What is the management approach for an adult patient with suspected acute kidney injury (AKI), possibly due to rhabdomyolysis, and no specified past medical history?

Management of Acute Kidney Injury in Rhabdomyolysis

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

Immediate Fluid Resuscitation Strategy

Start fluid resuscitation as early as possible, as delayed initiation is strongly associated with higher risk of acute kidney injury. 1, 2

• Use isotonic crystalloids (0.9% normal saline) rather than colloids (albumin or starches) for initial volume expansion. 4
• For severe rhabdomyolysis with CK >15,000 IU/L, administer >6L of intravenous fluids per day. 1, 2
• For moderate rhabdomyolysis, administer 3-6L of intravenous fluids per day. 1, 2
• In acute settings (e.g., crush injury), infuse 1000 mL/hour during initial extrication, then reduce by at least 50% if extrication exceeds 2 hours to avoid volume overload. 1

Target urine output of ≥300 mL/hour (approximately 3-5 mL/kg/hour for a 70 kg patient)—this is 6-10 times higher than standard oliguria thresholds and is necessary to ensure adequate myoglobin clearance and prevent tubular precipitation. 1, 3

Fluid Type Selection: Critical Considerations

Avoid potassium-containing fluids such as Lactated Ringer's solution, Hartmann's solution, and Plasmalyte A, as potassium levels may increase markedly after reperfusion even with intact renal function. 1

Avoid starch-based colloid solutions due to their association with increased rates of AKI and bleeding complications. 4, 1

After initial resuscitation with normal saline, fluid choice should be adjusted based on hydration status and serum electrolyte levels. 1

What NOT to Use: Interventions Without Proven Benefit

Do not routinely use urinary alkalinization with sodium bicarbonate, as current evidence does not demonstrate benefit over aggressive fluid resuscitation with crystalloids alone. 1, 5

• Large doses of bicarbonate can worsen hypocalcemia by decreasing free calcium levels. 1
• Bicarbonate adds extra volume without proven benefit. 1

Do not routinely use mannitol, as studies suggest little additional benefit compared to crystalloid resuscitation alone, and it is potentially nephrotoxic. 1, 5, 6

• Mannitol may only benefit patients with markedly elevated CK (>30,000 U/L), though this benefit remains undefined. 1
• Mannitol is contraindicated in patients with oligoanuria. 4

Do not routinely use loop diuretics for prevention or treatment of rhabdomyolysis-induced AKI, as they may increase the risk of AKI unless adequate volume resuscitation has first been achieved. 1, 5

• Diuretics should only be considered after adequate volume expansion for management of volume overload, not as primary treatment. 1

Monitoring Parameters

Insert a bladder catheter to monitor hourly urine output unless there is evidence of urethral injury. 1

Perform repeated bioassessments including:

• Plasma myoglobin, creatine kinase (CK), and potassium levels. 2
• Complete electrolyte panel including calcium, phosphorus, and magnesium—hyperkalemia can lead to life-threatening cardiac arrhythmias. 2, 3
• Serum creatinine and urine output to assess for AKI development. 4
• Urine pH, which should be maintained at approximately 6.5. 1

Monitor for compartment syndrome, especially in trauma patients: pain, tension, paresthesia, and paresis are early signs; pulselessness and pallor are late signs indicating irreversible damage. 2

Renal Replacement Therapy Indications

Initiate RRT emergently for life-threatening changes in fluid, electrolyte, and acid-base balance. 4

Specific indications include:

• Fluid overload despite conservative management. 1
• Severe hyperkalemia refractory to medical management. 2
• Severe metabolic acidosis. 3

Intermittent hemodialysis is the preferred modality in rhabdomyolysis, as it provides rapid clearance of potassium and allows treatment of several patients per day on the same machine. 1

Medication Management

Immediately discontinue any causative agents, particularly:

• Statins and other prescription medications associated with rhabdomyolysis. 2
• Dietary supplements including red yeast rice (containing lovastatin), creatine monohydrate, wormwood oil, licorice, and Hydroxycut. 2

Avoid succinylcholine in patients with rhabdomyolysis or at risk for malignant hyperthermia. 2

Pain Management Approach

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 patients already at high risk for AKI. 2

Avoid all NSAIDs (ibuprofen, ketoprofen, diclofenac, naproxen, mefenamic acid) due to their gastrointestinal and renal toxicity. 2

Reserve opioids for severe muscle pain unresponsive to acetaminophen; oral morphine is first-line (20-40 mg for opioid-naive patients), but use fentanyl or buprenorphine if eGFR <30 mL/min. 2

Common Pitfalls to Avoid

Do not delay fluid resuscitation waiting for laboratory confirmation—start immediately based on clinical suspicion. 1, 2

Do not use overly cautious fluid administration in fear of volume overload—aggressive hydration is the cornerstone of preventing AKI in rhabdomyolysis. 1, 3

Recognize that CK levels peak 24-120 hours after the inciting event—early levels may not represent the peak, and repeat measurement at 24 hours is essential if clinical suspicion remains high. 2, 3

Impact trauma can elevate CK without true rhabdomyolysis, but given rising trends, assume true muscle breakdown until proven otherwise. 2

Monitor for delayed complications including myonecrosis with calcium overload, myoglobinuric renal failure requiring dialysis, and compartment syndrome requiring fasciotomy. 2