After obtaining written consent to participate, the standard of care arterial line and PA catheter will be placed pre-operatively. The investigators will attach the Nonin pulse oximeter, as a second pulse oximeter probe, to patients undergoing surgical procedures which already require invasive cardiac monitors (arterial line, pulmonary artery catheter, etc). Data from both the traditional invasive cardiac monitors and the Nonin pulse oximeter will be collected as electronic files. Once both files are compiled they will be de-identified.~The investigators will also record medications and IV fluids given during surgery.~The Nonin Pulse Oximeter is clinically marketed for this indication~The investigators will analyze Nonin data for peak and trough variation with respiration, area under the curve, time from trough to peak, and slope, and compare these to data collected from the invasive monitors to look for correlations in clinically important parameters such as blood pressure, central venous pressure, cardiac output, etc.
Data from both the traditional invasive cardiac monitors and the Nonin will be collected simultaneously. The investigators will analyze Nonin data for peak and trough variation with respiration, area under the curve, time from trough to peak, and slope, and compare these to data collected from the invasive monitors to look for correlations in clinically important parameters such as blood pressure, central venous pressure, cardiac output, etc.