How is rhabdomyolysis with hypernatremia managed?

Management of Rhabdomyolysis with Hypernatremia

Immediate Fluid Resuscitation Strategy

In patients with rhabdomyolysis and hypernatremia, initiate aggressive intravenous fluid resuscitation with hypotonic fluids (0.45% NaCl) to simultaneously address free water deficit and prevent acute kidney injury, while carefully controlling the rate of sodium correction to avoid cerebral edema. 1, 2

Initial Fluid Selection and Administration

• Start with hypotonic saline (0.45% NaCl) rather than isotonic saline, as isotonic fluids will worsen hypernatremia in patients with free water deficits 1
• Administer aggressive fluid volumes: patients with severe rhabdomyolysis (CPK >15,000 IU/L) may require >6L per day to prevent acute kidney injury, while moderate rhabdomyolysis requires 3-6L per day 3
• Never use isotonic (0.9%) saline as initial therapy in hypernatremic patients, as this exacerbates the hypernatremia 1
• Early initiation of volume resuscitation is critical—delayed fluid therapy is associated with higher rates of acute kidney injury in rhabdomyolysis 3, 2

Rate of Sodium Correction

• Target correction rate of 10-15 mmol/L per 24 hours for chronic hypernatremia to prevent cerebral edema 1
• Acute hypernatremia (<48 hours duration) can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• Slower correction is critical in chronic cases because brain cells synthesize intracellular osmolytes over 48 hours to adapt; rapid correction causes cerebral edema, seizures, and permanent neurological injury 1
• Monitor serum sodium every 2-4 hours during active correction 1

Monitoring and Laboratory Assessment

Essential Serial Measurements

• Measure creatine phosphokinase (CPK) serially for early detection and monitoring of rhabdomyolysis severity 3, 4
• Monitor plasma myoglobin levels alongside CPK 3
• Check serum potassium frequently as rhabdomyolysis causes hyperkalemia from muscle cell destruction, which can be life-threatening 3, 5, 6
• Assess renal function with serum creatinine and blood urea nitrogen 3
• Monitor serum sodium, chloride, and bicarbonate levels regularly during treatment 1

Urine Monitoring

• Place bladder catheter to monitor hourly urine output 3
• Maintain urine pH ≥6.5 to prevent myoglobin precipitation in renal tubules 3
• Check urine osmolality to assess renal concentrating ability 1

Specific Interventions to Avoid

Bicarbonate and Mannitol

• Do not routinely administer sodium bicarbonate for urine alkalinization—evidence shows no improvement in acute renal failure or dialysis rates 2
• Do not routinely use mannitol—no benefit demonstrated for preventing acute kidney injury in rhabdomyolysis 2, 5
• These interventions lack high-quality evidence and are conditionally recommended against 2

Isotonic Fluid Caution

• Avoid high volumes of isotonic (0.9%) saline in hypernatremic patients, as this delays recovery and can worsen outcomes 7
• The concern over rhabdomyolysis progression should not dictate use of isotonic fluids when hypernatremia is present 7

Management of Complications

Hyperkalemia

• Treat hyperkalemia aggressively as it represents a life-threatening complication of rhabdomyolysis 5, 6
• Consider acute hemodialysis for severe hyperkalemia unresponsive to medical management 6
• Hemodialysis can also address severe hypernatremia when needed, though rapid sodium correction during dialysis requires careful monitoring 6

Compartment Syndrome

• Investigate for compartment syndrome every 30-60 minutes during the first 24 hours in patients with crush injury, fracture, or reperfusion injury 3
• Look for pain (especially with passive stretch), tension, paresthesia, and paresis—these are early signs 3
• Measure compartment pressure if clinical suspicion exists: pressure >30 mmHg or differential pressure (diastolic BP - compartment pressure) <30 mmHg indicates compartment syndrome 3
• Perform early fasciotomy for established compartment syndrome 3

Acute Kidney Injury

• Aggressive intravenous fluid resuscitation decreases the incidence of acute renal failure and need for dialysis 2
• Maintain adequate urine output through volume resuscitation rather than loop diuretics 5
• Monitor for progression to renal replacement therapy needs 3

Clinical Pitfalls

• Do not correct chronic hypernatremia too rapidly—this is the most dangerous error, leading to cerebral edema and seizures 1
• Do not withhold hypotonic fluids due to concern about rhabdomyolysis—the hypernatremia must be addressed with appropriate fluid composition 7
• Do not assume isotonic fluids are safer—they worsen hypernatremia and delay recovery 1, 7
• Concern over central pontine myelinolysis from rapid correction in exercise-associated hyponatremia is unsupported, but this does not apply to hypernatremia correction, where slow correction remains essential 7