What are the recommended fluid administration rates for patients with rhabdomyolysis?

Fluid Administration Rates for Rhabdomyolysis

Aggressive intravenous fluid resuscitation at a rate of 1.5-2 L/hour initially, followed by maintenance at 200-300 mL/hour to achieve a urine output of at least 300 mL/hour, is the cornerstone of rhabdomyolysis treatment. 1, 2, 3

Initial Fluid Resuscitation

Adult Patients

• First hour: Isotonic saline (0.9% NaCl) at 15-20 mL/kg/hour (approximately 1-1.5 L in average adult)
• Subsequent hours:
  • If corrected serum sodium is normal or elevated: 0.45% NaCl at 4-14 mL/kg/hour
  • If corrected serum sodium is low: 0.9% NaCl at 4-14 mL/kg/hour
• Target urine output: At least 300 mL/hour (or 200-300 mL/hour) 1, 3

Pediatric Patients

• First hour: Isotonic saline (0.9% NaCl) at 10-20 mL/kg/hour
• Important limitation: Initial reexpansion should not exceed 50 mL/kg over first 4 hours
• Subsequent fluid therapy: Calculate to replace fluid deficit evenly over 48 hours
• Maintenance rate: 1.5 times the 24-hour maintenance requirements (approximately 5 mL/kg/hour) 4

Electrolyte Management

• Once renal function is confirmed and serum potassium is known, add 20-30 mEq/L potassium (2/3 KCl and 1/3 KPO₄) to IV fluids 4
• When serum glucose reaches 250 mg/dL (in diabetic patients with hyperglycemic crisis), change fluid to 5% dextrose with 0.45-0.75% NaCl 4

Duration of Therapy

• Continue aggressive IV fluid therapy until:
  • CK levels decrease to less than 1,000 U/L 1
  • Clinical improvement is observed
  • Urine clears of myoglobin

Monitoring Parameters

• Hemodynamic status (blood pressure, heart rate)
• Fluid input/output balance (strict hourly monitoring)
• Serum electrolytes (especially potassium, calcium, phosphate)
• Renal function (BUN, creatinine)
• Creatine kinase levels
• Urine output and color
• Mental status (especially in pediatric patients)
• Serum osmolality (change should not exceed 3 mOsm/kg/hour) 4

Special Considerations

• Cardiac or renal compromise: More cautious fluid administration with frequent assessment of cardiac, renal, and mental status to avoid iatrogenic fluid overload 4
• Compartment syndrome: May require surgical decompression (fasciotomy) 1, 2
• Bicarbonate administration: Not routinely recommended unless patient has metabolic acidosis 4, 2
• Mannitol: Not routinely recommended based on current evidence 2, 3

Common Pitfalls to Avoid

1. Delayed recognition: Dark urine, muscle pain, and weakness should immediately trigger suspicion of rhabdomyolysis 5
2. Inadequate fluid resuscitation: The most important intervention is early and aggressive fluid administration 2, 3
3. Overemphasis on urine alkalinization: Current evidence does not strongly support routine use of bicarbonate for this purpose 2, 6
4. Missing compartment syndrome: Requires vigilant monitoring and prompt surgical intervention if present 1, 2
5. Inadequate monitoring: Failure to monitor electrolytes, renal function, and fluid balance can lead to complications 7

By following these fluid administration guidelines, clinicians can effectively manage rhabdomyolysis and reduce the risk of acute kidney injury, which is the most significant complication of this condition.