Abstract
Edema and infection represent serious complications of blunt extremity trauma. It is important to differentiate between pathophysiological changes within tissues proximal and within distal to the site of trauma. The aim was to investigate the effects of soft tissue trauma on the microcirculation of the mouse lower limb. Endothelial leakage and leukocyte accumulation proximal and distal to the site of trauma were studied using intravital fluorescence microscopy.
Low-energy trauma to the lower limb was defined in previous experiments as a trauma transferring 50% of the energy required to produce tibial fracture. The trauma was inflicted under general anesthesia by an accelerator, hitting the mid-section of the calf in a perpendicular direction. 5, 90, and 180 minutes after trauma, the following microcirculatory parameters were measured: diameter of arterioles, venules, functional capillary density (FCD), extravasation of FITC-dextrane, and leukocyte-endothelial cell-interactions. Two groups (control and trauma) were studied proximal to, distal to and at the site of trauma. Skin, subcutaneous tissue and muscle were investigated individually in the trauma and the control groups (each group n=7).
At the site of trauma, distinct extravasation and edema formation in all tissues was observed. In subcutaneous and muscle tissue, microvascular thrombosis as well as edema were detected proximal and distal to the trauma. FCD was reduced in muscle and fat tissue. The numbers of rolling and adherent leukocytes were enhanced 5 minutes after trauma and throughout the observational period.
Our results demonstrate endothelial leakage and extravasation early after low-energy soft tissue trauma in all soft tissues proximal and distal to the site of trauma. In addition, we found high accumulation of leukocytes in all locations, especially in soft tissues. The model presented is ideally suited for the in vivo investigation of new therapeutic strategies for edema and thrombosis prevention in animals with soft tissue trauma.
