Part of the ICU Emergencies Hub — browse every related guide in one place.
KDIGO AKI staging, prerenal vs intrinsic vs postrenal classification, FENa interpretation, CKD staging, uremic symptoms, electrolyte management, and dialysis indications.
| Stage | Serum Creatinine | Urine Output |
|---|---|---|
| Stage 1 | Rise ≥0.3 mg/dL within 48h OR 1.5–1.9× baseline within 7 days | <0.5 mL/kg/hr for 6–12 hours |
| Stage 2 | 2.0–2.9× baseline | <0.5 mL/kg/hr for ≥12 hours |
| Stage 3 | ≥3.0× baseline OR ≥4.0 mg/dL OR initiation of RRT | <0.3 mL/kg/hr for ≥24h OR anuria ≥12h |
| Category | Causes | BUN/Cr Ratio | FENa | Urine Osmolality | Key Feature |
|---|---|---|---|---|---|
| Prerenal (decreased perfusion) | Hypovolemia (dehydration, hemorrhage, burns), CHF, hepatorenal syndrome, sepsis, NSAIDs, ACE inhibitors | >20:1 (BUN disproportionately high) | <1% | >500 mOsm/kg (concentrated — kidneys trying to hold water) | Kidneys intact but underperfused; responds to fluids |
| Intrinsic/Intrarenal | ATN (most common: ischemia, nephrotoxins — aminoglycosides, contrast, myoglobin); glomerulonephritis; interstitial nephritis (medications) | <20:1 | >2% (damaged tubules can't reabsorb Na) | <350 mOsm/kg (isosthenuria — kidneys losing concentrating ability) | Muddy brown casts (ATN); RBC casts (GN); WBC casts (interstitial nephritis) |
| Postrenal (obstruction) | BPH, prostate cancer, cervical cancer, bilateral ureteral stones, foley kinked/blocked, neurogenic bladder | Variable | Variable | Variable | Anuria more common; bilateral obstruction required for AKI (one functional kidney enough); bladder scan first |
| Category | Examples | Nursing Action |
|---|---|---|
| Aminoglycosides | Gentamicin, tobramycin, amikacin | Trough-based dosing or extended-interval dosing; monitor Cr daily; hydrate well; avoid with other nephrotoxins |
| IV Contrast (iodinated) | CT contrast, angiography dye | Pre-hydrate with IV NS; consider N-acetylcysteine; hold metformin 48h post-contrast; avoid in Cr >1.5–2.0 or GFR <30–45 |
| NSAIDs | Ibuprofen, naproxen, ketorolac | Avoid in AKI, hypovolemia, elderly, CKD, CHF, cirrhosis; afferent arteriole prostaglandin-dependent in these patients |
| ACE inhibitors/ARBs | Lisinopril, losartan | Hold in acute AKI and hypovolemia; efferent arteriole dilation → drops GFR when perfusion low; restart when stable |
| Myoglobin (rhabdomyolysis) | Crush injury, severe exercise, statin toxicity, malignant hyperthermia | Aggressive IV fluids (target UO >200 mL/hr until urine clears); sodium bicarbonate (alkalinize urine); CK levels; tea-colored urine; troponin may be falsely elevated |
| Vancomycin | IV vancomycin | AUC-based dosing preferred over trough only (AUC 400–600 mg·h/L); monitor Cr and troughs; avoid concurrent nephrotoxins |
| Stage | GFR (mL/min/1.73m²) | Description | Key Management |
|---|---|---|---|
| G1 | ≥90 | Normal GFR + kidney damage markers (proteinuria, hematuria) | Treat underlying cause; BP control; RAAS blockade if proteinuria |
| G2 | 60–89 | Mildly decreased | Monitor; cardiovascular risk reduction |
| G3a | 45–59 | Mild-moderate decrease | Avoid nephrotoxins; adjust drug doses; anemia of CKD begins; phosphate restriction |
| G3b | 30–44 | Moderate-severe decrease | Nephrology referral; EPO/ESA for anemia; vitamin D supplementation; dietary restrictions |
| G4 | 15–29 | Severely decreased | Prepare for renal replacement therapy; AV fistula planning (created now — takes 4–6 weeks to mature) |
| G5 (ESRD) | <15 (or dialysis) | Kidney failure | Dialysis or transplant |
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