Measurement of Internal Jugular Vein and Common Carotid Artery Diameter Ratio by Ultrasound to Estimate Central Venous Pressure

: Objective The objective of this study is to find a correlation between internal jugular vein (IJV) and common carotid artery (CCA) diameter ratio and central venous pressure (CVP) measurement and find a cut-off value for the IJV/CCA ratio to predict low CVP i.e. < 10 cm H20, for estimating the volume status in critically ill patients. Methods This prospective cross-sectional study was conducted at the critical care department of Shifa International Hospital, Islamabad, from July to December 2017. A sample of 49 patients ≥ 18 years with intrathoracic central venous catheters (CVCs) who underwent bedside sonographic assessments of IJV and CCA diameter were included in this study using convenient sampling. The IJV/CCA diameter ratio was calculated and correlated with CVP and the predictive value of the IJV/CCA diameter ratio to predict CVP < 10 cm H2O was explored by calculating the area under the receiver operating characteristic (ROC) curve, sensitivity, specificity, and positive and negative predictive values. Results A total of 49 patients, 30 males (61.2%) and 19 females (38.8%) with a mean age of 56.00±16.11 years were included in the study. The mean CVP was 8.98±2.37cm H2O in ventilated (51%) and 10.7± 6.01 cm H2O in non-ventilated (49%) patients. The mean IJV/CCA diameter ratio was 1.60±0.55 at expiration and 1.41±0.56 at inspiration. There was a significant correlation between the IJV/CCA diameter ratio and CVP at expiration (r=0.401, p=0.004). The correlation between IJV/CCA and CVP was significant in non-ventilated patients at expiration (r=0.439, p=0.032). The area under the ROC curve for the IJV/CCA diameter ratio for predicting CVP < 10 cm H2O was 0.684 (p=0.028). The predictive value of the IJV/CCA diameter ratio for CVP < 10 cm H20 at the cutoff value of < 2 was insignificant. A new cut-off < 1.75 was taken for the IJV/CCA diameter ratio from the coordinates of the ROC curve. The sensitivity, specificity, PPV, and NPV of an IJV/CCA diameter ratio of < 1.75 for predicting a CVP < 10 cm H20 were 84.62%, 52.17%, 66.67%, and 75.00%, respectively. Conclusion The assessment of volume status by the IJV/CCA diameter ratio with a sonographic device may be a useful noninvasive alternative for a central venous catheterization with a cut-off < 1.75.