Methods in pharmacology: measurement of cardiac output

Abstract

Many methods of cardiac output measurement have been developed, but the number of methods useful for human pharmacological studies is limited. The 'holy grail' for the measurement of cardiac output would be a method that is accurate, precise, operator independent, fast responding, non-invasive, continuous, easy to use, cheap and safe. This method does not exist today. In this review on cardiac output methods used in pharmacology, the Fick principle, indicator dilution techniques, arterial pulse contour analysis, ultrasound and bio-impedance are reviewed.

© 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.

Figures

Figure 1

Graphical description of the Fick principle. Oxygen enters the lungs (VO2) and is transported to peripheral tissue of the body (CvO2–CaO2). At the same time carbon dioxide produced by the rest of the body (CaCO2–CvCO2) is cleared by the lungs (VCO2). From these concentrations blood flow can be calculated using the formula described in the text

Figure 2

Measurement of cardiac output with the use of carbon dioxide rebreathing

Figure 3

Indicator dilution to measure cardiac output. A dye solution or cold saline is injected and detected by a (dye or thermal) sensor downstream of the injection site. The dilution signal is fed to a cardiac output device. To compute cardiac output the dose injected is divided by the area under the indicator dilution curve. The inset shows the difference in temperature changes for two different locations of detection (see text)

Figure 4

Schematic diagram of the working principle of the continuous thermodilution method

Figure 5

General working principle to estimate cardiac output by pulse contour analysis. A pressure signal is conducted from the pressure sensor to a pulse contour cardiac output device. Together with either calibration values obtained by transpulmonary thermodilution (PiCCO) or lithium dilution (LidCO) and personal patient data, the algorithm estimates aortic flow over a certain interval. This is shown on the device as cardiac output

Figure 6

Effects of dampened radial artery pressure on LidCO pulse contour output of an individual patient. Upper panel systolic (Sys), diastolic (Dia) and mean (MAP) radial artery pressure (Prad). Bottom panel cardiac output by PulseCO (CCO). Sys (); MAP (); Dia ()

Figure 7

Transoesophageal probe geometry. Blood flow velocity is measured by the Doppler beam using the well known Doppler principle. Aortic diameter is determined by the echographic beam by measuring the distance between the backward scatter of the proximal and distal aortic wall. From this distance the cross sectional area of the aorta is calculated