Initial Management of Acute Kidney Injury (AKI)
The initial steps in managing AKI should include withdrawal of nephrotoxic medications, optimization of volume status with isotonic crystalloids, and identification of the underlying cause to guide specific treatment. 1
Definition and Diagnosis
AKI is defined by:
- Increase in serum creatinine ≥0.3 mg/dL within 48 hours
- Increase in serum creatinine ≥1.5 times baseline within 7 days
- Urine output <0.5 mL/kg/h for 6 hours or more 1
AKI is classified into three stages based on severity:
| Stage | Serum Creatinine | Urine Output |
|---|---|---|
| 1 | Increase ≥0.3 mg/dL or 1.5-1.9× baseline | <0.5 mL/kg/h for 6-12h |
| 2 | 2.0-2.9× baseline | <0.5 mL/kg/h for ≥12h |
| 3 | ≥3.0× baseline or ≥4.0 mg/dL or RRT initiation | <0.3 mL/kg/h for ≥24h or anuria for ≥12h |
Step-by-Step Management Algorithm
1. Immediate Interventions
- Withdraw all potentially nephrotoxic medications (NSAIDs, ACEi/ARBs, vasodilators) 1
- Discontinue diuretics, especially in hypovolemic patients 1
- Assess volume status and correct hypovolemia or hypervolemia
2. Fluid Management
- Administer isotonic crystalloids (normal saline or balanced solutions) for initial volume expansion 1
- For patients with cirrhosis and AKI:
- Avoid hydroxyethyl starches which increase AKI incidence 1
3. Hemodynamic Support
- Use vasopressors with fluids for hemodynamic instability 1
- Implement protocol-based management of hemodynamic parameters 1
4. Medication Management
- Adjust medication doses based on estimated GFR 1
- For specific medications:
5. Monitoring
- Daily monitoring of:
- Serum creatinine, BUN, electrolytes
- Fluid balance and urine output
- Vital signs 1
6. Determine AKI Etiology
Categorize AKI as:
- Prerenal: Volume depletion, heart failure, cirrhosis
- Intrinsic renal: Acute tubular necrosis, glomerulonephritis, interstitial nephritis
- Postrenal: Urinary tract obstruction 3
7. Specific Management Based on Etiology
- For prerenal AKI: Optimize volume status and cardiac output
- For intrinsic renal AKI: Treat underlying cause (e.g., antibiotics for infection)
- For postrenal AKI: Relieve obstruction (e.g., urinary catheterization, nephrostomy) 3
8. Nutrition Support
- Provide 20-30 kcal/kg/day total energy intake
- Protein recommendations:
- 0.8-1.0 g/kg/day in noncatabolic patients without dialysis
- 1.0-1.5 g/kg/day in patients on RRT
- Up to 1.7 g/kg/day in patients on CRRT and hypercatabolic patients 1
9. Consider Renal Replacement Therapy (RRT)
Indications for RRT:
- Refractory hyperkalemia
- Volume overload unresponsive to diuretics
- Severe metabolic acidosis
- Uremic symptoms (encephalopathy, pericarditis, pleuritis)
- Need to remove certain toxins 1
10. Nephrology Consultation
Consider nephrology referral for:
- All Stage 3 AKI patients
- AKI without clear cause
- Inadequate response to supportive treatment
- Preexisting stage 4 or higher CKD
- Need for RRT 1, 4
Important Considerations and Pitfalls
- AKI is not self-limited: Even one episode increases risk for CKD, cardiovascular disease, and death 5, 6
- Volume overload in AKI is associated with adverse outcomes; maintain careful fluid balance 6
- Avoid contrast media when possible in patients with AKI or at risk for AKI 1
- Team-based approaches for prevention, early diagnosis, and management improve outcomes 3
- Close follow-up is essential after AKI resolution, with serum creatinine monitoring every 2-4 days during hospitalization and every 2-4 weeks for 6 months after discharge 1
For patients with cirrhosis and AKI, the International Club of Ascites recommends diuretic withdrawal and plasma volume expansion with albumin (1 g/kg, maximum 100 g/day) for 2 consecutive days as initial management 2.