What is the workup for rhabdomyolysis?

Workup for Rhabdomyolysis

The workup for rhabdomyolysis should include serum creatine kinase (CK) measurement, complete electrolyte panel, renal function tests, urinalysis, and assessment for compartment syndrome to guide management and prevent complications. 1

Initial Laboratory Assessment

• Serum creatine kinase (CK) measurement is the cornerstone of diagnosis, with levels typically at least 10 times the upper limit of normal (>15,000 IU/L in severe cases) 1, 2
• Complete electrolyte panel, with particular attention to potassium, calcium, phosphorus, and magnesium levels, as hyperkalemia can lead to life-threatening cardiac arrhythmias 1, 3
• Renal function tests including BUN and creatinine to assess for acute kidney injury 1, 2
• Urinalysis to detect myoglobinuria (appears as red-to-brown urine) 4, 2
• Arterial blood gas analysis to assess for metabolic acidosis in severe cases 1
• Liver function tests to evaluate for hepatic involvement 1
• Coagulation studies to rule out disseminated intravascular coagulation as a complication 1, 3

Etiology-Specific Testing

• Medication review to identify potential causative agents, particularly statins, which can cause rhabdomyolysis through drug interactions 1, 5
• Assessment for trauma or crush injuries, which are common causes of rhabdomyolysis 1
• Evaluation for exertional causes, particularly novel overexertion or unaccustomed exercise 1
• Viral studies if viral myositis is suspected 1
• Autoimmune markers (ANA, ASMA, ANCA) if autoimmune myopathy is suspected 1
• Toxicology screening if drug or toxin exposure is suspected 4

Clinical Assessment

• Evaluation for early signs of compartment syndrome, including pain, tension, paresthesia, and paresis 1
• Monitoring for late signs of compartment syndrome, including pulselessness and pallor, which often indicate irreversible damage 1
• Measurement of compartment pressures when clinically indicated (consider fasciotomy when compartment pressure exceeds 30 mmHg) 1, 6
• Cardiac assessment, including ECG and cardiac troponin, to rule out cardiac involvement and monitor for arrhythmias due to electrolyte abnormalities 1, 6

Monitoring During Treatment

• Serial CK measurements to track muscle breakdown and response to treatment 1, 2
• Repeated electrolyte measurements, particularly potassium, to monitor for life-threatening hyperkalemia 1, 5
• Urine output monitoring with a goal of at least 300 mL/hour to prevent acute kidney injury 6, 2
• Continuous assessment of renal function to detect acute kidney injury early 1, 7

Common Pitfalls and Caveats

• Delayed recognition of rhabdomyolysis can lead to preventable acute kidney injury; maintain a high index of suspicion in high-risk scenarios (intoxication, prolonged immobilization, altered mental status) 8, 2
• Failure to monitor for compartment syndrome can result in limb-threatening complications requiring fasciotomy 1, 6
• Inadequate fluid resuscitation is associated with higher risk of acute kidney injury; early and aggressive IV fluid therapy is critical 1, 7
• Overlooking drug interactions that can precipitate rhabdomyolysis, particularly with statins and certain antibiotics like macrolides 5
• Neglecting to evaluate for underlying metabolic, endocrine, or genetic disorders that may predispose to recurrent episodes of rhabdomyolysis 4