What is the target urine output in a trauma patient with elevated Creatine Kinase (CK) levels?

Target Urine Output in Trauma Patients with Elevated Creatine Kinase

In trauma patients with elevated CK levels indicating rhabdomyolysis, maintain a urine output of at least 300 mL/hour (approximately 3-5 mL/kg/hour for a 70 kg patient) through aggressive intravenous fluid resuscitation to prevent acute kidney injury. 1

Aggressive Fluid Resuscitation Strategy

The cornerstone of management is early and aggressive intravenous fluid administration:

• Administer >6L of intravenous fluids per day for severe rhabdomyolysis (CK >30,000 U/L or significantly elevated levels) to prevent acute kidney injury and need for renal replacement therapy 2, 3
• Begin with isotonic saline (0.9% NaCl) for initial volume expansion 3
• Start fluid resuscitation as early as possible, as delayed initiation is associated with higher risk of acute kidney injury 3

Urine Output Monitoring and Targets

The target urine output in rhabdomyolysis differs substantially from standard AKI definitions:

• Target urine output: ≥300 mL/hour to ensure adequate myoglobin clearance and prevent tubular precipitation 1
• This translates to approximately 3-5 mL/kg/hour for an average 70 kg patient, which is 6-10 times higher than the standard oliguria threshold of 0.5 mL/kg/hour used in general AKI definitions 4, 5
• Use bladder catheterization to monitor hourly urine output precisely 2, 3

Clinical Context for Trauma Patients

Trauma patients with penetrating injuries are at particularly high risk:

• 13% of penetrating trauma ICU patients develop significant rhabdomyolysis (CK ≥5,000 U/L) 6
• Patients with vascular and severe extremity injury have a sixfold increased risk of developing significant rhabdomyolysis 6
• These patients experience higher rates of renal failure (23% vs 7%) and longer ICU stays 6

Additional Monitoring Parameters

Beyond urine output, monitor the following:

• Serial CK levels every 6-12 hours until declining below 1,000 U/L 2, 1
• Plasma myoglobin and potassium levels 3
• Maintain urine pH at approximately 6.5 if possible 2, 3
• Monitor for compartment syndrome, which can develop as an early or late complication in trauma patients 2, 1

When Standard Fluid Resuscitation Fails

If urine output remains inadequate (<300 mL/hour) despite aggressive fluid administration:

• Consider mannitol only after adequate volume expansion has been achieved, particularly for CK >30,000 U/L, though benefit remains undefined 3
• Mannitol is contraindicated in oligoanuria 3
• Initiate renal replacement therapy if oliguria persists despite 4 days of adequate hydration, as this indicates severe rhabdomyolysis with potential for irreversible kidney damage 2

Critical Pitfalls to Avoid

• Do not use standard AKI oliguria definitions (0.5 mL/kg/hour) as targets in rhabdomyolysis—this is inadequate for myoglobin clearance 1
• Delayed fluid resuscitation is associated with increased risk of acute kidney injury 3
• Excessive fluid administration in patients with cardiac compromise can cause fluid overload—monitor for pulmonary edema 2, 3
• Failure to monitor and correct hyperkalemia can lead to fatal cardiac arrhythmias 2, 3

Duration of Aggressive Fluid Therapy

• Continue intravenous fluids until CK levels decline below 1,000 U/L 1
• This typically requires several days of intensive fluid management
• Reassess volume status frequently to balance adequate perfusion against fluid overload risk 2