Acute renal failure complicating muscle crush injury

Extensive skeletal muscle injury, whether caused by mechanical crush or by extreme physical exertion, is incompatible with life, unless treated early and vigorously. The immediate cause of morbidity is leakiness of the sarcolemmal membrane to cardiotoxic or nephrotoxic cations and metabolites (K, PO4, myoglobin and urate) of the sarcoplasma, and rapid massive uptake by the muscles of extracellular fluid, sodium and calcium, leading to profound hypovolemic and hyocalcemic shock. Casualties who survive the early steep of hyperkalemia and arterial hypotension are susceptible to myoglubinuric acute renal failure owing mainly to the combination of renal vasoconstriction, nephrotoxicity, and tubular obstruction by myoglobin plugs and urate. Management includes immediate (prehospital) intravenous volume replacement followed by mannitol-alkaline diuresis. The alkali regimen ameliorates the acidosis associated with shock and the hyperkalemia, and protects against the nephrotoxicity of myoglobin and urate by alkalinization of the urine. Mannitol, through its impermeant hyperoncotic properties, decompresses and mobilizes muscle edema and promotes renal tubular flow, thus flushing myoglobin plugs and enhancing urinary elimination of nephrotoxic metabolites. With this regimen and when necessary also with the use of dialysis, a substantial salvage of lives, limbs, and kidney function has been achieved recently compared with invariable mortality for casualties who were buried for 3 to 4 hours or more in the early 1940s (World War 2).