What is the management of Acute Kidney Injury (AKI)?

Management of Acute Kidney Injury (AKI)

The management of AKI requires prompt identification of underlying causes, discontinuation of nephrotoxic medications, optimization of fluid status, and supportive care, with renal replacement therapy reserved for severe cases with specific indications. 1

Definition and Diagnosis

AKI is defined by KDIGO guidelines as:

• Increase in serum creatinine ≥0.3 mg/dL within 48 hours, OR
• Increase in serum creatinine ≥1.5 times baseline within 7 days, OR
• Urine output <0.5 mL/kg/hour for >6 hours 2, 1

Staging of AKI

Stage	Creatinine Criterion	Urine Output Criterion
1	Increase ≥0.3 mg/dL in 48h or 1.5-1.9× baseline	<0.5 mL/kg/h for >6h
2	Increase 2.0-2.9× baseline	<0.5 mL/kg/h for >12h
3	Increase ≥3.0× baseline, or ≥4.0 mg/dL, or RRT initiation	<0.3 mL/kg/h for ≥24h or anuria for ≥12h

Initial Assessment

1. Laboratory workup 1:

   • Serum creatinine and BUN
   • Complete blood count with differential
   • Serum electrolytes with calculated anion gap
   • Urinalysis with microscopy
   • Urine chemistry (sodium, creatinine for fractional excretion)

2. Imaging 1:

   • Renal ultrasound to rule out obstruction
   • Avoid contrast studies if possible

3. Categorize AKI 3, 4:

   • Prerenal (volume depletion, hypotension)
   • Intrinsic renal (ATN, glomerulonephritis, interstitial nephritis)
   • Postrenal (obstruction)

Management Protocol

1. Treat Underlying Cause

• Identify and treat precipitating factors such as infections, GI bleeding, excessive diuresis, volume depletion, and tense ascites 1
• Remove obstruction if present (urologic consultation for catheterization or stenting)

2. Medication Management

• Discontinue nephrotoxic medications immediately 1:

  • NSAIDs
  • Aminoglycosides
  • ACE inhibitors/ARBs
  • Contrast agents
  • Other nephrotoxic drugs

• Monitor therapeutic drug levels when using potentially nephrotoxic medications that cannot be discontinued 1

3. Fluid Management

• For hypovolemic patients: Administer isotonic crystalloids rather than colloids for initial volume expansion 2, 1
• For euvolemic or hypervolemic patients: Avoid excessive fluid administration 1
• For volume overload: Consider diuretics, but only for management of volume overload, not as AKI treatment 2, 1
• Dietary modifications: Restrict sodium to 2g daily or less; consider fluid restriction to 2L daily if persistent fluid retention despite diuretics 1

4. Hemodynamic Support

• Maintain adequate mean arterial pressure to ensure renal perfusion 1
• Consider vasopressors in hypotensive patients after adequate volume resuscitation 2
• Consider goal-directed fluid therapy in critically ill patients 1

5. Renal Replacement Therapy (RRT)

Indications for RRT include 1:

• Refractory hyperkalemia
• Volume overload unresponsive to diuretics
• Severe metabolic acidosis
• Uremic symptoms (encephalopathy, pericarditis, pleuritis)
• Certain toxin ingestions

The optimal timing, dose, and modality of RRT remains controversial and is an area of active investigation 2

Follow-up and Monitoring

• Evaluate kidney function 3 months after an AKI episode to screen for development of chronic kidney disease 1
• Adjust medications as kidney function recovers 1
• Higher risk populations requiring closer follow-up 2, 1:
  • Patients with Stage 3 AKI
  • Patients with baseline chronic kidney disease
  • Patients with incomplete recovery of kidney function at discharge
  • Pediatric patients

Prognosis

• AKI is not a self-limited process but strongly linked to increased risk for chronic kidney disease, subsequent AKI, and future mortality 1, 5
• Higher stages of AKI are associated with higher risk of mortality 1
• Presence of proteinuria indicates worse prognosis 1
• Comorbidities such as diabetes significantly worsen outcomes 1

Common Pitfalls to Avoid

1. Delaying identification and treatment of underlying cause
2. Continuing nephrotoxic medications
3. Excessive fluid administration in euvolemic or hypervolemic patients
4. Using diuretics as treatment for AKI rather than for volume management
5. Failing to follow up patients after an AKI episode
6. Underestimating the long-term consequences of even a single AKI episode

The management of AKI requires a systematic approach focused on identifying and treating the underlying cause while providing appropriate supportive care to prevent further kidney damage and associated complications.