Critical Care Scenarios
Episode 25: Rhabdomyolysis
Initial workup, fluid management, renal replacement, and other subtleties of caring for the critically ill patient with rhabdomyolysis.
* Rhabdomyolysis is defined by elevated levels of creatinine kinase and/or myoglobin in the serum secondary to skeletal muscle breakdown with release of cellular contents. Common causes are crush or compartment syndrome, prolonged downtime on hard ground in patients who fell and cannot stand back up, and a variety of less common phenomena.* Monitor with serum CK and/or myoglobin every 4–12 hours. Urine myoglobin is usually elevated, and AST/ALT, troponin, LDH, and potassium are all commonly high as well.* The mainstay of treatment is vigorous hydration to flush the kidneys and prevent nephrotoxicity from myoglobin precipitation in the tubules. Historically this was via sodium bicarbonate (as myoglobin is less likely to precipitate in an alkaline environment) and forced diuresis with mannitol. These can be considered, but isotonic crystalloid may be as good in most cases.* Do consider bicarb in the most severe cases, particularly if renal failure seems incipient. Maybe consider diuresis if the urine output is poor and fluid balance is increasingly positive. If oliguric due to AKI, consider reducing fluids, as the goal is urine output, not hypervolemia.* Consider trending CK until it peaks, which may require dilution by the lab if it exceeds the upper limit of their assay. A CK that continues to rise may indicate an ongoing source of muscle injury. Consider trending urine pH as well if alkalinizing the urine with bicarb, targeting a pH >6.5.* The lion’s share of rhabdo is mild or moderate, and often an incidental finding in the setting of other illness or injury. Occasional cases are severe and high risk for renal failure. The McMahon score can be used to try and predict these cases.* In general, the role of hemodialysis or CVVH is the same as for anyone: renal replacement if kidney injury progresses to the point where it’s indicated. Some experimental work is underway with super high-flux CVVH filters which may help clear myoglobin, but in general CRRT has no disease-specific effects on rhabdo.