Initial Management of Acute Kidney Injury
The initial management of acute kidney injury (AKI) should focus on discontinuing nephrotoxic medications, assessing volume status, providing appropriate fluid resuscitation, and identifying and treating the underlying cause. 1
Diagnosis and Classification
AKI is defined by:
- Increase in serum creatinine ≥0.3 mg/dL within 48 hours
- Increase in serum creatinine ≥50% from baseline within 7 days
- Urine output <0.5 mL/kg/h for >6 hours
KDIGO staging system:
| Stage | Serum Creatinine | Urine Output |
|---|---|---|
| 1 | 1.5-1.9× baseline or ≥0.3 mg/dL increase | <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 |
Immediate Management Steps
Discontinue nephrotoxic medications
Volume status assessment and management
- Clinical examination: vital signs, jugular venous distension, edema, weight changes 1
- Laboratory evaluation: BUN/creatinine ratio, urine sodium, fractional excretion of sodium (FENa)
- For hypovolemia: Administer balanced crystalloids (Lactated Ringer's or PlasmaLyte) 1
- Initial bolus: 500-1000 mL given rapidly
- Normal saline is acceptable but limit to 1-1.5 L to avoid hyperchloremic acidosis
- For hypervolemia: Consider diuretics or renal replacement therapy if severe 2
Diagnostic workup
- Urinalysis and urine microscopy to evaluate for hematuria, proteinuria, casts
- Renal ultrasound to rule out obstruction (especially in older males) 1
- Blood tests: complete blood count, comprehensive metabolic panel, urine chemistries
Identify and treat underlying cause
- Prerenal: Restore effective circulating volume
- Intrinsic: Treat specific cause (e.g., antibiotics for infection)
- Postrenal: Relieve obstruction if present
Management Based on Etiology
Prerenal AKI
- Fluid resuscitation with balanced crystalloids 1
- In patients with cirrhosis, consider albumin 1 g/kg/day for 2 days if serum creatinine shows doubling from baseline 2
- Monitor for fluid overload, especially when administering albumin (risk of pulmonary edema) 2
Intrinsic AKI
- Treat underlying cause (e.g., antibiotics for infection)
- Supportive care to maintain kidney function
- Consider nephrology consultation for severe cases (Stage 3 AKI) 1
Postrenal AKI
- Relieve obstruction (e.g., urinary catheter for bladder outlet obstruction)
- Urological consultation for definitive management
Special Considerations
Patients with Cirrhosis
- Hold diuretics, beta-blockers, and nephrotoxic drugs 2
- Treat infections and other precipitating causes 2
- For suspected HRS-AKI unresponsive to volume expansion:
- Albumin 1 g/kg IV on day 1, then 20-40 g daily
- Consider vasoactive agents (terlipressin, octreotide/midodrine, or norepinephrine) 2
Nutritional Support
- Provide 20-30 kcal/kg/day total energy intake
- Protein intake of 0.8-1.0 g/kg/day in noncatabolic patients without dialysis 1
- Prefer enteral nutrition when possible 1
Indications for Renal Replacement Therapy
Consider RRT when:
- Severe metabolic acidosis persists
- Hyperkalemia is refractory to medical management
- Volume overload remains unresponsive to conservative measures
- Uremic symptoms develop (encephalopathy, pericarditis, pleuritis) 1
Monitoring and Follow-up
- Monitor urine output, serum creatinine, electrolytes
- Follow patients who recover from AKI closely:
- Serum creatinine every 2-4 days during hospitalization
- Every 2-4 weeks for 6 months after discharge 1
- Refer to nephrology for:
- All Stage 3 AKI patients
- AKI without clear cause
- Inadequate response to supportive treatment
- Preexisting stage 4 or higher CKD 1
Prevention of AKI
- Avoid nephrotoxic medications when possible
- Adjust medication doses based on renal function
- Maintain adequate hydration, especially before contrast procedures
- Implement pharmacist-led quality-improvement programs to reduce nephrotoxic exposures in hospital settings
The key to successful management of AKI is early recognition, prompt intervention, and addressing the underlying cause while providing appropriate supportive care to prevent further kidney damage.