Optimal support of critically ill surgical patients with cardiovascular dysfunction requires that the bedside clinician have both a clear understanding of basic cardiovascular physiology and thorough knowledge of the information available from invasive hemodynamic monitors, including the advantages and pitfalls of each system. Assessment of hemodynamic function in underperfused patients should start with a quantitative assessment of global cardiovascular function. Global variables can be flow derived (e.g., cardiac output), pressure derived (e.g., systolic blood pressure), or both (e.g., ventricular stroke work and power). Any assessment consistent with inadequate global hemodynamic performance should be followed by analysis of the independent determinants of cardiovascular function. These independent determinants include heart rate, preload, afterload, and myocardial contractility. Invasive hemodynamic monitors allow the bedside clinician to measure and quantitate various combinations of global performance and the determinants of cardiac function depending on the monitoring system employed. Central venous lines enable measurement of central venous pressure but limited measure of right ventricular preload. Pulmonary artery catheters offer information pertaining to several global measures and independent determinants. Devices that depend on pulse contour wave analysis, when coupled with a central venous catheter, can measure cardiac output and preload in the context of measurements of stroke volume. However, being invasive, each device carries some degree of risk to the patient, and each monitoring technique employed via these devices carries pitfalls in both measurement and interpretation. It is incumbent upon the bedside clinician to understand the physiologic derangements affecting the patient and the utility and pitfalls of the information available from each device when selecting monitoring systems to be used in any given patient and the supportive therapy that ensues.
This review contains 3 figures, 1 table, and 28 references.
Key words: afterload, cardiac output, central venous catheter, hemodynamic monitor, myocardial contractility, perfusion, preload, pulmonary artery catheter, pulse contour analysis, stroke volume, stroke volume variability, stroke work, ventricular power
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