What is the immediate management for a patient presenting with rhabdomyolysis, as indicated by elevated Creatine Kinase (CK) levels?

Immediate Management of Rhabdomyolysis with Elevated CK

Initiate aggressive intravenous fluid resuscitation immediately with isotonic saline (0.9% NaCl) at high rates—for severe rhabdomyolysis (CK >15,000 IU/L), administer >6L per day; for moderate cases (CK 5,000-15,000 IU/L), give 3-6L per day—targeting urine output ≥300 mL/hour to prevent acute kidney injury. 1, 2

Initial Resuscitation Strategy

Start fluid resuscitation as early as possible, as delayed initiation is directly associated with higher risk of acute kidney injury. 1, 2 Begin with 0.9% normal saline at 1000 mL/hour initially if the patient presents acutely. 2 The large CK molecule (82 kDa) clears slowly through lymphatic mechanisms, meaning CK levels may still be rising and have not yet peaked—levels typically peak 24-120 hours after the inciting event. 1

Fluid Type Selection

• Use isotonic saline (0.9% NaCl) exclusively for initial volume expansion 2
• Avoid potassium-containing solutions (Lactated Ringer's, Hartmann's solution, Plasmalyte A) because potassium levels can increase markedly after muscle breakdown, even with intact renal function 2
• Avoid starch-based fluids due to association with increased rates of acute kidney injury 2

Target Urine Output and Monitoring

Establish a target urine output of ≥300 mL/hour (approximately 3-5 mL/kg/hour for a 70 kg patient), which is 6-10 times higher than standard oliguria thresholds used in general acute kidney injury. 2 This aggressive target ensures adequate myoglobin clearance and prevents tubular precipitation. 2

Essential Monitoring Parameters

• Insert a bladder catheter immediately to monitor hourly urine output 2
• Trend CK, creatinine, and electrolytes (especially potassium) every 6-12 hours in severe cases until CK is declining and renal function stabilizes 1, 2
• Monitor for hyperkalemia emergently, as this can precipitate life-threatening cardiac arrhythmias 1
• Obtain an ECG to evaluate for hyperkalemia-related changes 3

Medication Management

Immediately discontinue any causative agents, particularly:

• Statins and other prescription medications 1
• Dietary supplements: red yeast rice containing lovastatin, creatine monohydrate, wormwood oil, licorice, and Hydroxycut 1
• NSAIDs, which should be avoided due to nephrotoxic effects in patients already at high risk for acute kidney injury 1

What NOT to Do: Common Pitfalls

Do not routinely use sodium bicarbonate for urinary alkalinization—current evidence does not demonstrate benefit over aggressive fluid resuscitation with crystalloids alone, and large doses can worsen hypocalcemia by decreasing free calcium levels. 2 Bicarbonate is reserved only for life-threatening hyperkalemia or severe metabolic acidosis. 2

Do not routinely use mannitol—studies suggest little additional benefit compared to crystalloid resuscitation alone, and it is potentially nephrotoxic. 2, 4 Mannitol may only benefit patients with markedly elevated CK (>30,000 U/L), though even this benefit remains undefined. 2

Do not use diuretics as primary treatment—diuresis may increase the risk of acute kidney injury unless adequate volume resuscitation has first been achieved. 2 Diuretics should only be considered after adequate volume expansion for management of volume overload, not as primary rhabdomyolysis treatment. 2

Pain Management

Use acetaminophen (500-1000 mg) as the preferred initial analgesic, with a maximum daily dose of 4-6 grams, as it avoids nephrotoxic effects particularly problematic in rhabdomyolysis patients. 1 Avoid all NSAIDs (ibuprofen, ketoprofen, diclofenac, naproxen, mefenamic acid) due to gastrointestinal and renal toxicity. 1

For severe pain unresponsive to acetaminophen, use oral morphine (20-40 mg for opioid-naive patients) as first-line opioid. 1 If acute kidney injury develops with eGFR <30 mL/min, switch to fentanyl or buprenorphine as the safest opioid choices. 1

Severity Stratification

The volume of fluid required depends on CK level:

• CK >15,000 IU/L (severe): >6L per day 1, 2
• CK 5,000-15,000 IU/L (moderate): 3-6L per day 1, 2

Note that CK levels can reach extremely high values (>500,000 IU/L) without necessarily causing acute kidney injury if aggressive fluid resuscitation is initiated early. 5, 6 The key protective factor is early, aggressive volume expansion. 6, 3, 4

Indications for Renal Replacement Therapy

Initiate dialysis for:

• Fluid overload despite conservative management 2
• Life-threatening hyperkalemia unresponsive to medical management 2
• Severe metabolic acidosis 2

Intermittent hemodialysis is the preferred modality as it provides rapid clearance of potassium and allows treatment of multiple patients per day on the same machine. 2

Special Considerations for Trauma Patients

If the mechanism suggests potential for progressive rhabdomyolysis (crush injury, prolonged immobilization), initiate crystalloid fluid resuscitation immediately even if current CK is only mildly elevated, as levels will continue to rise. 1 In trauma settings, establish IV access before extrication is complete and infuse 0.9% normal saline at 1000 mL/hour during initial extrication. 2