Estimation of the parameters of cardiac function and of blood volume by arterial thermodilution in an infant animal model

BACKGROUND: Experimental studies in adults and in animals have reported that estimation of the intracardiac volumes by arterial thermodilution is a more reliable method of blood volume estimation than pressure measurement. The objective of this study has been to analyze the values of cardiac function and blood volume in an infant animal model using the arterial thermodilution technique. METHODS: A total of 202 measurements of cardiac output were performed by femoral arterial thermodilution in 38 Maryland piglets weighing between 8 and 16 kg, to determine the normal values of blood volume obtained by arterial thermodilution (PiCCO method) in an infant animal model. The following parameters were measured: blood volume [global end-diastolic volume index (GEDVI), total intrathoracic blood index (ITBI), extravascular lung water index (ELWI), systolic volume index (SVI)] and parameters of cardiac and vascular function [systolic volume index (SVI), cardiac function index (CFI), left ventricular contractility (Dp/dtmax), and systemic vascular resistance index) (SVRI)]. RESULTS: The cardiac index, 4.3 +/- 1.2 l x min(-1) x m(2), was within the normal range. The GEDVI, 198 +/- 48.6 ml x m(2), and ITBI, 574.1 +/- 113.4 ml x m(2), were lower than the normal values reported in adults, whereas the ELWI, 16.3 +/- 5.2 ml x kg(-1), was higher. CONCLUSIONS: Intrathoracic and intracardiac volume values obtained by arterial thermodilution are lower than those considered normal in the adult, whereas the extravascular lung water is higher. These values must be taken into account when the PiCCO method is used in small children.