Device placed on the subject preoperatively in the holding room and continued postoperatively into the Cardiac Intensive Care Unit (ICU).

The device will be placed on the subject and monitoring started in the holding room on the morning of surgery. Monitoring will continue postoperatively until the pulmonary artery catheter (PAC) is removed (Standard of Care) or discharged, or at study team discretion. At Intensive Care Unit (ICU) admittance and again 3 hours later a straight leg raise will be done to monitor for changes in hemodynamics.

Cardiac output values correlation of cardiac output between the PA catheter as assessed by the CCO and the VitalStream - the amount of blood pumped by the heart minute - Cardiac output is calculated by multiplying stroke volume with heart rate - Cardiac output in humans is generally 5-6 L/min in an at-rest to more than 35 L/min in elite athletes during exercise. HR is determined by signals from the sinoatrial node, which automatically depolarizes at an intrinsic rate of 60 to 100 times each minute - Low-output symptoms are caused by the inability of the heart to generate enough cardiac output. This leads to reduced blood flow to the brain and other vital organs

correlation of blood pressure continuously being monitored by the Vitalstream and the subjects indwelling arterial line

Assessment of fluid responsiveness using a passive leg raising test (PLR) maneuver, within 1 hour of ICU admission and 3 hours later. We will access fluid challenge using the fluid challenge timer feature on the VitalStream, by doing serial assessments before and after each passive leg raising test.

PLR is a simple bedside technique that can be used to assess fluid responsiveness. This maneuver can be used as a pseudo-fluid challenge of an approximately of 150-300 mL by placing patient head down flat and feet up at a 45° angle. Blood from the lower extremities translocate to intrathoracic compartment where the right and left ventricular preload increases and if the patient is responsive increases SV and cardiac output. An increase in SV of more than 10% indicates the patient is preload responsive with the high sensitivity and specificity.