Critical Care: Imaging in Critical Illness |

Inferior Vena Cava Flat Ratio as a Predictor of Concordance or Discordance Between Subcostal and Transhepatic Measurements of Collapsibility FREE TO VIEW

Rian Shah, MD; Rory Spiegel, MD; Christina Lu, MD; Sahar Ahmad, MD
Author and Funding Information

Stony Brook University Hospital, Stony Brook, NY

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;150(4_S):293A. doi:10.1016/j.chest.2016.08.306
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SESSION TITLE: Imaging in Critical Illness

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM

PURPOSE: Ultrasound imaging of inferior vena cava (IVC) collapse from the subcostal sonographic window is utilized by intensivists to predict blood pressure response to volume resuscitation. Often the subcostal window is unobtainable and the transhepatic view from the right mid axillary space is the only available window. However, the anterior-posterior elliptical pattern into which the IVC collapses, called the IVC flat ratio (Naruse, 2007), may limit this view’s clinical utility. This study aimed to (1) describe concordance between subcostal and transhepatic measurements to predict fluid responsivity (cIVCsc and cIVCth respectively) and (2) describe how the IVC flat ratio correlates to concordance.

METHODS: A sample of 66 spontaneously breathing patients in a large university hospital were enrolled. Measurement of the IVC maximum (Dmax) and minimum diameter (Dmin) was successfully recorded in 55 patients from both the subcostal and transhepatic windows. IVC collapsibility (cIVC) was calculated as Dmax-Dmin/Dmax. The IVC was also successfully visualized in cross section from the subcostal window in 48 of these 55 patients allowing measurement of maximum and minimum diameters of the anterior - posterior (Dap) and medial- lateral (Dml) axes. Flat ratio was calculated at maximum collapse and expressed as Dap/Dml with values > 1 indicating vertical, and < 1 indicating horizontal ellipse shapes.

RESULTS: Fluid responsiveness was defined as cIVCsc > 42% (Airapetian, 2015). In fluid responsive patients (n=16), there was discordance between the two views (paired t- test, p=0.001) in ability to predict fluid responsivity. In fluid non- responsive patients (n=32), there was concordance (p=0.484). 40 of 48 (83%) subjects had a flat ratio value of <1, with the IVC collapsing into a horizontal ellipse. The flat ratio predicted greatest concordance when flat ratio neared 1, and discordance with values greater or less than 1. The transhepatic view was found to have a sensitivity of 0.4, specificity of 0.9, positive predictive value 0.6, and negative predicative value of 0.7 for predicting fluid responsiveness.

CONCLUSIONS: To our knowledge, we are the first to identify that the IVC predominantly collapses into a horizontal ellipse, and that flat ratio can predict concordance. We have also determined that the transhepatic view is less sensitive in predicting fluid responsivity as compared to the current standard subcostal view. In particular, this view is discordant to the subcostal view in fluid responsive patients.

CLINICAL IMPLICATIONS: The transhepatic view alone should not be used to exclude fluid responsivity or deter a physician from administering fluids for hypotension.

DISCLOSURE: The following authors have nothing to disclose: Rian Shah, Rory Spiegel, Christina Lu, Sahar Ahmad

To the best of our knowledge the transhepatic view of the IVC and Flat Ratio are not currently used in clinical practice and can thus qualify as research.




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