Inferior Vena Cava Diameter and Collapsibility Index: A Practical Non-Invasive Evaluation of Intravascular Fluid Volume in Critically-Ill Patients
Prasert Thanakitcharu MD*, Marisa Charoenwut MD*, Napha Siriwiwatanakul MD**
Affiliation : * Division of Nephrology, Department of Medicine, Rajavithi Hospital, College of Medicine, Rangsit University, Bangkok, Thailand ** Division of Cardiology, Department of Medicine, Rajavithi Hospital, College of Medicine, Rangsit University, Bangkok, Thailand
Background : Assessment of intravascular volume status is an essential parameter for the diagnosis and management of
critically-ill patients. Generally, central venous pressure (CVP), which is an invasive measure, has been recommended for
this purpose. Since CVP has been associated with many complications, inferior vena cava diameter and collapsibility index
(IVC-CI) were used in the present study to evaluate the intravascular volume status of critically-ill patients at Rajavithi
Hospital.
Objective : To conduct a prospective, cross-sectional study to evaluate the IVC diameter as a guidance for estimating the
volume status in critically-ill patients by bedside ultrasonography, focusing on correlations between CVP and IVC-CI and IVC
diameter.
Material and Method: Critically-ill patients who had been placed with a functioning central venous catheter were prospectively
enrolled. Evaluation of intravascular volume status was performed by bedside ultrasonography to measure the IVC diameters
(IVCD), both end-inspiratory (iIVCD) and end-expiratory (eIVCD). The IVC collapsibility indices (IVC-CI) were calculated
by an equation and then were compared with the CVP values.
Results : Of the 70 enrolled patients, with a mean age of 63.8 + 1.9 years, 64.3% were intubated. The most common indication
of ICU admission was sepsis with hemodynamic instability (80.0%). The volume status of patients was stratified by their CVP
levels as hypovolemic 15.7%, euvolemic 32.9% and hypervolemic 51.4% which correspond with the IVC-CI of 45.69 +
16.16%, 31.23 + 16.77%, and 17.82 + 12.36% respectively (p < 0.001). The highest significant correlation was found
between the CVP and IVC-CI (r = -0.612, p < 0.001). In addition, there was a significant correlation between CVP and iIVCD
(r = 0.535, p < 0.001); and between the CVP and mean IVCD (r = 0.397, p = 0.001).
Conclusion : The present study supported the correlation between CVP and IVC-CI. The authors conclude that the IVC-CI
can provide a useful guide for noninvasive intravascular volume status assessment of critically-ill patients.
Keywords : Central venous pressure, Inferior vena cava diameter, Collapsibility index, Intravascular fluid volume, Ultrasonography
