The collapsed inferior vena cava (IVC) in computed tomography (CT) images can be found in patients with hypovolemic shock, making it an attractive diagnostic sign in early treatment of trauma patients. However, current research results are controversial.

To examine the dimensional change of IVC during acute hemorrhage through a volume controlled acute hemorrhagic shock model in swine.

Volume controlled hemorrhage was performed in 10 adult Bama minipigs. Enhanced CT scan and hemodynamic monitoring were performed when the cumulative blood loss volume reached 0%, 10%, 20%, 30%, and 40%. The transverse diameter (T) and anteroposterior diameter (AP) of IVC were measured in axial images. Hemodynamic parameters were obtained with a Pulse Contour Cardiac Output (PiCCO) hemodynamic monitor device. Arterial blood samples were also collected for artery blood gas analysis at each time point.

As the blood loss volume increased, the collapsibility (T/AP) and cross section area (CSA) of IVC significantly changed in hepatic level and pre-renal level. The significant decrease of the CSA of IVC (shrink) occurred early when the blood loss volume reached only 10%.

The IVC shrank early but collapsed late during acute hemorrhages in swine. The collapsed IVC on CT scans suggested a severe hypovolemic shock state but not an early indicator for shock.