This course examines cardiac output (CO), a leading measure of hemodynamic stability. The course begins with a close look at the determinants of cardiac output, including a review of terms that were introduced in the previous course, Basics of Hemodynamics, such as preload, and afterload. The course continues with an overview of the physiology of unbalanced CO, using the example of dehydration to illustrate the consequences of hemodynamic instability. The course concludes with a summary of goal-directed therapy, a series of strategies to optimize CO in hemodynamically unstable patients.