Correlation of Bedside Ultrasonographic Measurement of IVC Diameter and Caval Index with CVP in Spontaneously Breathing and Mechanically Ventilated Patients

Evaluation of intravascular volume status in critically ill patients is very essential. Central venous catheter insertion is needed to determine the CVP which is used to detect the fluid need. Complications such as arrhythmias, pneumothorax, haemothorax, hematoma, infection and thrombosis may occur with catheter insertion [1]. Sonographic evaluation of the IVC diameter and its usefulness in evaluating the volume status are studied and documented [2]. Ultrasound imaging has several advantages; it is simple, noninvasive and can be used for repeated assessment. Ultrasound units are present in most intensive care units to routinely perform the focused assessment sonography in critically ill patients [3]. The IVC is a thin-walled and compliant vessel. By changing its diameter, it adjusts to the body's volume status. Inspiration generates negative pressure which results in increase venous return, subsequently collapsing the IVC. Expiration decreases venous return and the IVC diameter returns to its original value. In cases of decreased intravascular volume, the degree of IVC collapse will be proportionally higher than in cases with increased intravascular volume. The IVC collapsibility is determined by the calculation of the caval index (%) [4]. In this study, we aimed to detect the correlation between IVC diameter and caval index with CVP in spontaneously breathing and mechanically ventilated patients to provide IVC assessment as a guiding method in evaluation of the intravascular volume status.