Management of Acute Kidney Injury (AKI)
AKI management centers on identifying and treating the underlying cause, optimizing hemodynamics with balanced crystalloids rather than saline, avoiding nephrotoxins, and initiating renal replacement therapy when specific life-threatening complications arise. 1, 2
Diagnosis and Staging
AKI is defined by:
- Serum creatinine increase ≥0.3 mg/dL within 48 hours, OR
- Serum creatinine increase ≥50% within 7 days, OR
- Oliguria (urine output criteria) 1
Initial workup must include:
- Serum creatinine and complete blood count
- Urinalysis with fractional excretion of sodium (FENa)
- Renal ultrasonography (especially in older men to exclude obstruction)
- Review medication list for nephrotoxins
- Assessment of intravascular volume status 3
Fluid Management and Hemodynamic Support
Use isotonic balanced crystalloids (lactated Ringer's or Plasma-Lyte) as first-line therapy for volume expansion rather than 0.9% saline or colloids. 2, 4 This recommendation is particularly strong given emerging evidence that balanced crystalloids reduce AKI incidence compared to saline (12% vs 22%, adjusted OR 0.50) 5.
Specific Fluid Recommendations:
- Avoid hydroxyethyl starch solutions entirely - they increase risk of renal failure, bleeding, and mortality in critically ill patients 4, 6
- Avoid albumin except in specific circumstances:
- Spontaneous bacterial peritonitis (prevents renal failure and death)
- Large-volume paracentesis in liver disease
- Hepatorenal syndrome diagnosis (after trial of albumin 1 g/kg/day up to 100 g/day) 2
- Use vasopressors in conjunction with fluids for vasomotor shock 2
The rationale for balanced crystalloids: Normal saline contains 154 mEq/L chloride (supraphysiologic), causing hyperchloremic metabolic acidosis, renal vasoconstriction, and inflammation. Balanced solutions have chloride content closer to plasma (98-110 mEq/L) with bicarbonate precursors (lactate or acetate), maintaining a strong ion difference of ~24 mEq/L 7, 8.
Nephrotoxin Management
Immediately discontinue or avoid:
- NSAIDs (cause both dysfunction and injury) 1
- Aminoglycosides (unless no alternative exists; use therapeutic drug monitoring if required) 2
- Contrast media when possible
- Other nephrotoxic medications 3
ACE inhibitors/ARBs: Hold during AKI episode, particularly in sepsis, surgery, or heart failure contexts. Timing of reinitiation requires clinical judgment based on recovery 1
Medications to AVOID
Do NOT use the following to prevent or treat AKI:
- Low-dose dopamine (Level 1A recommendation) 2
- Diuretics for prevention (Level 1B recommendation) - only use for volume overload management 2
- Fenoldopam 2
- Atrial natriuretic peptide 2
- Recombinant human IGF-1 2
Nutritional Support
- Target 20-30 kcal/kg/day total energy intake 2
- Do NOT restrict protein to delay dialysis 2
- Protein requirements:
- 0.8-1.0 g/kg/day in non-catabolic AKI without dialysis
- 1.0-1.5 g/kg/day in patients on RRT
- Up to 1.7 g/kg/day in hypercatabolic patients or those on CRRT 2
- Prefer enteral nutrition over parenteral 2
Renal Replacement Therapy (RRT) Indications
Initiate RRT for:
- Refractory hyperkalemia
- Volume overload unresponsive to diuretics
- Intractable metabolic acidosis
- Uremic complications: encephalopathy, pericarditis, or pleuritis
- Toxin removal (specific ingestions) 3
The optimal timing, dose, and modality remain areas of ongoing research 1.
Monitoring and Follow-up
After AKI resolution, patients require coordinated care with nephrology because they have:
- High risk of progressive CKD
- Increased mortality risk
- Risk of hypertension and volume overload
- Need for regular assessment of blood pressure, proteinuria, and metabolic parameters 4
What Are Balanced Crystalloids?
Balanced crystalloids are intravenous fluids with electrolyte composition closer to human plasma, containing physiologic chloride concentrations (98-110 mEq/L) and bicarbonate precursors (lactate or acetate), which prevent the hyperchloremic metabolic acidosis caused by normal saline. 7, 8
Composition Details:
Common balanced crystalloids include:
- Lactated Ringer's solution (contains lactate as bicarbonate precursor)
- Plasma-Lyte/Ringer's acetate (contains acetate and/or gluconate as bicarbonate precursors) 7, 8
Key compositional differences from 0.9% saline:
- Sodium: ~130-140 mEq/L (vs 154 mEq/L in saline)
- Chloride: 98-110 mEq/L (vs 154 mEq/L in saline)
- Potassium: 4-5 mEq/L (vs 0 in saline)
- Bicarbonate precursors: Present (vs absent in saline)
- Strong ion difference: ~24 mEq/L, matching plasma (vs 0 in saline) 8
Clinical Advantages:
Balanced crystalloids prevent:
- Hyperchloremic metabolic acidosis
- Renal vasoconstriction and inflammation
- Acute kidney injury (reduced incidence from 22% to 12%) 7, 5
Ringer's acetate is considered closest to ideal balance from both acid-base and tonicity perspectives, with minimal risk of acetate toxicity in volume loading scenarios 8. The growing evidence base, including large randomized trials showing reduced major adverse kidney events, supports preferential use of balanced crystalloids over saline in critically ill patients 7, 9, 5.