Diagnostic accuracy of subclavian vein collapsibility index versus inferior vena cava collapsibility index for predicting post induction hypotension: An observational study.

Ultrasound (US) guided measurement of inferior vena cava (IVC) diameter and it’s respiratory variability i.e collapsibility index (CI) has been shown to predict the post induction hypotension with high sensitivity and specificity. However, in conditions like pregnancy, abdominal distension, obesity etc it is difficult to scan the IVC and to assess the volume status. The role of US guided measurements of other central veins like internal jugular vein, femoral vein etc in predicting the volume status were also evaluated. The diagnostic accuracy for them was found to be inferior to the IVC. Recently, the sub clavian vein (SCV) CI  during deep inspiration was shown to predict the post induction hypotension. In the available literature there is no head to head comparison of IVC and SCV for prediction of post induction hypotension. Therefore in our study we will compare the diagnostic accuracy of US guided measurement of IVC and SCV parameters during quiet and deep breathing for predicting post induction hypotension. We hypothesize that there will be no difference between the diagnostic accuracy of SCV- CI and IVC-CI for prediction of post induction hypotension.