A model for recording the microcirculatory changes associated with standardized electrical injury of skeletal muscle

The rate of major limb amputation following high voltage electrical injury remains high despite a decrease in mortality rate. Several theories about the pathophysiology of electrical injury have been discussed in the literature and different clinical regimens have been attempted to decrease the high amputation rate. However, to date, the overall tissue response after electrical injury remains incompletely understood with nothing new to offer these unfortunate patients. We have developed a rat gracilis muscle intravital microscopy preparation in order to better understand the mechanisms of this injury. A standardized 40-V stimulation of 10-sec duration was applied to the anterior belly of the gracilis muscle which translated into a current load of 30 mA. The current density was 750 mA/cm2. Sequential intravital assessment of microcirculatory changes before injury, as well as 5, 15, 30, 60, 120, 180 and 240 min after injury was performed. Consistent findings included initial cessation of blood flow in many capillary beds, focal flow reversal, venous and arterial vascular spasm. Restitution of microvascular flow varied from several minutes to 1 hr and was preceded by vasodilation at 5-15 min following the injury (+16.9 microns from baseline at 15 min). Starting at 30 min progressive vasoconstriction was noted (-0.8 micron from baseline at 30 min, -31.3 microns from baseline at 4 hr). High resolution observation of neutrophil behavior showed an increase in the number of these cells adherent to venular endothelium in areas exhibiting circulatory disturbances (+11.4 cells at 5 min, +15 cells at 4 hr). The standardization of this model allows a quantitative method of evaluating the microcirculatory changes associated with electrical injury and of studying ways to prevent tissue damage. The microcirculatory changes induced by electrical injury were similar to those reported in ischemia-reperfusion injury of skeletal muscle.