This is a single center prospective observational study to compare QPlus parameter measurements in arterial and venous blood samples collected in parallel from patients undergoing cardiac surgery.

In this single center prospective observational study, 40 cardiac surgery subjects will enrolled, each with parallel artrial and venous samples collected at 3 time points to yield 120 matched samples for analysis on the Quantra System with the QPlus Cartridge.

Inclusion Criteria:

• Subject is scheduled for cardiac surgery, utilizing cardiopulmonary bypass, or including placement of a ventricular assist device
• Subject is ≥18 years
• Subject or subject's legally authorized representative is willing to participate and he/she has signed a consent formr.

Exclusion Criteria:

• Subject is younger than 18 years
• Subject is pregnant
• Subject is incarcerated at the time of the study
• Subject is affected by a condition that, in the opinion of the surgical team, may pose additional risks
• Subject, or subject's legally aurthorized representative is able to provide written informed consent

Adult males and females undergoing cardiac surgery