Purpose of review: Most of our blood volume is contained in the venous compartment. The so-called 'compliant veins' are an adjustable blood reservoir, which is playing a paramount role in maintaining haemodynamic stability. The purpose of this study is to review what is known about this blood reservoir and how we can use this information to assess the cardiovascular state of critically ill patients.
Recent findings: The mean systemic filling pressure (Pmsf) is the pivot pressure of the circulation, and a quantitative index of intravascular volume. The Pmsf can be measured at the bedside by three methods described in critically ill patients. The Pmsf can be modified by the fluid therapy and vasoactive medications.
Summary: The Pmsf along with other haemodynamic variables can provide valuable information to correctly understand the cardiovascular status of critically ill patients and better manage the fluid therapy and cardiovascular support. Future studies using the Pmsf will show its usefulness for fluid administration.