• Nephrology · Critical Care
Acute Kidney Injury (AKI)
KDIGO Staging · Causes (Pre/Renal/Post) · Fluid Management · Dialysis Criteria · Nephrotoxin Avoidance
🔬 KDIGO Staging (Kidney Disease: Improving Global Outcomes 2012)
StageSerum Creatinine CriteriaUrine Output CriteriaAction
Stage 1 Rise ≥0.3 mg/dL within 48h or 1.5–1.9× baseline within 7d <0.5 mL/kg/h for 6–12h Identify + remove cause; optimize fluids; stop nephrotoxins
Stage 2 Cr rise 2.0–2.9× baseline within 7 days <0.5 mL/kg/h for ≥12h All Stage 1 measures + nephrology consult; assess for RRT
Stage 3 Cr rise ≥3× baseline or Cr ≥4.0 mg/dL or RRT initiation or eGFR <35 (<18y) <0.3 mL/kg/h for ≥24h or anuria ≥12h Urgent nephrology; prepare RRT; ICU admission
AKI Definition (any 1 criterion): sCr rise ≥0.3 mg/dL within 48h · sCr rise ≥1.5× baseline within 7d · UO <0.5 mL/kg/h for ≥6h
🔎 Causes of AKI
Pre-Renal (~60%)
Hypovolemia (bleeding, GI losses, burns)
Reduced cardiac output (HF, cardiogenic shock)
Sepsis / distributive shock
Hepatorenal syndrome
NSAIDs, ACEi/ARBs (afferent dilation block)
FENa <1%; UNa <20 mEq/L; responds to fluids
Intrinsic Renal (~35%)
ATN: ischemic (shock) or nephrotoxic (contrast, gentamicin, vancomycin)
Glomerulonephritis (rapidly progressive)
Interstitial nephritis (drug-induced: NSAIDs, PPIs, β-lactams)
Vascular: TTP/HUS, renal artery occlusion
Myoglobinuria (rhabdomyolysis)
FENa >2%; muddy brown casts on UA
Post-Renal (~5%)
BPH / prostatic obstruction (most common in Gulf elderly males)
Ureteric stones (bilateral or solitary kidney)
Cervical / pelvic malignancy
Bladder outlet obstruction
Retroperitoneal fibrosis
Renal US: hydronephrosis; foley → immediate relief
💧 Fluid & General Management
Pre-renal: Fluid challenge — 500 mL crystalloid bolus; reassess UO
Target MAP ≥65 mmHg (or higher in CKD/HTN)
Avoid fluid overload — use dynamic assessment (PLR, IVC)
Hold ACEi/ARBs/NSAIDs/metformin
Contrast avoidance; if unavoidable: pre-hydrate with 0.9% NaCl
Nutritional support: protein 0.8–1.0 g/kg/day (non-catabolic AKI)
Monitor strict I&O; daily weights; electrolytes q4–8h
Urinary catheter for accurate monitoring in Stage 2–3
🔴 RRT Indications (AKI Dialysis)
●A — Metabolic Acidosis: pH <7.1 refractory to treatment
●E — Electrolytes: K⁺ >6.5 mEq/L or rapidly rising despite treatment
●I — Intoxication: dialyzable toxins (salicylates, methanol, lithium)
●O — Overload: fluid overload unresponsive to diuretics, pulmonary edema
●U — Uremia: encephalopathy, pericarditis, bleeding (BUN >100 mg/dL)
CRRT preferred in hemodynamically unstable patients. IHD for stable patients.
⚠️ Nephrotoxin Avoidance & Dose Adjustment
●NSAIDs: Contraindicated in AKI — prostaglandin inhibition → afferent constriction
●Aminoglycosides (gentamicin): Avoid if possible; once-daily dosing; monitor troughs
●Iodinated contrast: Minimize dose; pre/post-hydration; avoid NSAID same day
●Vancomycin: AUC-based monitoring (AUC/MIC 400–600); avoid with piperacillin
●ACEi/ARBs: Stop in AKI — reduce GFR by inhibiting efferent tone
●Metformin: Stop when eGFR <30 — risk of lactic acidosis
CCM Notes · FOAMed · Critical Care Clinical Reference
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Based on KDIGO AKI Guidelines 2012 / 2024 Update
Educational use only