This study will involve patients who are planned to have hip or knee replacement surgeries. They will undergo a Transthoracic Echocardiogram study (an ultrasound of the heart) to look for a Patent Foramen Ovale (PFO). A PFO is a hole in the heart that everyone is born with and in most cases eventually closes by adulthood. However, it does not always close in all people. The investigators will compare the participants as two groups - those with a PFO, and those without, and look for differences in delirium in their postoperative stay. This will help us look for an association between postoperative delirium and the presence of a PFO.