Agreement between subcostal and transhepatic longitudinal imaging of the inferior vena cava for the evaluation of fluid responsiveness: A systematic review

Assessment of fluid-responsiveness is a key aspect of daily management in critically ill patients. Non-invasive evaluation of the variation of inferior vena cava (IVC) diameter during ventilation may provide useful information. However, a standard sagittal IVC visualization from the subcostal (SC) region is not always feasible. An alternative method to visualize the IVC is a coronal trans-hepatic (TH) approach. We performed a systematic search to explore the interchangeability of IVC evaluation with SC and TH views. We searched Medline and EMBASE to identify prospective studies. We did not consider the relationship between axial and sagittal visualization of the IVC. We included seven studies reporting data on IVC evaluation with both SC and TH IVC views. Four studies were conducted on spontaneously breathing patients/volunteers, two on fully mechanically ventilated patients, and one in a mixed population, with large heterogeneity regarding the analyses reported. Limits of agreement between SC and TH were large. Concordance of the IVC collapsibility/distensibility indices are not interchangeable between SC and TH view. Correlation between diameters measured with SC and TH approach and intra/inter-observer correlation produced variable results. An overview of the included studies suggests that longitudinal TH and SC assessment of IVC size and respiratory variation are not interchangeable. New studies with accurate data reporting and appropriate statistical analysis are needed to define proper cut-offs for fluid responsiveness when using TH approach for IVC visualization.