Hypovolemia related hemodynamic instability and its complications are common in critically ill patients. The traditional method of volume status estimation is central venous pressure (CVP), which is being replaced by inferior vena cava collapsibility index (IVC-CI) as an easy, inexpensive and non-invasive alternative. The present study is intended to assess the diagnostic accuracy of IVC-CI in determining hypovolemic status in critically ill patients, as compared to CVP. A prospective, diagnostic accuracy assessment study was conducted in 106 critically ill patients and CVP measurements were done from a central venous catheter. Bedside sonography was done to measure the anteroposterior diameter of inferior vena cava (IVCD) at end-inspiration and end-expiration. The formula [(maximum IVCD–minimum IVCD)/ maximum IVCD] x100 was used to calculate IVC-CI. Statistical software SPSS 24.0 was used for analysis and determination of the validity of the test. Of the 106 patients studied, 72 had spontaneous breathing. 46.2% patients had a low CVP value of < 8 cm H₂O. The values of inspiratory and expiratory IVC diameters, and IVC-CI were found to be statistically significant in both the spontaneous and the mechanically ventilated groups. In the spontaneous group, an IVC-CI > 34.8% (sensitivity 76.5%, specificity 100%, positive predictive value 100%, negative predictive value 82.6% and accuracy 88.9%) and in mechanically ventilated patients, IVC-CI > 52.1% (sensitivity 93.3%, specificity 100%, positive predictive value 100%, negative predictive value 95% and an accuracy 97.1%) were obtained as cut-offs. IVC-CI is well validated in determining hypovolemia in critically ill patients.

Keywords: central venous pressure; inferior vena cava collapsibility index; hypovolemia; spontaneously breathing and mechanically ventilated patients.

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Dr Arsha Asok MD DNB

Senior Resident, Department of Anaesthesiology, Government Medical College Thiruvananthapuram