What is myoglobinuria and how is it managed?

What is Myoglobinuria and How to Manage It

Myoglobinuria is the presence of myoglobin in urine, appearing as cola-colored urine, caused by muscle damage that releases myoglobin into the bloodstream. The most important treatment is aggressive intravenous fluid resuscitation with normal saline to prevent acute kidney injury. 1

What is Myoglobin?

Myoglobin is a small, dark red, oxygen-binding protein found in skeletal and cardiac muscle. When muscle cells are damaged, myoglobin leaks into the bloodstream and is filtered by the kidneys into the urine, giving it a dark cola-like color. 2, 3

Causes of Myoglobinuria

Myoglobinuria happens when muscles break down (called rhabdomyolysis). This can be caused by:

• Intense physical exercise, especially eccentric exercises like running downstairs 2
• Muscle trauma or crush injuries
• Medications and toxins
• Metabolic disorders
• Infections
• Prolonged seizures
• Muscle diseases

How to Recognize Myoglobinuria

• Dark, cola-colored urine - This is the most obvious sign
• Muscle pain and weakness
• Muscle swelling
• Fatigue
• In severe cases, symptoms of kidney problems may develop

Differentiating from Hemoglobinuria

It's important to tell the difference between myoglobinuria (myoglobin in urine) and hemoglobinuria (hemoglobin in urine), as they require different treatments: 4

• Both can cause dark urine
• Laboratory tests can differentiate between them
• Myoglobin is cleared from blood more rapidly than hemoglobin

Management of Myoglobinuria

Immediate Treatment

1. Aggressive IV fluid resuscitation 1

   • Use normal saline
   • Target urine output >2 ml/kg/hour
   • This helps flush myoglobin through kidneys before it causes damage

2. Urine alkalinization 1

   • Administer sodium bicarbonate
   • Makes myoglobin less likely to cause kidney damage
   • Myoglobin is less likely to precipitate in alkaline urine

3. Monitor and manage electrolyte imbalances 1

   • Watch potassium levels closely
   • If hyperkalemia develops:
     • Give sodium bicarbonate
     • Consider glucose with insulin
     • Avoid calcium except in extreme cases

Ongoing Management

• Monitor urine output hourly
• Check creatine kinase (CK) levels daily until normalizing
• Regular monitoring of kidney function and electrolytes
• Continue treatment until myoglobinuria resolves and CK levels decrease significantly 1

For Severe Cases

• Consider renal replacement therapy (hemofiltration) if hyperkalemia cannot be controlled medically 1
• Watch for compartment syndrome (swelling within muscle compartments):
  • Check limbs for swelling, muscle softness, and pulses
  • Measure compartment pressures if suspected
  • Perform fasciotomies if necessary 1

Prevention

• Avoid excessive eccentric exercise (like downhill running, squatting, trampolining) 2
• Stay well hydrated during exercise
• Avoid known triggers if you have had myoglobinuria before
• If you have a muscle disease, follow medical advice about exercise limitations

When to Seek Medical Help

Get emergency medical care if you notice:

• Dark cola-colored urine
• Severe muscle pain with weakness
• Decreased urine output
• Confusion or extreme fatigue

Remember that prompt treatment is essential to prevent kidney damage, which is the most serious complication of myoglobinuria. 3