Ultrasonographic Examination of Inferior Vena Cava Collapsibility Index, Inferior Vena Cava Diameter versus Direct Measurement of Central Venous Pressure for Intravascular Fluid Status Assessment

Background and Objectives: Rapid and accurate assessment of intravascular fluid status is critical in postoperative and critically ill patients. Central venous pressure (CVP) monitoring is invasive and associated with complications. Ultrasonographic assessment of inferior vena cava (IVC) diameter and collapsibility index (IVC-CI) provides a potential noninvasive alternative. This study aimed to determine the correlation between IVC diameter and CVP, and between IVC-CI and CVP.

Methods: A cross-sectional study was conducted in 30 mechanically ventilated postoperative ICU patients with a CVP catheter in situ. IVC diameters were measured using ultrasound, collapsibility index was calculated, and CVP was measured by manometer. Correlations were analyzed using Spearman’s test.

Results: Mean CVP was 10.97 ± 1.79 cm H2O. Mean maximum IVC diameter was 1.24 ± 0.16 cm, minimum diameter 1.06 ± 0.15 cm, and collapsibility index 0.14 ± 0.04. There was a strong positive correlation between CVP and maximum IVC diameter (r = 0.896, p < 0.001). A negligible, nonsignificant negative correlation was found between CVP and IVC-CI (r = -0.119, p = 0.532).

Conclusion: Maximum IVC diameter showed a strong correlation with CVP and may serve as a reliable noninvasive surrogate for assessing fluid status. IVC collapsibility index showed poor correlation with CVP.