What are the diagnosis and management strategies for rhabdomyolysis, including the target urine output?

From the Guidelines

Rhabdomyolysis should be diagnosed and managed with aggressive intravenous fluid resuscitation, aiming for a target urine output of 200-300 mL/hour, and urine pH maintenance at 6.5, as recommended by recent guidelines 1. The diagnosis of rhabdomyolysis involves a combination of clinical presentation, laboratory tests, and monitoring of urine output. Key laboratory tests include:

• Plasma myoglobin measurements
• Plasma creatine phosphokinase (CPK) measurements
• Kalaemia measurements
• Urine pH monitoring According to the guidelines for the acute care of severe limb trauma patients 1, bladder catheterization is recommended to monitor hourly urine output and urine pH. Management strategies for rhabdomyolysis include:
• Aggressive intravenous fluid resuscitation with isotonic saline
• Target urine output of 200-300 mL/hour
• Maintenance of urine pH at 6.5
• Monitoring of serum electrolytes, particularly potassium, calcium, and phosphorus
• Correction of electrolyte imbalances as needed
• Consideration of urine alkalinization with sodium bicarbonate in severe cases
• Renal replacement therapy (dialysis) for patients with severe hyperkalemia, acidosis, or volume overload unresponsive to medical management. The underlying cause of rhabdomyolysis must be identified and addressed, and CK levels should be monitored daily until declining, with adjustments to fluid administration based on urine output, vital signs, and electrolyte status 1.

From the Research

Diagnosis of Rhabdomyolysis

• Rhabdomyolysis is a potentially life-threatening condition caused by a breakdown of skeletal muscle and the release of the intracellular contents into the circulatory system 2
• The diagnosis should be considered when patients present with circumstances known to be high-risk for rhabdomyolysis, including crush injury, excessive muscular activity, medications, infections, and varied metabolic, connective tissue, rheumatologic, and endocrine disorders 2

Management of Rhabdomyolysis

• Aggressive intravenous fluid resuscitation (IVFR) is recommended to improve outcomes of acute renal failure (ARF) and lessen the need for dialysis in patients with rhabdomyolysis 3
• The goal of IVFR is to stabilize the circulation, mobilize edema fluids sequestered in the injured muscles into the circulation, correct hyperkalemia and acidosis, and protect against the nephrotoxic effects of myoglobinemia and hyperuricosuria 4
• Early vigorous fluid resuscitation with ≥12 l daily intravenous infusion of alkaline solution started at the scene of injury can prevent myoglobinuric acute kidney injury (AKI) and reduce mortality 4

Urine Output Goal

• The target urine output for patients with rhabdomyolysis is not explicitly stated in the provided studies, but aggressive IVFR aims to achieve a high urine output to prevent myoglobinuric renal failure 3, 4
• The use of bicarbonate or mannitol is not recommended as it does not improve the incidence of acute renal failure and need for dialysis in patients with rhabdomyolysis 3

Additional Considerations

• Serum potassium levels must be obtained and electrocardiograms must be evaluated to identify life- and limb-threatening complications of hyperkalemia 2
• Optimal crystalloid selection is still debated, but immediate, aggressive intravenous volume expansion is indicated to prevent myoglobinuric renal failure 2