Comparison of central venous pressure and the inferior vena cava/aorta diameter index for evaluation of body fluid status

Purpose: Central venous pressure (CVP) is used almost universally to evaluate patient body fluid status. But historical and more recent data suggest that this approach may be flawed. In this study, we compared the accuracy of CVP versus the inferior vena cava/aorta diameter index (IVC/Ao index), a new approach to assessing body fluid status. Methods: This study was carried out prospectively with subjects over 18 years of age who visited the emergency department between November 2010 and January 2011. A central venous catheter (CVC) was inserted into patients undergoing computed tomography (CT). IVC and aortic diameter were measured below the renal vein using the CT in axial view. To determine the exact CVP, we measured the distance from the tip of the CVC to the superior vena cava/right atrium (SVC/RA) junction in coronal and axial CT views, and placed the tip of a CVC at the SCV/RA junction. We analyzed the correlation between the CVP, IVC diameter and the IVC/Ao index. Results: A total of 65 patients were enrolled in this study. The mean CVP was 9.25±5.99 mmH2O, IVC diameter was 1.456±0.568 cm and IVC/Ao index was 0.854± 0.316. The correlation coefficient for CVP and IVC diameter was 0.625 (p<0.01) and for CVP and IVC/aorta index it was 0.711 (p<0.01). Coefficient of variations (CVs) of the IVC/Ao index was 0.76 at CVP 5 mmH2O and 0.14 at CVP 17 cmH2O. The correlation coefficient for CVP and IVC/Ao index in the group with a CVP result of less than 8 cmH2O was 0.330, and in the group with a CVP result greater than 8 cmH2O, it was 0.660 (p<0.01). Conclusion: The CVP results had a higher correlation to the IVC/aorta index than to the IVC diameter. The coefficient of variant (CV) tended to increase as CVP decreased. It is best not to use a single value of CVP or IVC/Ao index to evaluate the body fluid state, as some kind of dynamic parameter should be used.