What is the management for myoglobinuria (presence of myoglobin in urine) after a caesarean section?

Management of Myoglobinuria After Caesarean Section

The primary management of myoglobinuria after caesarean section requires aggressive fluid resuscitation targeting urine output >2 mL/kg/h, urinary alkalinization with sodium bicarbonate, and close monitoring for acute kidney injury and compartment syndrome.

Immediate Assessment and Monitoring

• Insert a urinary catheter to monitor urine output, urine pH, and assess for myoglobinuria 1
• Obtain arterial blood gas analysis, serum creatinine, blood urea nitrogen (BUN), creatine kinase (CK), electrolytes, and coagulation studies 1
• Monitor for the characteristic cola-colored or red-brown urine that indicates myoglobinuria 2, 3
• Use dipstick testing to rapidly confirm myoglobinuria presence 4
• Note that creatine kinase levels may not peak until 24 hours after the inciting event 1

Fluid Management Strategy

Target aggressive fluid resuscitation to achieve urine output >2 mL/kg/h 1

• High urine output is essential to prevent myoglobin precipitation in renal tubules and subsequent acute kidney injury 1
• Patients who respond to initial fluid resuscitation with increased urine output have significantly better outcomes and typically avoid dialysis 5
• Non-responders to fluid therapy demonstrate more severe muscle injury (higher CPK levels) and hemoconcentration, requiring an average of 5.3 dialysis sessions 5

Urinary Alkalinization

Administer sodium bicarbonate to alkalinize urine and prevent myoglobin precipitation 1

• Myoglobin is less likely to precipitate in alkaline urine, reducing the risk of acute kidney injury 1
• While controversy exists regarding alkalinization efficacy, the absence of convincing evidence for harm supports its use 1
• Sodium bicarbonate also aids potassium reuptake into cells if hyperkalaemia develops 1
• Historical data shows that mannitol-sodium bicarbonate infusion can alter the clinical course of myoglobinuric acute renal failure 5

Monitor for Complications

Acute Kidney Injury

• Serial monitoring of serum creatinine and BUN is essential 4
• Elevated creatine kinase activity (up to 150 times normal) with myoglobinuria indicates high risk for acute renal failure 4
• Four of the most severely affected patients in one series developed acute renal failure requiring dialysis 4

Compartment Syndrome

Any patient with myoglobinuria requires clinical monitoring for compartment syndrome development 1

• In awake patients, monitor for complaints of severe limb pain 1
• In sedated patients, regularly assess limbs for swelling, muscle softness, peripheral pulses, and oxygen saturation 1
• Measure compartmental pressures if compartment syndrome is suspected 1
• Treatment requires urgent fasciotomies 1

Electrolyte Abnormalities

• Monitor for hyperkalaemia, which can result from massive muscle breakdown 1
• Elevated serum phosphate levels indicate more severe muscle injury and worse prognosis 5

Context-Specific Considerations

While the provided evidence primarily addresses myoglobinuria in the context of malignant hyperthermia 1, the fundamental management principles apply to myoglobinuria from any cause after caesarean section, including:

• Prolonged positioning during surgery
• Muscle compression or ischemia
• Unrecognized malignant hyperthermia
• Pre-existing muscle disorders
• Severe pre-eclampsia/HELLP syndrome with muscle involvement

Critical Pitfalls to Avoid

• Do not delay fluid resuscitation - early aggressive treatment prevents acute renal failure 5
• Do not assume normal initial creatinine excludes risk - CK elevation precedes renal dysfunction 4
• Do not miss compartment syndrome - requires high clinical suspicion and regular assessment 1
• Do not discharge patients prematurely - continued monitoring for at least 24 hours is essential given delayed CK peaks 1