Laboratory Values Indicating Acute Kidney Injury
Acute kidney injury is diagnosed when serum creatinine increases by ≥0.3 mg/dL (≥26.5 µmol/L) within 48 hours OR increases to ≥1.5 times baseline within 7 days OR when urine output falls below 0.5 mL/kg/h for more than 6 hours. 1, 2
Diagnostic Criteria
The KDIGO criteria provide the current standard for AKI diagnosis 1:
Baseline Creatinine Determination:
- Use serum creatinine from the previous 3 months when available (closest value to admission) 3
- If unavailable, use admission creatinine as baseline 3
- Do NOT use estimated creatinine from MDRD formula in cirrhotic patients—it's inaccurate 3
AKI Staging (determines treatment intensity) 1:
- Stage 1: Creatinine rise ≥0.3 mg/dL within 48h OR 1.5-1.99× baseline within 7 days OR urine output <0.5 mL/kg/h for >6h
- Stage 2: Creatinine 2.0-2.99× baseline OR urine output <0.5 mL/kg/h for >12h
- Stage 3: Creatinine ≥3× baseline OR ≥4.0 mg/dL (353.6 µmol/L) with acute rise ≥0.3 mg/dL OR urine output <0.3 mL/kg/h for 24h OR anuria for 12h OR initiation of dialysis
Treatment Algorithm
Immediate Actions for ALL Stages 3, 2:
- Stop nephrotoxic agents immediately: NSAIDs, ACE inhibitors/ARBs, diuretics, aminoglycosides, contrast media 2
- Search rigorously for infection: Diagnostic paracentesis (if ascites present), blood cultures, urine cultures, chest X-ray 2
- Assess volume status: Physical exam, vital signs, consider echocardiography or CVP if central line present 2
Stage 1 AKI Management 3:
First-line treatment:
- Withdraw diuretics and nephrotoxic drugs 3
- Plasma volume expansion with crystalloids, albumin, or blood if hypovolemia suspected 3
- Monitor closely for progression 3
If no response (creatinine remains >2× baseline):
Stage 2-3 AKI Management 2:
When creatinine doubles from baseline despite initial measures, initiate HRS-AKI treatment:
Albumin + Vasoconstrictor therapy 2:
- Albumin: 1 g/kg IV day 1, then 20-40 g daily 2
- Continue until creatinine returns to within 0.3 mg/dL of baseline for 2 consecutive days OR maximum 14 days 2
Vasoconstrictor options (in order of preference):
Terlipressin (first-line if available) 2:
Octreotide + Midodrine (if terlipressin unavailable) 2:
- Midodrine: Start 7.5 mg PO, titrate to 12.5 mg three times daily
- Octreotide: Start 100 mcg SC, titrate to 200 mcg three times daily 2
Norepinephrine (ICU setting) 2:
- Start 0.5 mg/h continuous IV infusion
- Increase by 0.5 mg/h every 4 hours to maximum 3 mg/h
- Goal: Increase MAP ≥10 mmHg AND/OR urine output >50 mL/h for ≥4 hours 2
Critical Caveats
Serum creatinine limitations in cirrhosis 3, 2:
- Underestimates true kidney dysfunction due to reduced muscle mass, decreased hepatic creatine synthesis, volume overload dilution, and bilirubin interference with assays 3, 2
- A "normal" creatinine may represent significant GFR reduction 3
Volume status assessment is crucial 2:
- Overaggressive diuresis causes prerenal AKI (most common cause in cirrhosis) 2
- Excessive fluid administration risks pulmonary edema 2
- Use clinical exam, urine sodium (<20 mEq/L suggests prerenal), and fractional excretion of sodium (<1% suggests prerenal) 4, 5
Renal replacement therapy indications 5:
- Refractory hyperkalemia
- Volume overload unresponsive to diuretics
- Intractable acidosis
- Uremic complications (encephalopathy, pericarditis, pleuritis)
- Certain toxin removal
Prevention is paramount 2:
- Avoid NSAIDs completely
- Avoid large-volume paracentesis without albumin replacement (8g albumin per liter removed)
- Monitor diuretics carefully—hold if creatinine rising
- Consider holding non-selective beta-blockers during acute illness 2