ORIGINAL ARTICLE   Free access

Minerva Anestesiologica 2019 May;85(5):514-21

DOI: 10.23736/S0375-9393.18.13041-0

Copyright © 2018 EDIZIONI MINERVA MEDICA

language: English

Size and shape of the inferior vena cava before and after a fluid challenge: a pilot study

Daniele G. BIASUCCI ¹ ✉, Alessandro CINA ^{2, 3}, Maria CALABRESE ⁴, Maria E. ANTONIUCCI ⁴, Carlo CAVALIERE ⁵, Francesca BEVILACQUA ⁴, Franco CAVALIERE ^{3, 4}

¹ Intensive Care Unit, “A. Gemelli” University Hospital Foundation IRCCS, Rome, Italy; ² Department of Radiology, A. Gemelli Policlinic IRCCS Foundation, Rome, Italy; ³ Unit of Cardiac Anesthesia and Cardiac Surgical Intensive Care, A. Gemelli Policlinic IRCCS Foundation, Rome, Italy; ⁴ Sacred Heart Catholic University, Rome, Italy; ⁵ Department of Sense Organs, La Sapienza University, Rome, Italy

BACKGROUND: Recent meta-analyses failed to support the reliability of ultrasound assessment of the inferior vena cava (IVC) to predict fluid responsiveness. However, the techniques utilized were heterogeneous. We hypothesized that the variability of the elliptic section and caliber of the IVC along its course may influence ultrasound evaluation. Therefore, we investigated IVC size and shape at four levels, before and after a fluid challenge.
METHODS: Twenty mechanically-ventilated adult patients who received a fluid challenge after cardiac surgery were enrolled. They were regarded as responders if the cardiac index increased more than 15%. Before and after the fluid challenge, IVC anteroposterior (AP) and lateral (LA) diameters, the flat ratio, and the distensibility index were assessed by ultrasound just above the iliac veins, at the confluence of the renal veins, before the confluence of the hepatic veins (where blood flow velocity was also measured), and after it.
RESULTS: At all levels, IVC section was elliptical, so that IVC diameters varied between a minimum and a maximum according to the measurement angle. Such interval increased in correspondence of the renal veins, where IVC section was more eccentric. The distensibility index was higher when assessed on AP diameters. After the fluid challenge, non-responders showed a diffuse increase of AP diameters, whereas responders showed an increase of blood velocity before the confluence of the hepatic veins.
CONCLUSIONS: The elliptic section should be considered when assessing IVC size. AP diameters are shorter and more affected by the respiratory cycle. After a fluid challenge, an increase of blood velocity associated with unchanged AP diameters may suggest fluid responsiveness.

KEY WORDS: Vena cava, inferior; Resuscitation; Critical care; Cardiac Surgical Procedures; Hypovolemia; Ultrasonography