Treatment of Myoglobinuria
The treatment of myoglobinuria should focus on aggressive intravenous fluid resuscitation with normal saline, aiming for a urine output of >2 ml/kg/h, and sodium bicarbonate administration to alkalinize the urine and prevent acute kidney injury. 1
Immediate Management
Initial Assessment and Treatment
- Identify the underlying cause (rhabdomyolysis, malignant hyperthermia, exertional injury)
- Insert urinary catheter to monitor urine output and check for myoglobinuria (cola-colored urine)
- Obtain baseline laboratory tests:
- Creatine kinase (CK) levels
- Renal function (creatinine, BUN)
- Electrolytes (particularly potassium)
- Arterial blood gas analysis
Fluid Resuscitation
- Administer intravenous normal saline at 400 ml/hour initially, with adjustments between 200-1000 ml/hour based on severity 2
- Target urine output of >2 ml/kg/h 1
- Continue aggressive hydration until myoglobinuria resolves and CK levels decrease significantly
Specific Interventions
Urine Alkalinization
- Administer sodium bicarbonate to alkalinize urine 1
- Myoglobin is less likely to precipitate in alkaline urine, reducing risk of tubular obstruction
- Although controversial, the 2021 Association of Anaesthetists guideline recommends sodium bicarbonate use in the absence of convincing evidence for harm 1
Management of Complications
Hyperkalaemia
- Monitor potassium levels closely
- If hyperkalaemia develops:
- Administer sodium bicarbonate
- Consider glucose (50 ml of 50%) with insulin (10 units)
- Avoid calcium administration except in extreme cases 1
Compartment Syndrome
- Regularly assess limbs for swelling, muscle softness, and peripheral pulses
- Monitor for pain in awake patients
- If compartment syndrome is suspected, measure compartmental pressures
- Perform fasciotomies if compartment syndrome develops 1
Advanced Interventions
Renal Replacement Therapy
- Consider hemofiltration if hyperkalaemia is not controlled with medical management 1
- Continuous venovenous hemofiltration (CVVH) can effectively remove myoglobin (sieving coefficient ~0.6) 3
- CVVH at a rate of 2-3 L/h using an AN69 hemofilter has been shown to remove significant amounts of myoglobin 3
Monitoring and Follow-up
- Monitor urine output hourly
- Check CK levels daily until normalizing
- Monitor renal function and electrolytes regularly
- Continue treatment until myoglobinuria resolves and CK levels decrease significantly
- Remember that CK levels may not peak until up to 24 hours after the initial event 1
Special Considerations
Malignant Hyperthermia-Associated Myoglobinuria
- Discontinue triggering agents immediately
- Administer dantrolene (2-3 mg/kg initially, then 1 mg/kg as needed) 1
- Treat metabolic derangements (acidosis, hyperkalaemia)
- Monitor for disseminated intravascular coagulation 1
Exertional Rhabdomyolysis
- Rest affected muscle groups
- Gradual return to activity only after complete resolution of symptoms and normalization of CK levels 2
Pitfalls and Caveats
- Do not delay treatment while awaiting laboratory confirmation
- Avoid volume overload in patients with cardiac or renal dysfunction
- Differentiate myoglobinuria from hemoglobinuria (both can cause dark urine) 4
- Remember that recovery of muscle and renal function is usually complete in patients who survive the acute phase 5