Brief ReportSonographic inferior vena cava/aorta diameter index, a new approach to the body fluid status assessment in children and young adults in emergency ultrasound—preliminary study
Introduction
An accurate assessment of the body fluid status is a significant challenge during every clinical examination. In many disorders, the therapy and its effectiveness depend on appropriate evaluation of body water status, especially in patients hospitalized in the emergency, nephrology, and pediatric departments.
There are many useful methods of evaluating percentage of water incontinence in body tissues, such as clinical examination, biochemical markers, bioimpedance, continuous blood volume measurement, or sonographic inferior vena cava (IVC) diameter assessment. However, all of these methods are burdened with some limitations when used in clinical practice.
The advantages of ultrasound imaging are commonly known and ultrasound units are present in every emergency department (ED) where fast imaging technique is indispensable. Therefore, in this article we concentrated on the last mentioned method of body fluid status assessment. The usefulness of the sonographic assessment of IVC diameter has been proven in patients with impaired kidney function treated with hemodialysis, patients with nephritic syndrome, or patients hospitalized in intensive care wards. Simultaneously, we are aware of some limitations of this method, such as problems with equipment, necessity of comparing results with body surface area (BSA), measurement of IVC diameter during maximal inspiration and expiration (needing cooperation of the patient), and lack of reference values for IVC diameter especially in the pediatric population. For these reasons, we introduce a new sonographic parameter, the “IVC/aorta (Ao) diameter (IVC/Ao) index,” an innovation that is convenient, fast, easy to perform, and effective in the evaluation of body fluid status, especially in EDs.
Section snippets
Part 1
Fifty-two healthy volunteers (students of medicine; 29 women, 23 men), aged between 20 and 25 years, were enrolled into the study. One woman was excluded because of elevated blood pressure values. In the ultrasound examination, we concentrated on assessment of IVC and aorta diameters. The measurements were performed twice, initially at 8 am after 12 hours of fasting (“physiological dehydration” status) and 6 to 8 hours later after intake of 1500 to 2000 mL of fluids or around 70% to 90% of the
Examination technique
The ultrasound examination was taken with the subject in a supine position with the transducer placed underneath the xiphoid process in a longitudinal direction. The IVC diameter was measured beneath the confluence with hepatic veins, where its anterior and posterior wall were parallel (Fig. 1). The IVC diameter was measured during a regular breathing cycle, and the maximum value was recorded. The aorta diameter was taken in a similar way, 5 to 10 mm above the celiac trunk.
Part 1
The measurements were performed in all volunteers. There was a statistically significant increase in body weight before and after fluid intake: 0.74 kg ± 0.65 (P < .00001).
The IVC and aorta diameters significantly increased after fluid intake (P < .05). However, there was no statistically significant difference in aorta diameter if calculated per square meter of BSA (P = .08). When IVC diameter value was calculated in the same way the difference was statistically significant (P = .00004) (Table
Discussion
The accuracy of body fluid status assessment plays a significant role in the diagnostic and therapeutic processes of acute and chronic disorders, influencing their further treatment and final recovery. There are different methods of evaluating body hydration status, but none of them is optimal and all of them have some limitations [1].
From a practical point of view the ideal method should be easy to perform, quick, precise, and repetitive. There are many optimistic reports pointing to the
Conclusions
- 1.
For the healthy population aged 20 to 30 years, we suggest the IVC/Ao index reference value of 1.2 ± 2 SD for SD = 0.17.
- 2.
IVC/Ao index seems to be a very useful parameter for estimating body fluid status and there is necessity of further evaluation of its value in clinical practice especially in the pediatric population.
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