What are the symptoms and management of rhabdomyolysis?

Rhabdomyolysis: Clinical Presentation and Management

Rhabdomyolysis presents classically with the triad of muscle pain, weakness, and dark (tea-colored or reddish-brown) urine, though this complete triad is often absent. 1, 2

Clinical Symptoms

Cardinal Features

• Muscle pain (myalgia), particularly in proximal muscles of the upper and lower extremities 1, 2, 3
• Muscle weakness, especially affecting proximal muscle groups 4, 2, 5
• Dark urine (red-to-brown color) due to myoglobinuria, which should immediately raise suspicion for rhabdomyolysis 1, 2, 3

Additional Symptoms

• Muscle tenderness and swelling in affected muscle groups 6
• Severe fatigue that may accompany muscle symptoms 4
• Muscle stiffness and cramping in statin-associated cases 4

Important Clinical Caveat

Many patients present with asymptomatic elevation of muscle enzymes without the classic triad, representing a spectrum from mild to fulminant disease 1, 5. Dark urine is a late finding and its absence does not exclude rhabdomyolysis 3.

Diagnostic Evaluation

Laboratory Confirmation

• Creatine kinase (CK) elevation ≥10 times the upper limit of normal is the biochemical gold standard for diagnosis 1, 5
• Myoglobin is the gold standard for prognostication, particularly in non-traumatic cases 1
• Urinalysis showing brown color, cloudiness, and positive for blood without RBCs (indicating myoglobinuria) 4, 3

Essential Laboratory Monitoring

• Serum creatinine to assess for acute kidney injury 4, 7
• Electrolytes, particularly potassium, as hyperkalemia can cause life-threatening cardiac arrhythmias 7, 5
• Calcium, phosphorus, and magnesium levels 7
• Liver function tests (AST and ALT are often elevated) 7, 3
• Coagulation studies to evaluate for disseminated intravascular coagulation in severe cases 7

Compartment Syndrome Surveillance

• Early signs: Pain, tension, paresthesia, and paresis 7
• Late signs: Pulselessness and pallor (indicating irreversible damage) 7
• Compartment pressure monitoring: Consider fasciotomy when pressure exceeds 30 mmHg or when differential pressure (diastolic BP - compartment pressure) is <30 mmHg 7

Acute Management

Immediate Interventions

Discontinue the offending agent immediately if statin-induced or drug-related rhabdomyolysis is suspected 4

Fluid Resuscitation (Critical Priority)

• Early initiation of aggressive intravenous saline is the cornerstone of treatment, as delayed treatment increases acute kidney injury risk 7, 5
• Target urine output ≥300 mL/hour 5
• Severe rhabdomyolysis (CK >15,000 IU/L): May require >6L of fluid resuscitation 7
• Moderate cases: Typically 3-6L per day 7

Adjunctive Therapies

• Sodium bicarbonate for patients with metabolic acidosis 7, 5
• Mannitol if urine output goals are not met with saline alone 5

Electrolyte Management

• Monitor and correct hyperkalemia aggressively to prevent cardiac arrhythmias and arrest 7, 5
• Serial electrolyte measurements throughout treatment 7

Surgical Intervention

• Early fasciotomy is indicated for established compartment syndrome 7

Duration of Treatment

• Continue IV fluids until CK levels decrease to <1,000 U/L 5

Risk Factors to Identify

Common Causes

• Trauma, especially crush injuries and severe limb trauma 7
• Exertional causes, particularly novel overexertion or unaccustomed exercise volume/intensity 7, 3, 6
• Medications, particularly statins (incidence 1.6 per 100,000 patient-years), with increased risk from drug interactions like gemfibrozil 4, 7
• Genetic factors: SLCO1B1 gene mutations increase statin-induced rhabdomyolysis risk 4

Patient-Specific Risk Factors

• Age, diabetes, renal impairment, cardiovascular disease 4

Critical Complications

Life-Threatening Sequelae

• Acute kidney injury (occurs in 13-50% of cases, the most significant complication) 1, 5
• Severe hyperkalemia leading to cardiac arrhythmias 7, 5
• Compartment syndrome (can develop early or late) 7, 5
• Disseminated intravascular coagulation 7, 5
• Metabolic acidosis 7

Delayed Complications

• Myonecrosis with calcium overload causing myocyte death 4
• Myoglobinuric renal failure requiring dialysis 4, 5

Special Considerations

Perioperative Management

• Avoid succinylcholine in patients with suspected or confirmed rhabdomyolysis 7
• Maintain adequate hydration throughout the perioperative period 7

Statin-Associated Cases

When severe muscle symptoms or rhabdomyolysis occur with statins, promptly discontinue the statin and evaluate CK, creatinine, and urinalysis for myoglobinuria 4. Consider nonstatin therapies (ezetimibe, PCSK9 inhibitors, bempedoic acid) for patients requiring continued lipid management 4.