Sonographic evaluation of intravascular volume status: Can internal jugular or femoral vein collapsibility be used in the absence of IVC visualization?

Abstract

Introduction: Inferior vena cava collapsibility index (IVC-CI) has been shown to correlate with both clinical and invasive assessment of intravascular volume status, but has important limitations such as the requirement for advanced sonographic skills, the degree of difficulty in obtaining those skills, and often challenging visualization of the IVC in the postoperative patient. The current study aims to explore the potential for using femoral (FV) or internal jugular (IJV) vein collapsibility as alternative sonographic options in the absence of adequate IVC visualization.

Methods: A prospective, observational study comparing IVC-CI and Fem- and/or IJV-CI was performed in two intensive care units (ICU) between January 2012 and April 2014. Concurrent M-mode measurements of IVC-CI and FV- and/or IJV-CI were collected during each sonographic session. Measurements of IVC were obtained using standard technique. IJV-CI and FV-CI were measured using high-frequency, linear array ultrasound probe placed in the corresponding anatomic areas. Paired data were analyzed using coefficient of correlation/determination and Bland-Altman determination of measurement bias.

Results: We performed paired ultrasound examination of IVC-IJV (n = 39) and IVC-FV (n = 22), in 40 patients (mean age 54.1; 40% women). Both FV-CI and IJV-CI scans took less time to complete than IVC-CI scans (both, P < 0.02). Correlations between IVC-CI/FV-CI (R(2) = 0.41) and IVC-CI/IJV-CI (R(2) = 0.38) were weak. There was a mean -3.5% measurement bias between IVC-CI and IJV-CI, with trend toward overestimation for IJV-CI with increasing collapsibility. In contrast, FV-CI underestimated collapsibility by approximately 3.8% across the measured collapsibility range.

Conclusion: Despite small measurement biases, correlations between IVC-CI and FV-/IJV-CI are weak. These results indicate that IJ-CI and FV-CI should not be used as a primary intravascular volume assessment tool for clinical decision support in the ICU. The authors propose that IJV-CI and FV-CI be reserved for clinical scenarios where sonographic acquisition of both IVC-CI or subclavian collapsibility are not feasible, especially when trended over time. Sonographers should be aware that IJV-CI tends to overestimate collapsibility when compared to IVC-CI, and FV-CI tends to underestimates collapsibility relative to IVC-CI.

Keywords: Femoral vein; hemodynamic resuscitation; inferior vena cava; intravascular volume status assessment; intensive care unit; internal jugular vein; point-of-care testing; portable ultrasound; venous collapsibility index.

Conflict of interest statement

Conflict of Interest: None declared.

Figures

Figure 1

Determination of IVC collapsibility. At right, transducer position is demonstrated; anatomic midline is indicated by the dashed line. At left, M-mode tracing of the IVC. The white vertical line marks the line of measurement across the long-axis of the IVC. The hepatic veins (HV) and right atrium (RA) are visualized in this standard window. Brackets (left, bottom) denote the minimal (dmin) and maximal (dmax) diameters of the IVC measured over the entire respiratory cycle

Figure 2

Technique for determination of IJ collapsibility. A transverse view of the IJ vein is taken using the M-mode; maximal and minimal diameters are measured then normalized to % collapsibility using the described methods

Figure 3

Technique for determination of femoral vein collapsibility. A transverse view of the femoral vein is obtained with the M-mode; maximal and minimal diameters are measured and normalized to %-collapsibility using the described methods

Figure 4

Regression plot of IVC-CI versus IJV-CI (left); Bland-Altman plot of IVC-CI versus IJV-CI (right)

Figure 5

Regression plot of IVC-CI versus FV-CI (left); Bland-Altman plot of IVC-CI versus FV-CI (right)