Inferior Vena Cava Collapsibility Index and Central Venous Pressure for Fluid Assessment in the Critically Ill Patient

To determine the correlation of sonographic evaluation of inferior vena cava diameter and its collapsibility index with central venous pressure in both spontaneously breathing and mechanically ventilated patients in surgical ICU. Study Design: Cross-sectional study.Surgical ICU, Lahore General Hospital from November 2020 to May 2021.All patients above 18 years of age, who had central venous catheter placed, were included in the study. Patients with raised abdominal pressure, pregnancy, morbid obesity, heart diseases, and those unable to lie in supine position, were excluded. For inferior vena cava (IVC) measurement, IVC was visualised using curvilinear probe of ultrasound machine. Minimum and maximum diameters of inferior vena cava were calculated in every respiratory phase. IVC collapsibility index was expressed in percentage. Central venous pressure (CVP) was recorded soon after IVC measurement, using manometer.Total number of patients was 126. A significant correlation was seen between IVC measurements (inferior vena cava diameters and the collapsibility index) and CVP, (p<0.001), but the regression coefficients were less in patients who were mechanically ventilated (r=0.779 for IVC maximum diameter and -0.725 for collapsibility index) than the patients who were breathing spontaneously (r=0.850 for IVC maximum diameter and -0.899 for collapsibility index) Conclusion: Evaluation of IVC diameter and its collapsibility index is an easy and non-invasive method to evaluate intravascular volume status of critically ill patients. Its use is more helpful in patients who are spontaneously breathing than those who are mechanically ventilated. Key Words: Central venous pressure, Fluid status, Inferior vena cava diameter.