Postoperative Delirium in Hip Arthroplasty Patients

Specific circulating microRNA's have been identified in patients with neurological diseases or deficits, and specifically those with neurodegenerative conditions. Furthermore, available evidence primarily in pre-clinical / animal models supports the hypothesis that post-surgical/anesthesia - induced neuroinflammation leads to post-operative cognitive decline or dysfunction. The investigators hypothesize that specific circulating microRNA's involved in the pro-inflammatory response to surgery/anesthesia are a suitable biomarker of Delirium and/or POCD in surgical hip-arthroplasty patients. However, it is also possible that microamboli during the surgical procedure could contribute to these neurologic outcomes. Therefore, in addition to analyzing microRNA levels (our primary target), the investigators propose to monitor cerebral vascular flow during the surgery to possibly identify microambolic events using Transcranial Doppler. Overall, our overarching goal is to identify novel early clinical indicators of cognitive dysfunction (e.g. Delirium and POCD). The study will include preoperative-postoperative trajectory as well as the value of using subjects as self-controls with appropriate longitudinal analyses of cognition. There are many factors that are potential confounders in relation to cognitive decline and incident dementia. There are key characteristics and events: * illnesses requiring hospitalization, that could potentially accelerate cognitive decline or worsen clinical dementia rating * which anesthetic agents are administered for the surgical procedure * intra-operative adverse events (anesthesia/surgery related, cerebral hypoxia, hypotension/hypertension, blood loss) * patient factors (age, education, comorbidity) * physiologic factors (inflammation,micro-embolization, blood-brain barrier function); * perioperative factors (medications, sleep, complications) * postoperative factors (rehabilitation, depression, social support)