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 in jury remains high despite a decrease in mortality rate, Several theori es 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 ti ssue response after electrical injury remains incompletely understood with nothing new to offer these unfortunate patients. We have develope d a rat gracilis muscle intravital microscopy preparation in order to better under stand the mechanisms of this injury. A standardized 40-V stimulation of 10-sec duration was applied to the anterior belly of th e gracilis muscle which translated into a current load of 30 mA. The c urrent density was 750 mA/cm(2). Sequential intravital assessment of m icrocirculatory changes before injury, as well as 5, 15, 30, 60, 120, 180 and 240 min after injury was performed, Consistent findings includ ed initial cessation of blood flow in many capillary beds, focal flow reversal, venous and arterial vascular spasm. Restitution of microvasc ular flow varied from several minutes to 1 hr and was preceded by vaso dilation at 5-15 min following the injury (+16.9 mu m from baseline at 15 min). Starting at 30 min progressive vasoconstriction was noted (- 0.8 mu m from baseline at 30 min, -31.3 mu m from baseline at 4 hr). H igh resolution observation of neutrophil behavior showed an increase i n the number of these cells adherent to venular endothelium in areas e xhibiting circulatory disturbances (+11.4 cells at 5 min, + 15 cells a t 4 hr). The standardization of this model allows a quantitative metho d of evaluating the microcirculatory changes associated with electrica l injury and of studying ways to prevent tissue damage. The microcircu latory changes induced by electrical injury were similar to those repo rted in ischemia-reperfusion injury of skeletal muscle. (C) 1995 Acade mic Press, Inc.