What is the treatment for hyperkalemia, acute kidney injury, and elevated creatine kinase after a lower leg fracture?

Management of Hyperkalemia, AKI, and Elevated CK Following Lower Leg Fracture

Immediate aggressive fluid resuscitation with isotonic saline at 200-300 mL/hour to maintain urine output >200-300 mL/hour is the cornerstone of treatment for this patient with rhabdomyolysis-induced hyperkalemia and AKI. 1

Initial Assessment and Management of Hyperkalemia (K+ 5.6 mEq/L)

Immediate Interventions for Hyperkalemia

1. Stabilize cardiac membrane:

   • Administer IV calcium gluconate 10% (10 mL over 2-3 minutes) if ECG changes are present
   • Monitor ECG continuously

2. Shift potassium intracellularly:

   • Administer insulin 10 units IV with 50 mL of 50% dextrose
   • Consider nebulized beta-agonists (albuterol 10-20 mg)
   • Sodium bicarbonate 50 mEq IV if metabolic acidosis is present

3. Remove potassium from body:

   • Sodium polystyrene sulfonate 15-60g orally or 30-50g rectally 2
   • Note: Sodium polystyrene sulfonate should not be used as emergency treatment for life-threatening hyperkalemia due to its delayed onset of action 2

Avoid Potassium-Containing Solutions

• Potassium-containing balanced salt fluids such as Lactated Ringer's solution, Hartmann's solution, and Plasmalyte A must be avoided as they may worsen hyperkalemia 3
• Use 0.9% saline for fluid resuscitation

Management of Rhabdomyolysis and AKI

Fluid Resuscitation

• Initiate aggressive fluid resuscitation with isotonic saline at 200-300 mL/hour 1
• Target urine output >200-300 mL/hour
• Continue fluid resuscitation until CK levels decrease to <1,000 U/L 1
• Monitor for volume overload, especially in elderly patients or those with cardiac issues 1

Medication Management

• Discontinue nephrotoxic medications (NSAIDs, aminoglycosides, etc.) 3
• Adjust dosing of medications cleared by kidneys 1
• Do not add potassium to IV fluids until adequate renal function is confirmed 1

Monitoring Parameters

• Check serum electrolytes, creatinine, BUN, and CK every 6-12 hours 1
• Monitor urine output hourly
• Perform frequent neurovascular checks of the affected limb to assess for compartment syndrome 1
• Consider measuring compartment pressures if clinical suspicion for compartment syndrome

Indications for Renal Replacement Therapy

Consider hemodialysis for any of the following:

• Persistent hyperkalemia (>6.0 mEq/L) despite medical management 3
• Severe metabolic acidosis (pH <7.1)
• Volume overload unresponsive to diuretics
• Uremic symptoms
• Rapidly rising BUN/creatinine despite appropriate fluid resuscitation

Intermittent hemodialysis is preferred for hyperkalemia due to its rapid potassium clearance 3

Compartment Syndrome Assessment

• Perform frequent neurovascular checks of the affected limb
• Monitor for the 6 P's: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, and Poikilothermia
• Consider surgical consultation for decompressive fasciotomy if compartment pressure >30 mmHg or differential pressure (diastolic BP - compartment pressure) <30 mmHg 1

Pitfalls to Avoid

1. Delayed recognition of rhabdomyolysis: CK levels may not peak until 24-72 hours after muscle injury 1
2. Inadequate fluid resuscitation: Most common preventable cause of AKI in rhabdomyolysis 1
3. Using potassium-containing fluids: Can worsen hyperkalemia 3
4. Relying solely on serum creatinine: May underestimate kidney injury in patients with low muscle mass 4
5. Delaying treatment for hyperkalemia: Life-threatening arrhythmias can occur rapidly
6. Missing compartment syndrome: Can lead to further muscle damage and worsen rhabdomyolysis

Prognosis

Prognosis depends on:

• Duration of immobility after fracture
• Extent of muscle damage (reflected by CK levels)
• Promptness of treatment
• Development of complications
• Pre-existing conditions

Early recognition and aggressive fluid resuscitation significantly improve outcomes and prevent progression to severe AKI 1, 5.