What are the laboratory findings and management of rhabdomyolysis (muscle breakdown disease)?

From the Guidelines

Rhabdomyolysis should be managed with aggressive intravenous fluid resuscitation, monitoring of serum electrolytes and renal function, and prompt treatment of hyperkalemia and metabolic acidosis to prevent acute kidney injury and cardiac arrhythmias. The diagnosis of rhabdomyolysis is primarily based on elevated serum creatine kinase (CK) levels, typically greater than 5 times the upper limit of normal (>1,000 U/L), often reaching tens of thousands 1. Management centers on aggressive intravenous fluid resuscitation with normal saline at 1-2 L/hour initially, then adjusted to maintain urine output of 200-300 mL/hour until CK levels decrease significantly.

Key Management Strategies

• Monitoring should include serum electrolytes (particularly potassium, calcium, and phosphorus), renal function tests, and urine myoglobin 1.
• Hyperkalemia should be treated promptly with calcium gluconate, insulin with glucose, sodium bicarbonate, or potassium-binding resins depending on severity.
• Metabolic acidosis may require sodium bicarbonate administration (150 mEq in 1L D5W) if pH falls below 7.2.
• Hypocalcemia should only be treated if symptomatic or severely low.
• Discontinue any causative medications or substances and address the underlying cause (trauma, seizures, infections, etc.).
• Renal replacement therapy may be necessary for patients with severe acute kidney injury, persistent hyperkalemia, or severe acidosis.
• Compartment syndrome should be evaluated in limb-involved cases, potentially requiring fasciotomy, with clinical signs including pain, tension, paraesthesia, paresis, and increased compartmental pressure monitoring 1.

Laboratory Monitoring

• CK levels should be monitored daily until trending downward, with continued IV fluids until CK falls below 1,000 U/L.
• Point-of-care devices such as iStat can be used to monitor electrolytes, acid-base status, lactate, creatine kinase, blood urea nitrogen, and creatinine levels in the field, especially when standard laboratory infrastructure is not available 1.

From the Research

Lab Findings in Rhabdomyolysis

• Elevated serum creatine kinase (CK) level, typically > 1000 U/L or at least 5x the upper limit of normal 2
• Presence of myoglobinuria, as indicated by urinalysis 2
• Elevated serum myoglobin levels 2
• Full metabolic panel, including serum creatinine and electrolytes, to assess for acute kidney injury (AKI) and electrolyte imbalances 2

Management of Rhabdomyolysis

• Early and aggressive fluid replacement using crystalloid solution to prevent and treat AKI 2, 3
• Treatment of the underlying cause of the muscle insult 2
• Electrolyte imbalances should be treated with standard medical management 2
• No established benefit of using mannitol or giving bicarbonate infusion, except to correct systemic acidosis 4, 2, 5
• Automated fluid management may optimize urine output and prevent AKI 6

Key Recommendations

• Aggressive intravenous fluid resuscitation (IVFR) is conditionally recommended to improve outcomes of acute renal failure (ARF) and lessen the need for dialysis 4
• IVFR should be initiated as soon as possible, preferably within the first 6 hours after muscle injury, at a rate that maintains a urine output in adults of 300 mL/h or more for at least the first 24 hours 5
• Sodium bicarbonate and mannitol should be used judiciously, only if necessary to correct systemic acidosis or maintain urine output 4, 5