Mean systemic filling pressure is an old concept but a new tool for fluid management

Abstract

Purpose of the review: Most of our blood volume is contained in the venous compartment. The so-called compliant veins are an adjustable blood reservoir that is playing a paramount role in maintaining hemodynamic stability. Several autonomous reflexes govern the capacity of this reservoir. The mean systemic filling pressure (Pmsf) is the pressure in the cardiovascular system when there is no blood flow, and is pressure that can describe the capacitance of the venous reservoir. This pressure can be measured in human patients by both noninvasive or minimally invasive methods. However, the significance of this new hemodynamic variable is still not fully understood. The purpose of this review is to summarize what is known about the venous reservoir and the Pmsf and how we can use this information to assess the cardiovascular state of critically ill patients. Findings: The venous tone is governed by sympathetic reflex, mainly related to baroreceptors via α(alpha)-adrenergic stimulation and to chemoreceptors. The vasoconstriction affects significantly the capacitance of the system by shifting blood between the stress and nonstress volume compartments. The mean systemic filling pressure (Pmsf) is the pivot pressure of the circulation, and a quantitative index of intravascular volume, and it is also governed by the mechanisms that affect the venous tone. Pmsf can be measured at bedside by three methods described in critically ill patients. This pressure can be also modified by fluid therapy and vasoactive medications. Pmsf along with other hemodynamic variables can provide valuable information to correctly understand the cardiovascular status of critically ill patients and better managing fluid therapy and cardiovascular support. Future studies using Pmsf will show its usefulness for fluid administration.