What is the management approach for a patient with suspected rhabdomyolysis?

Management of Rhabdomyolysis

Immediately initiate aggressive intravenous fluid resuscitation with isotonic saline targeting a urine output of 300 mL/hour, discontinue all causative agents, and monitor potassium levels every 6-12 hours to prevent life-threatening cardiac arrhythmias. 1

Immediate Diagnostic Workup

Upon suspicion of rhabdomyolysis, obtain the following laboratory tests immediately:

• Creatine kinase (CK) - diagnosis is established when CK is ≥5-10 times the upper limit of normal (≥975-1000 IU/L) 2, 1
• Comprehensive metabolic panel including creatinine, BUN, electrolytes (particularly potassium), glucose, calcium, and phosphorus 2
• Urinalysis for myoglobinuria - look for brown/dark urine that is positive for blood without red blood cells present 2
• ECG immediately to assess for arrhythmias related to hyperkalemia 2
• Arterial blood gas to assess for metabolic acidosis, which commonly occurs in severe cases 2
• Complete blood count with differential to evaluate for infection or systemic processes 2

Additional muscle enzymes including LDH, AST, ALT, and aldolase should be measured as they are commonly elevated 3

Severity Stratification

Classify the severity to guide fluid resuscitation volume:

• Mild: CK <15,000 IU/L with normal renal function and no significant electrolyte abnormalities 2
• Moderate: CK 15,000-50,000 IU/L with mild renal dysfunction, requiring 3-6L fluid resuscitation per day 3, 2
• Severe: CK >50,000 IU/L with acute kidney injury, requiring >6L fluid resuscitation per day and high risk for complications 3, 2

Aggressive Fluid Resuscitation Protocol

This is the cornerstone of management and delays are associated with dramatically higher acute kidney injury risk 3, 1:

• Initiate isotonic saline (0.9% NaCl) immediately upon diagnosis 1
• Target urine output of 300 mL/hour to facilitate myoglobin clearance and prevent renal tubular obstruction 3, 1, 4
• Fluid volume requirements based on severity: severe cases (CK >15,000 IU/L) require >6L per day; moderate cases require 3-6L per day 3, 1
• Continue IV fluids until CK <1,000 U/L 2
• Monitor urine output hourly to ensure adequate clearance 2

For trauma patients, use isotonic saline and avoid hypotonic solutions such as Ringer's lactate if there is any concern for head trauma 3

Critical Electrolyte Management

Hyperkalemia represents the most immediately life-threatening complication, capable of precipitating cardiac arrhythmias, pulseless electrical activity, and cardiac arrest 1:

• Check potassium levels every 6-12 hours in severe cases 2, 1
• Correct significant hyperkalemia emergently with standard protocols 1
• Monitor calcium, phosphorus, and magnesium for hypocalcemia and hyperphosphatemia 2
• Trend CK, creatinine, and electrolytes daily until CK is declining and renal function is stable 3

Immediate Medication Review and Discontinuation

Discontinue all causative agents immediately 3, 1:

• Statins and other lipid-lowering agents - particularly simvastatin 80 mg which carries higher risk 3
• Dietary supplements: red yeast rice containing lovastatin, creatine monohydrate, wormwood oil, licorice, and Hydroxycut 3
• NSAIDs - avoid entirely due to nephrotoxic effects 1
• Succinylcholine in perioperative settings 3, 1
• All over-the-counter medications and herbal supplements that may contribute 3

Compartment Syndrome Surveillance

Maintain extremely high suspicion for compartment syndrome, which can both cause and complicate rhabdomyolysis 3, 1:

• Early signs: pain, tension, paresthesia, and paresis 3
• Late signs: pulselessness and pallor (often indicate irreversible damage) 3
• Perform early fasciotomy when compartment pressure exceeds 30 mmHg or when differential pressure (diastolic BP minus compartment pressure) is <30 mmHg 3, 1

Pain Management Strategy

Use a stepwise approach that avoids nephrotoxic agents:

• First-line: Acetaminophen 500-1000 mg with onset in 15-30 minutes, maximum daily dose 4-6 grams 3, 1
• Avoid all NSAIDs (ibuprofen, ketoprofen, diclofenac, naproxen, mefenamic acid) due to gastrointestinal and renal toxicity 3
• For severe pain unresponsive to acetaminophen: oral morphine 20-40 mg for opioid-naive patients 3
• If acute kidney injury with eGFR <30 ml/min: use fentanyl or buprenorphine as safest opioid choices 3

Serial Monitoring Protocol

Establish systematic surveillance throughout treatment:

• Hourly urine output monitoring targeting ≥300 mL/hour 2, 1
• Daily CK levels until declining 2
• Electrolytes every 6-12 hours in severe cases, particularly potassium 2
• Daily renal function (creatinine and BUN) until stable 2
• Cardiac troponin in severe cases to rule out cardiac involvement 2

Renal Replacement Therapy Indications

Consider dialysis for specific complications rather than prophylactically 1:

• Refractory hyperkalemia unresponsive to medical management
• Severe metabolic acidosis
• Progressive acute kidney injury despite adequate hydration
• Persistently elevated CK despite adequate fluid resuscitation

Etiology-Specific Considerations

For recurrent episodes or unclear etiology, consider additional workup:

• Genetic testing: RYR1 and CACNA1S gene sequencing for malignant hyperthermia susceptibility, particularly with exertional rhabdomyolysis or heat illness 3
• Metabolic myopathy testing: CPT2, PYGM, ACADM, AMPD1, and VLCAD gene testing for recurrent cases 3
• Autoimmune markers: ANA, anti-CCP, rheumatoid factor, and myositis-specific antibodies if autoimmune myositis suspected 2
• Viral studies if clinically indicated 2
• Drug screening: document all medications, supplements, and recreational drug use including cocaine, methamphetamine, ecstasy, ketamine, and heroin 3

Critical Pitfalls to Avoid

• Delaying fluid resuscitation is the single most important error, associated with dramatically higher acute kidney injury risk 1
• Inadequate fluid volume (<6L/day in severe cases) fails to prevent renal complications 1
• Missing compartment syndrome in traumatic or severe cases leads to irreversible damage 1
• Failing to monitor and correct hyperkalemia can result in sudden cardiac arrest 1
• Using NSAIDs for pain worsens nephrotoxicity in already vulnerable kidneys 3, 1
• Assuming CK has peaked early - CK levels peak 24-120 hours after the inciting event, so early levels may not represent maximum severity 3

Disposition Considerations

Most patients require admission for aggressive fluid resuscitation and monitoring 4. Outpatient management may be considered only in very mild cases with CK <5,000 IU/L, normal renal function, no electrolyte abnormalities, and reliable follow-up, though this represents a minority of cases.