Acute Kidney Injury

 AKI Management Algorithm (Step-by-Step)

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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).

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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