Management of Acute Kidney Injury
Immediately identify and discontinue all nephrotoxic medications, optimize volume status with balanced crystalloids, and initiate continuous monitoring of serum creatinine and urine output to prevent progression to higher AKI stages, which independently increases mortality risk.
Diagnosis and Staging
Use KDIGO criteria to confirm AKI: a rise in serum creatinine ≥0.3 mg/dL within 48 hours, or ≥50% increase within 7 days, or urine output <0.5 mL/kg/h for ≥6 hours 1.
Stage AKI immediately according to KDIGO 1:
- Stage 1: Creatinine 1.5-1.9× baseline or ≥0.3 mg/dL rise, or urine output <0.5 mL/kg/h for 6-12 hours
- Stage 2: Creatinine 2.0-2.9× baseline, or urine output <0.5 mL/kg/h for ≥12 hours
- Stage 3: Creatinine ≥3× baseline or ≥4.0 mg/dL with acute rise ≥0.3 mg/dL, initiation of RRT, or urine output <0.3 mL/kg/h for ≥24 hours (or anuria ≥12 hours)
Obtain baseline serum creatinine from the prior 3 months when available; if unavailable, use admission creatinine while acknowledging potential under-diagnosis of community-acquired AKI 1.
Etiology Evaluation
Screen for nephrotoxic exposures including NSAIDs, ACE inhibitors/ARBs, aminoglycosides, iodinated contrast, and chemotherapy agents 12.
Perform urinalysis with microscopy to identify dysmorphic red blood cells, red-cell casts, and proteinuria suggesting glomerulonephritis 1.
Order autoimmune serologies when glomerulonephritis or vasculitis is suspected: antinuclear antibody, anti-dsDNA, ANCA panel, and anti-GBM antibodies 1.
Obtain renal ultrasonography in patients with risk factors for postrenal obstruction (older males with prostatic hypertrophy, pelvic malignancy, single kidney) 34.
Immediate Nephrotoxin Management
Discontinue all identified nephrotoxic agents immediately, particularly NSAIDs and aminoglycosides 12. This is critical because nephrotoxic drugs account for 20-25% of AKI cases 1.
Hold ACE inhibitors and ARBs during acute AKI; resume only after renal function stabilizes and volume status is optimized 12. The timing of discontinuation and re-initiation remains an area requiring further study in different clinical contexts 5.
Adjust all medication dosing according to current renal function to prevent drug accumulation and further injury 12.
Avoid the "triple whammy" combination of NSAIDs, diuretics, and ACE inhibitors/ARBs, which creates pharmacodynamic interactions that dramatically increase AKI risk 2.
Fluid Management and Hemodynamic Support
Use balanced crystalloid solutions (lactated Ringer's or Plasma-Lyte) rather than 0.9% saline for volume resuscitation, as balanced fluids are associated with lower risk of worsening AKI 15.
Avoid inappropriate fluid administration in established AKI, as attempts to "reverse" established injury result in fluid overload and a vicious cycle of worsening kidney function 555.
Recognize that oliguria has multiple etiologies beyond hypovolemia; do not reflexively administer fluids for oliguria without assessing volume status 555.
Monitor for fluid overload, which independently raises mortality risk and worsens creatinine distribution 1. The optimal methods for detecting fluid overload and guiding fluid removal remain areas of active investigation 55.
Monitoring and Progression Prevention
Perform serial serum creatinine measurements at intervals appropriate to AKI stage to track progression or recovery 1. Direct creatinine trends are preferred over eGFR calculations, which are unreliable in acute settings 1.
Recognize that progression to higher AKI stages is strongly associated with increased mortality; vigilant monitoring is essential 1.
Define recovery as regression to a lower stage or return of serum creatinine to within 0.3 mg/dL of baseline 1.
When creatinine is unavailable, urine output criteria alone suffice for AKI diagnosis 1.
Renal Replacement Therapy Indications
Initiate RRT emergently for life-threatening complications 55:
- Refractory hyperkalemia
- Severe volume overload unresponsive to diuretics
- Intractable metabolic acidosis
- Uremic encephalopathy, pericarditis, or pleuritis
- Certain toxin removal
In hemodynamically unstable patients, use continuous RRT rather than intermittent hemodialysis, as it is more physiologically appropriate despite lack of RCT evidence showing superior outcomes 5.
Deliver adequate RRT dosing 5:
- Intermittent/extended RRT: Kt/V ≥1.2 per treatment, 3 times weekly
- Continuous RRT: Effluent volume 20-25 mL/kg/h
- Peritoneal dialysis: 0.3 Kt/V per session
Use regional citrate anticoagulation for continuous RRT in patients without contraindications 5.
Discontinue RRT when kidney function has recovered or when RRT becomes inconsistent with shared care goals 5.
Vascular Access for RRT
Use an uncuffed non-tunneled dialysis catheter of appropriate length and gauge to initiate RRT 5.
First choice for catheter site is right internal jugular vein or femoral vein (femoral is inferior in patients with increased body mass); next choices are left jugular vein then subclavian vein 5.
Consider a cuffed catheter in patients with expected prolonged RRT indication 5.
Nephrology Consultation Criteria
Consult nephrology for 3:
- Inadequate response to supportive treatment
- AKI without clear cause
- Stage 3 or higher AKI
- Preexisting stage 4 or higher chronic kidney disease
- Need for renal replacement therapy
- Suspected glomerulonephritis requiring biopsy
Perform kidney biopsy when AKI persists beyond 7-10 days without clear cause or when glomerulonephritis is suspected 1.
Common Pitfalls to Avoid
Do not use biomarker-positive states alone as indication for volume replacement; presence of early renal injury does not automatically signify need for fluids 555.
Avoid aggressive fluid resuscitation in established AKI, which leads to fluid overload and worsening outcomes 555.
Do not rely on eGFR in acute settings; it is unreliable during rapid changes in kidney function 1.
Recognize that 25% of non-critically ill patients receiving three or more nephrotoxins develop AKI; systematic screening and discontinuation is essential 2.