Assessing fluid status with the vascular pedicle width: relationship to IVC diameter, IVC variability and lung comets

Introduction

This study attempts to determine a vascular pedicle width (VPW) cutoff value that identifies a fluid replete state defined as an IVC diameter ≥2 cm and ≤15% respiratory variation.

Methods

In a cross-sectional design, consecutive, critically ill patients underwent simultaneous chest radiographs and ultrasounds. The Research Ethics Committee approved the study.

Results

Eighty-four data points on 43 patients were collected. VPW correlated with IVC diameter (r = 0.64, P ≤0.001) and IVC variation (r = -0.55, P ≤0.001). No correlation was observed between VPW and number of lung comets (r = 0.12, P = 0.26) or positive fluid balance (r = 0.3, P = 0.058). On multivariate linear regression, standardized coefficients demonstrated that a 1 mm increase in IVC diameter corresponded to a 0.28 mm (Beta) increase in VPW. ROC curve analysis yielded an AUC of 0.843 (95% CI = 0.75 to 0.93), P ≤0.001 and provided the best accuracy with a cutoff VPW value of 64 mm (sensitivity 81%, specificity 78%, PPV = 88.5%, NPV = 66%, correct classification rate = 79.6%). See Figure 1.

Figure 1

ROC curve for VPW discriminating fluid repletion by IVC ultrasound.

Conclusion

A VPW value of 64 mm accurately identifies a fluid replete state. Increased extravascular lung water, however, was not relatable to the VPW measurements. The VPW can be confidently used to discriminate fluid repletion from fluid responsiveness.