Evaluation of Mesenteric Microvascular Hyperpermeability Following Hemorrhagic Shock Using Intravital Microscopy.

Intravital microscopy is a powerful tool for evaluating vascular hyperpermeability in various vascular beds. Hemorrhagic shock after traumatic injury is known to induce microvascular hyperpermeability, life-threatening edema, and microcirculatory perfusion disturbances. Here we describe the microsurgical and imaging methods to study mesenteric vascular hyperpermeability using intravital microscopy, in a rat model of hemorrhagic shock. In this protocol, hemorrhagic shock is induced by controlled withdrawal of blood to reduce the mean arterial pressure (MAP) to 40 mmHg for 60 min, followed by resuscitation for 60 min. To study the changes in vascular permeability, the rats are given FITC-albumin, a fluorescent tracer, intravenously. The FITC-albumin flux across the vessel wall is measured in mesenteric postcapillary venules by determining intravascular and extravascular fluorescence intensity under intravital microscopy. Intravital microscopic evaluation of high molecular weight FITC-albumin permeability is a reliable indicator of microvascular hyperpermeability.