Abstract Coronary arterial bypass graft (CABG) and valve replacements are open-heart surgeries that are performed on 400,000 Americans each year. The average age of cardiac surgery patients is early 60s, with 52% over the age of 65, and 8% over the age of 80. Octogenarians are increasingly being referred for cardiac surgery, because the aging population is increasing rapidly, and they still benefit enough from CABG to improve long term survival despite higher risk. However, they also have longer post-operative stays in ICU and hospital, and higher rates of ICU readmission. Unexplained hypotension in this population is of particular concern during recovery, because although pressures are routinely measured continuously, discrimination between proper treatment courses requires an additional measure of heart volumes. The previous standard for volume management (a partially implanted Pulmonary Artery Catheter, or PAC) is now considered too risky for prophylactic implantation due to the added risks of another invasive procedure, infection, lack of evidence that it changes outcomes. Without information on volume status, multiple day recovery with only minimal bedside hospital staff present makes the proper diagnosis and rapid treatment of unexplained hypotension tricky. In the older cardiac surgery patient, age-related modifications in cardiac morphology result in decreased contractile reserve, reduced compliance, and blunted inotropic response. This leads to hypotensive situations where the proper diagnosis of cardiac damage or weakness can be confused with low volume status (hypovolemia) and reduced vessel compliance requiring exploratory surgery. All unsure staff in this situation prudently call for an echo, the resident fellow, or other available cardiovascular specialists to infer what the volume is while the patient’s hypotensive state persists, increasing risk. BSM proposes to modify the ubiquitously placed pericardial drain to discriminate among these two states without a PAC, by using a novel, clinically-validated volume measurement, empowering staff to take the proper clinical course of action quickly to stabilize elderly patients.

Project Narrative There are over 400k cardiac surgeries a year in the US that have a high incidence of morbidity (~36%) including hypotension and hypovolemia leading to further cardiac and kidney complications. Accurate and swift differential diagnosis for these conditions requires knowledge of pressures and blood volumes, but invasive volume measurement also increases morbidity, and non-invasive measures are inaccurate or expensive (echo).