Ultrasound Derived Inferior Vena Cava Diameter and Collapsibility Index to Predict Central Venous Pressure Prior and After A Fluid Challenge in Spontaneous Breathing Preoperative Patients

Background: Central venous pressure (CVP) is indicator of preload and used to determine intravascular volume status. An invasive method such as central venous catheter placement is required in order to measure CVP. However, it is associated with many complications. Instead, sonographic measurement of inferior vena cava (IVC) represents effective and noninvasive method of estimating CVP and recommendations are provided by the American Society of Echocardiography (ASE). There are various methods to calculate and estimate CVP using ultrasound. One of the ultrasonographic (US) technique for obtaining the JVP from a high-resolution B-mode sonogram sequences (US-JVP), recording the changes in IJV-CSA (cross section area) over the cardiac cycle (CC) has been proposed which appears to have potential as an approach for estimating CVP. Patients and Methods: It is a prospective double blinded observational study conducted at tertiary hospital among 40 consenting patients. Results: We found that 27 patients (67.5%) had correct prediction of CVP by USG with measured CVP after transducing central venous catheter at baseline (supine position). Similarly, 19 patients (47.5%) had correct prediction of CVP with measured CVP after passive leg raising. We found that 14 patients (35%) had 10% rise in mean arterial pressure on passive leg raising. We denoted these patients as Responders. We found that both responders and non-responders had poor correlation with CVP prediction. Also IVC diameters and collapsibility index did not predict the fluid responsiveness of the patients. Spearman correlation coefficient was used to study correlation between two quantitative variables. In our study, we found a strong positive correlation between predicted CVP (determined by USG parameters) and measured CVP (determined by transducing central venous catheter on monitor) at baseline (supine position) and after passive leg raising. Multivariate regression analysis was done to find the significant predictor of CVP which was found to be IVC maximum diameter (p value 0.01) determined by USG. Conclusion: Bedside USG in preoperative patients can be used as a simple and reliable method to calculate IVC diameters and collapsibility index to predict CVP. It requires minimal training and correlates well with real time transduced CVP. In our study of 40 patients we aimed to study the ability of the ultrasound guided measurements of the Inferior Vena Cava in predicting the Central Venous Pressure (CVP). A strong positive correlation was found between the predicted CVP and measured/transduced CVP in supine position 8 (baseline) and after passive leg raising. On multivariate regression analysis, the IVC maximum diameter determined by USG was found to be the significant predictor of CVP. No significant correlation was noted between IVC parameters, Collapsibility index and CVP values to predict fluid responsive nature of the patients.