What are the laboratory findings, clinical features, and management of rhabdomyolysis (a condition characterized by the breakdown of skeletal muscle tissue)?

From the Guidelines

Rhabdomyolysis is a serious condition that requires immediate attention, and management should focus on aggressive intravenous fluid resuscitation with normal saline at 200-300 mL/hour initially, aiming for urine output of 200-300 mL/hour until CK levels decrease significantly, as recommended by recent guidelines 1.

Lab Findings

Lab findings for rhabdomyolysis include:

• Markedly elevated creatine kinase (CK) levels typically >5,000 U/L and often >10,000 U/L
• Elevated serum myoglobin
• Hyperkalemia, hyperphosphatemia, hypocalcemia
• Elevated liver enzymes, and elevated blood urea nitrogen and creatinine
• Urinalysis shows myoglobinuria with tea-colored or cola-colored urine that tests positive for blood on dipstick but has few or no red blood cells on microscopy, as noted in studies 1

Clinical Features

Clinical features of rhabdomyolysis include:

• Muscle pain, weakness, and swelling, particularly in the shoulders, thighs, and lower back
• Patients may present with fever, malaise, nausea, vomiting, and altered mental status
• Raising CPK levels above five times normal (approximately 1000 IU/L) is a sign of rhabdomyolysis, and levels above 75,000 IU/L are associated with a high incidence of newly formed acute kidney injury 1

Management

Management of rhabdomyolysis should prioritize:

• Aggressive intravenous fluid resuscitation with normal saline at 200-300 mL/hour initially, aiming for urine output of 200-300 mL/hour until CK levels decrease significantly
• Urinary alkalinization with sodium bicarbonate (150 mEq/L in D5W) may be considered if urine pH is <6.5, though this remains controversial 1
• Electrolyte abnormalities should be corrected, particularly hyperkalemia which may require calcium gluconate, insulin with glucose, sodium bicarbonate, or potassium-binding resins
• Renal replacement therapy is indicated for severe acute kidney injury, refractory hyperkalemia, or severe acidosis
• The underlying cause of rhabdomyolysis should be identified and treated, and CK levels should be monitored daily until declining, and fluid status and electrolytes require close monitoring to prevent complications, as suggested by recent studies 1

From the Research

Lab Findings

• Elevated creatine kinase levels are used to confirm the diagnosis of rhabdomyolysis 2
• Myoglobinuria is a key feature of rhabdomyolysis, with myoglobin being the primary muscle constituent contributing to renal damage 2
• Electrolyte abnormalities, such as hyperkalemia, are common in rhabdomyolysis 2, 3

Clinical Features

• Rhabdomyolysis is a clinical syndrome of muscle injury associated with myoglobinuria, electrolyte abnormalities, and often acute kidney injury (AKI) 2
• Common causes of rhabdomyolysis include prescription and over-the-counter medications, alcohol, and illicit drugs 2
• Complications of rhabdomyolysis include acute renal failure, hyperkalemia, and compartment syndrome 2, 3

Management

• Early and aggressive fluid resuscitation is the main intervention for preventing and treating AKI in rhabdomyolysis 4, 2, 3
• Automated fluid management has been shown to optimize urine output and prevent fluid accumulation in rhabdomyolysis patients 5
• The use of bicarbonate-containing fluids, mannitol, and loop diuretics is not supported by high-quality evidence 4, 2
• Dialytic treatment may be necessary to correct hydroelectrolytic imbalance and renal function alterations in patients with rhabdomyolysis-induced acute renal failure 6
• Early vigorous fluid resuscitation with ≥12 l daily intravenous infusion of alkaline solution has been shown to reduce mortality in patients with rhabdomyolysis caused by muscle crush syndrome 3