and responsibilities of the study. Each patient will have a preoperative baseline 3D-CAM and MOCA to document preoperative cognitive function and possible criteria for exclusion. 1. The 3D -Confusion Assessment Method (CAM) test is a clinician evaluation and algorithm for the binary determination of presence or absence of delirium. 2. Montreal Confusion Assessment (MOCA) - to be given preoperatively to determine if element of pre-existing cognitive impairment Intraoperatively each patient will have a NIR Optode patch placed to measure intraoperative cerebral blood flow and oxygen extraction fraction and cerebral metabolic rate of oxygen consumption. A non-invasive frontal EEG patch will be placed prior to or at the start of anesthesia. Anesthetic depth will be measured using the SEDline® by Masimo. Continuous raw EEG, spectral edge, compressed spectral analysis and percentage suppressed will be recorded from the SEDline® monitor. The investigators will be drawing blood from patients who agree to participate in the study. Preoperative blood sampling will be done while the investigators place the intravenous line, or if present, from an arterial line. If a spinal anesthetic is being used, 5 mL of cerebral spinal fluid (CSF) will be collected at the time of dural puncture prior to the administration of the neuraxial blockade. Members of the research team will administer 3D-CAM testing on post-operative days 1 and 2.