Rhabdomyolysis: The Daily PANCE Blueprint
A 21-year-old football player collapses during the first outdoor practice of the season and is brought to the emergency department with severe diffuse muscle pain and weakness. He is producing small volumes of dark, tea-colored urine. The urine dipstick is strongly positive for blood, but microscopy shows no red blood cells. Laboratory studies show a creatine kinase of 42,000 U/L, potassium 5.3 mEq/L, calcium 7.9 mg/dL, phosphate 5.4 mg/dL, and a creatinine of 2.6 mg/dL. His ECG shows no peaked T waves and no QRS widening, and he is passing urine. Which of the following is the most appropriate initial step in management?
A. Aggressive intravenous isotonic crystalloid
B. Intravenous sodium bicarbonate to alkalinize the urine
C. Intravenous mannitol
D. Intravenous furosemide
E. Urgent hemodialysis
Answer and topic summary
The answer is A. Aggressive intravenous isotonic crystalloid
Early, aggressive intravenous isotonic crystalloid is the single intervention that changes outcome in rhabdomyolysis, and nothing else comes close. Myoglobin released from crushed muscle is directly toxic to tubular cells, precipitates as casts that obstruct the tubules, and causes renal vasoconstriction — and all three of those mechanisms are worsened by hypovolemia, because injured muscle sequesters enormous volumes of fluid. Start normal saline at a high rate, commonly 200 to 1,500 mL/hour depending on severity, and titrate to a urine output of roughly 3 mL/kg/hour (about 200–300 mL/hour in an adult). After the first few liters, many clinicians switch to a balanced crystalloid such as lactated Ringer’s to avoid a hyperchloremic acidosis. Continue fluids until the CK falls below about 1,000 U/L, and recheck potassium, calcium, phosphate, and creatinine serially. His labs are classic: a CK of 42,000, a dipstick positive for blood with no red cells on microscopy (the dipstick cannot tell myoglobin from hemoglobin), hyperkalemia and hyperphosphatemia from lysed muscle, and hypocalcemia as calcium deposits in damaged tissue. Sorting the distractors: sodium bicarbonate is theoretically attractive — alkaline urine should keep myoglobin from precipitating — but there is no clear evidence that alkaline diuresis beats saline diuresis at preventing acute kidney injury, and it risks worsening the hypocalcemia; reserve it for significant acidosis or hyperkalemia. Mannitol is not routinely recommended and should never be given before the tank is full or to an oliguric patient. Furosemide treats volume overload; giving a diuretic to a volume-depleted patient makes the kidney injury worse. And hemodialysis is for the patient who has already declared himself — refractory hyperkalemia, uncorrectable acidosis, uremia, anuria, or fluid overload — none of which describes a young man with a potassium of 5.3, a clean ECG, and urine still coming out.
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