Estimating mean circulatory filling pressure in clinical practice: a systematic review comparing three bedside methods in the critically ill

The bedside hemodynamic assessment of the critically ill remains challenging since blood volume, arterial–venous interaction and compliance are not measured directly. Mean circulatory filling pressure (P_mcf) is the blood pressure throughout the vascular system at zero flow. Animal studies have shown P_mcf provides information on vascular compliance, volume responsiveness and enables the calculation of stressed volume. It is now possible to measure P_mcf at the bedside. We performed a systematic review of the current P_mcf measurement techniques and compared their clinical applicability, precision, accuracy and limitations. A comprehensive search strategy was performed in PubMed, Embase and the Cochrane databases. Studies measuring P_mcf in heart-beating patients at the bedside were included. Data were extracted from the articles into predefined forms. Quality assessment was based on the Newcastle–Ottawa Scale for cohort studies. A total of 17 prospective cohort studies were included. Three techniques were described: P_mcf hold, based on inspiratory hold-derived venous return curves, P_mcf arm, based on arterial and venous pressure equilibration in the arm as a model for the entire circulation, and P_mcf analogue, based on a Guytonian mathematical model of the circulation. The included studies show P_mcf to accurately follow intravascular fluid administration and vascular compliance following drug-induced hemodynamic changes. Bedside P_mcf measures allow for more direct assessment of circulating blood volume, venous return and compliance. However, studies are needed to determine normative P_mcf values and their expected changes to therapies if they are to be used to guide clinical practice.