Measurement of Cardiac Output

This chapter examines a cornerstone of critical care medicine: the measurement and monitoring of cardiac output (CO). A key focus is placed on the relevance of CO and clinical decision-making in intensive care setting. The concepts of normalization of CO to body size and fundamentals such as the Fick principle are discussed. Expanding upon these core concepts, indicator dilution methods and thermodilution techniques with their general concepts and sources of variability are explored and applied to clinical practice. The indirect Fick method is then outlined and its clinical applications. With the evolution of critical care medicine, emphasis has been placed on ability to measure CO by using a minimally invasive approach. Pulse contour analysis and the technology available to monitor CO such as Vigileo-FloTrac system, LiDCO plus system, and PiCCO system are reviewed; their clinical relevance is outlined. Echocardiographic techniques (transesophageal and transthoracic) of estimating CO have been described. The chapter concludes with analysis of methods to assess changes in thoracic volume and their relation to CO: thoracic bioimpedance and thoracocardiography.