Initial Approach to Managing Acute Kidney Injury
The initial approach to managing acute kidney injury (AKI) should include immediate discontinuation of nephrotoxic medications, appropriate fluid management with isotonic crystalloids (preferably balanced solutions), medication dose adjustments based on GFR, and daily monitoring of renal function, electrolytes, and fluid balance. 1
Assessment and Diagnosis
Definition and Staging
- Use KDIGO criteria to diagnose and stage AKI:
Stage Serum Creatinine Urine Output 1 Increase ≥0.3 mg/dL within 48h 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 1
Initial Evaluation
Determine the cause of AKI by categorizing as:
- Prerenal: Inadequate renal perfusion (dehydration, hypotension, heart failure)
- Intrinsic renal: Direct kidney damage (ATN, glomerulonephritis, interstitial nephritis)
- Postrenal: Urinary tract obstruction
Laboratory workup:
- Serum creatinine and BUN
- Complete blood count
- Urinalysis
- Electrolytes
- Fractional excretion of sodium (FENa)
- Urine microscopy to identify casts, cells, or crystals 1
Imaging:
- Renal ultrasonography to rule out obstruction (especially important in older men) 1
Management Priorities
1. Medication Management
Immediately discontinue nephrotoxic medications:
- NSAIDs
- ACE inhibitors and ARBs
- Aminoglycosides (if possible)
- Other nephrotoxic agents 1
Adjust medication doses based on estimated GFR 1
2. Fluid Management
Assess volume status carefully:
- Use physical examination findings (skin turgor, mucous membranes, jugular venous pressure)
- Consider central venous pressure monitoring in hemodynamically unstable patients 1
For hypovolemic patients:
- Administer isotonic crystalloids (balanced solutions preferred over normal saline)
- Use goal-directed fluid therapy to optimize hemodynamics 1
For euvolemic or hypervolemic patients:
- Restrict fluid intake as needed
- Consider diuretics if volume overloaded 1
3. Nutritional 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 renal replacement therapy
- Up to 1.7 g/kg/day in patients on continuous RRT and hypercatabolic patients
- Prefer enteral nutrition when possible 1
4. Monitoring
- Daily monitoring of:
- Vital signs
- Serum creatinine and BUN
- Electrolytes (especially potassium)
- Fluid balance
- Urine output 1
Indications for Renal Replacement Therapy
Consider renal replacement therapy 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
For hemodynamically unstable patients, continuous renal replacement therapy (CRRT) is preferred over intermittent hemodialysis 1
Follow-up Care
- Monitor serum creatinine every 2-4 days during hospitalization
- After discharge, check serum creatinine every 2-4 weeks for 6 months 1
- Refer to nephrology based on AKI severity:
- All Stage 3 AKI patients require nephrology consultation
- Stage 1-2 with risk factors for progression should also be referred 1
Common Pitfalls to Avoid
- Delayed recognition: Even mild AKI increases risk of mortality and progression to chronic kidney disease
- Inadequate volume assessment: Both under-resuscitation and fluid overload can worsen AKI
- Continued use of nephrotoxic medications: Review all medications daily
- Failure to identify and treat the underlying cause: Address the primary etiology of AKI
- Inadequate follow-up: AKI increases long-term risk of cardiovascular disease, chronic kidney disease, and death 1
By following this structured approach to AKI management, focusing on early identification, prompt intervention, and appropriate follow-up, outcomes can be significantly improved.