List the techniques / measurements that are available to assess the circulation status of a patient in the intensive care unit.
This question is a "list" question, and thus one should resist the temptation to critically evaluate, or to compare and contrast. A list of techniques is reasonably easy to generate. Specifically, techniques to assess volume-responsiveness are extensively discussed in the section concerned with Fluid Resuscitation, Vasopressors and Inotropes. If one needed to generate a dumb noncomparative list for whatever reason, one should do so in a manner which follows a system of some sort.
Static indices of fluid responsiveness
Dynamic indices of fluid responsiveness
Assessment of circulatory efficacy
Assessment of microcirculation
Marik, Paul E. "Hemodynamic parameters to guide fluid therapy." Transfusion Alternatives in Transfusion Medicine 11.3 (2010): 102-112.