Validation of Minimally Invasive Ultrasound Indicator Dilution Technique in Critically Ill Children

A novel method to measure cardiac index based on ultrasound indicator dilution technology (UIDT) has been developed by Transonic Systems Inc. (Ithaca, NY, USA). The method overcomes many of the limitations that have plagued the existing techniques used to measure cardiac index in critically ill children. In the proposed investigation, the investigators hope to validate a novel application of an existing technology in critically ill infants and children. The primary aim of this study is to determine the accuracy of cardiac index measured by UIDT when compared to the gold-standard Fick technique. The primary hypothesis is that the average of three consecutive measurements of cardiac index by UIDT will be accurate when compared to the Fick technique. Secondary aims will be to determine the precision of the measurement, the feasibility of the technique with regards to time required and any complications encountered. An exploratory secondary aim of this study is to determine whether central blood volume (CBV) derived from indicator transit time (ITT) correlates with central venous pressure (CVP) and echocardiography derived measures of preload.