AKI Management Algorithm (Step-by-Step)
Step 1: Diagnose AKI
- Criteria:
- SCr increase ≥0.3 mg/dL within 48h or ≥1.5× baseline.
- Urine output <0.5 mL/kg/h for ≥6h.
- Rule out pseudorenal failure (e.g., dehydration, obstruction).
Step 2: Stage AKI (KDIGO)
|
Stage |
SCr Criteria |
Urine Output Criteria |
|
1 |
≥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 |
<0.3 mL/kg/h for ≥24h or anuria |
Step 3: Identify the Cause
Prerenal (60%)
- History/Exam: Hypotension, dehydration, heart failure.
- Labs: FeNa <1%, urine osmolality >500 mOsm/kg.
- Management: Fluid resuscitation, optimize hemodynamics.
Intrinsic (35%)
- ATN: Acute Tubular Necrosis: Ischemia, toxins (aminoglycosides, contrast).
- Labs: FeNa >2%, granular casts.
- Management: Discontinue nephrotoxins, supportive care.
- AIN: Acute interstitial nephritis: Drugs (penicillin, PPIs, NSAIDs).
- Labs: Eosinophils in urine, rash, fever.
- Management: Stop offending drugs, ± steroids.
- Glomerulonephritis/Vasculitis:
- Labs: Proteinuria, hematuria, low C3/C4.
- Management: Immunosuppression (steroids, cyclophosphamide).
Postrenal (5%)
- History/Exam: Obstruction (stones, BPH, tumors).
- Imaging: Renal ultrasound (hydronephrosis).
- Management: Catheterization, nephrostomy, or stenting.
Step 4: Immediate Management
- For All AKI:
- Discontinue nephrotoxins (NSAIDs, ACEi/ARBs, aminoglycosides).
- Optimize hemodynamics (fluids, vasopressors if needed).
- Monitor:
- SCr, BUN, electrolytes (K⁺, Na⁺, Ca²⁺, PO₄³⁻).
- Urine output (Foley catheter if oliguric).
- Fluid balance (strict I/O).
- Correct Electrolyte Imbalances:
- Hyperkalemia (K⁺ >6.5 mEq/L):
- Calcium gluconate (10 mL IV over 10 min).
- Insulin + glucose (10 units insulin + 50 mL D50).
- Albuterol nebulization (10–20 mg).
- Dialysis if refractory or ECG changes.
- Metabolic acidosis (pH <7.1): Bicarbonate.
- Fluid overload: Diuretics (if responsive) or RRT.
Step 5: Indications for RRT (Dialysis)
Start RRT if AEIOU criteria are met:
- Acidosis (pH <7.1, refractory).
- Electrolyte disturbances (K⁺ >6.5 mEq/L, refractory).
- Intoxication (dialyzable toxins: lithium, methanol, ethylene glycol).
- Overload (fluid overload refractory to diuretics).
- Uremia (BUN >100 mg/dL, pericarditis, encephalopathy, bleeding).
Modality Choice:
- Intermittent Hemodialysis (IHD): Stable patients.
- Continuous RRT (CRRT): Hemodynamically unstable (ICU).
- Peritoneal Dialysis (PD): If vascular access is difficult.
Step 6: Supportive Care
- Nutrition:
- Protein: 0.8–1.0 g/kg/day.
- Calories: 25–30 kcal/kg/day.
- Fluid Balance:
- Restrict fluids if oliguric (insensible losses + urine output).
- Infection Prophylaxis:
- Adjust antibiotic doses for renal function.
Step 7: Monitor and Follow-Up
- Daily:
- SCr, BUN, electrolytes, urine output, weight, fluid balance.
- Renal Ultrasound: If no improvement in 24–48h (rule out obstruction).
- Nephrology Consult:
- Stage 2–3 AKI.
- Unclear etiology.
- Need for RRT.
Step 8: Prognosis and Prevention
- Prognosis:
- Mortality: ~10–30% (higher in ICU, sepsis, Stage 3).
- Recovery: Prerenal AKI often reversible; ATN may take weeks.
- ~20–30% progress to CKD.
- Prevention:
- Avoid nephrotoxins.
- Hydrate before contrast procedures.
- Optimize hemodynamics in high-risk patients.
Quick Reference Table: AKI Causes and Management
|
Type |
Causes |
Diagnostic Clues |
Management |
|
Pre-renal |
Hypovolemia, hypotension, HF |
FeNa <1%, urine osmolality >500 |
Fluids, optimize hemodynamics |
|
ATN |
Ischemia, toxins (aminoglycosides) |
FeNa >2%, granular casts |
Discontinue nephrotoxins, supportive |
|
AIN |
Drugs (penicillin, PPIs, NSAIDs) |
Eosinophils in urine, rash, fever |
Stop drug, ± steroids |
|
Glomerulonephritis |
Immune-mediated (e.g., vasculitis) |
Proteinuria, hematuria, low C3/C4 |
Immunosuppression (steroids, cyclophosphamide) |
|
Post-renal |
Obstruction (stones, BPH, tumors) |
Hydronephrosis on ultrasound |
Catheterization, nephrostomy, stenting |
