Ultrasonographic measurement of inferior vena cava collapsibility index and its correlation to central venous pressure in adult critically ill patients

Abstract

Background Central venous pressure (CVP) is currently one of the most widely used parameters for the determination of volume status in critically ill patients. To measure CVP, a central venous catheter must be inserted. This process is invasive, requires complex training, and has many complications such as bleeding, traumatic pneumothorax, and infection. Also it may be contraindicated in the presence of coagulation abnormalities which are not a rare finding in critically ill patients. Transabdominal ultrasonographic determination of inferior vena cava (IVC) collapsibility index (CI) can provide a rapid, noninvasive, easy, and reproducible method of determination of volume status in critically ill patients, which avoids the risk and complications of invasive central venous catheterization. Patients and methods The prospective study was carried out in Zagazig University Hospital. A total of 86 patients who were admitted to trauma and surgical emergency ICU at Zagazig University Hospitals were eligible for enrollment in this study over the period of 2 years (October 2015–October 2017). Each patient had simultaneous measurement of CVP and IVC-CI on four different sessions; the first was on admission, the second was 6 h after admission, the third was 12 h after admission, and the fourth was 24 h after admission. The patient sample was divided into two subgroups based on the mode of ventilation and CVP value to compare the strength of correlation between caval index and CVP value in the two groups. Results Our study showed that IVC-CI has significant negative correlation with CVP value (r=−85, P˂0.001 at 95% confidence interval) and it is better correlated with mean arterial blood pressure and lactate clearance as compared with CVP. However, it correlated better in spontaneously breathing patients (r=−0.86, P˂0.001) than in mechanically ventilated patients (r=−0.84, P˂0.001). IVC-CI has shown to correlate better with CVP value in lower values (˂10 cmH2O) (r=−0.8, P˂0.001) than in higher values (≥10 cmH2O) (r=−0.6, P˂0.001). We also concluded an IVC-CI cutoff value of 29% to discriminate between CVP values less than 10 cmH2O and values more than or equal to 10 cmH2O with high sensitivity (88.6%) and specificity (80.4%). Conclusion IVC-CI has a strong inverse relationship with CVP which is more pronounced at low CVP values. Point-of-care ultrasonographically measured IVC-CI is very likely to be a good alternative to CVP measurement with a high degree of precision and reproducibility