Background: Estimating volume status in infants and neonates is challenging. Global end-diastolic volume (GEDV) and dynamic variables of preload, such as pulse pressure variation (PPV), may be alternative variables for estimating cardiac preload and fluid responsiveness. Therefore, we designed the present study to evaluate whether GEDV and PPV are suitable variables of preload and fluid responsiveness during rapidly changing loading conditions in a pediatric animal model.
Methods: Nineteen anesthetized and mechanically ventilated piglets (6.5 +/- 0.8 kg) were studied during different loading conditions. Hemodynamic measurements, including central venous pressure, pulmonary capillary wedge pressure, PPV, GEDV, and cardiac output derived by transpulmonary thermodilution, cardiac output, and stroke volume index obtained by pulmonary artery thermodilution were performed at normovolemia, and after fluid administration, with 25 mL/kg of hydroxylethyl starch 6%.
Results: There was a significant percentage change of GEDV after volume loading (25% +/- 17%) that resulted in significant changes of all hemodynamic variables except of heart rate and systemic vascular resistance index. GEDV was the only preload variable that significantly correlated with volume-induced percentage change in stroke volume index (r = -0.61, P = 0.005). Area under the receiver operating characteristic curve was 0.8 for GEDV (P < 0.02) and 0.6 for PPV (P = ns).
Conclusions: In this pediatric animal model, GEDV derived from transpulmonary thermodilution was a reliable indicator of cardiac preload. Moreover, GEDV but not PPV, central venous pressure and pulmonary capillary wedge pressure accurately reflected fluid responsiveness.