Choi YA, et al. - Authors performed a prospective, observational study evaluating the changes in ultrasound measurements of the inferior vena caval index (IVCI), the aorta diameter/IVC diameter index (Ao/IVCD), and the aorta area/IVC area index (Ao/IVCA) during fluid administration in children requiring intravenous fluid administration. In this work, Ao/IVCA exhibited better correlations with the volume of fluid administered than IVCI and Ao/IVCA. For assessing the effects of fluid administration, Ao/IVCA could be a promising index.