1. Types of AKI in the ICU

A. Pre-renal (most common)

• Septic shock

• Volume depletion

• Third-spacing

• Cardiorenal syndrome

Clues: BUN:Cr > 20, FeNa < 1%, FeUrea < 35% (esp. if on diuretics)

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B. Intrinsic AKI

• ATN (ischemia, sepsis, nephrotoxins) — MOST common intrinsic

• AIN (antibiotics, PPIs)

• Glomerulonephritis

• Rhabdomyolysis

• Tumor lysis syndrome

• Contrast nephropathy

Clues: muddy brown casts, FeNa > 2%, rising creatinine despite fluids

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C. Post-renal

• Foley obstruction

• Ureteral obstruction (stones, tumor)

• Prostatic obstruction

Clue: HYDRONEPHROSIS on renal ultrasound

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2. Initial ICU Evaluation (FAST)

A. Examine the patient

• Volume status: JVP, edema, lungs

• Foley catheter patency

• Output: oliguria = <0.5 mL/kg/hr

B. Labs

• CMP (BUN, Cr, electrolytes)

• ABG

• CK (if rhabdo)

• Urinalysis + microscopy

• FeNa or FeUrea

• Lactate

C. Imaging

• Renal ultrasound (avoid CT unless needed)

D. Medications

• Stop nephrotoxins:

  • NSAIDs

  • ACE/ARB

  • Vancomycin + Zosyn (avoid combo if possible)

  • IV contrast if avoidable

  • Aminoglycosides

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🟡 3. Fluid Management (Critical in ICU)

If hypovolemic:

• Crystalloids: balanced fluids preferred (LR, PlasmaLyte)

• Avoid large NS boluses → hyperchloremic acidosis → worsen AKI

If fluid overloaded:

• Diuretic trial: Furosemide 40–80 mg IV, or drip

• Add thiazide (metolazone) if resistant

• Consider early CRRT if:

  • Severe overload

  • Respiratory compromise

  • Inability to diurese

Golden rule:

💡 Don’t give fluids to a wet patient. Don’t give diuretics to a dry patient.

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🔴 4. Electrolyte Emergencies (ICU MUST-KNOW)

A. Hyperkalemia (K > 6 or EKG changes)

1. Stabilize myocardium
✔ Calcium gluconate 1 g IV

2. Shift K intracellularly
✔ Insulin 10 units IV + D50
✔ Albuterol neb
✔ Sodium bicarb (metabolic acidosis)

3. Remove K from body
✔ Loop diuretics
✔ Lokelma / Kayexalate
✔ Dialysis if refractory or life-threatening

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B. Severe Acidosis

pH < 7.20

• Treat cause

• Bicarbonate drip if severe and HCO₃ < 10

• Consider dialysis if unresponsive

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C. Hyponatremia / Hypernatremia

• Correct slowly

• Hyponatremia: 4–6 mEq/L per 24 hrs max

• Hypernatremia: free water (enteral or hypotonic fluids)

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D. Hyperphosphatemia

• Common in AKI

• Use phosphate binders (sevelamer)

• Dialysis if severe

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🟢 5. Indications for Dialysis (AEIOU)

Classic ICU mnemonic:

A – Acidosis

• pH < 7.1

• Refractory to medical therapy

E – Electrolytes

• Hyperkalemia > 6.5 or EKG changes

• Refractory to therapy

I – Intoxication

• Ethylene glycol

• Methanol

• Lithium

• Salicylates

• Valproate

• Theophylline

O – Overload

• Pulmonary edema unresponsive to diuretics

U – Uremia

• Encephalopathy

• Pericarditis

• Bleeding due to platelet dysfunction

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🔵 6. CRRT vs iHD vs SLED

A. CRRT (Continuous Renal Replacement Therapy)

Indications in ICU:

• Hemodynamic instability

• Severe fluid overload

• Severe acidosis

• Very high catabolic states

Pros: gentle, 24h, stable hemodynamics
Cons: requires ICU nursing, anticoagulation

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B. Intermittent Hemodialysis (iHD)

Indications:

• Hemodynamically stable patients

• Standard AKI/CKD dialysis

Pros: fast solute removal
Cons: risk of hypotension

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C. SLED (Slow-Low Efficiency Dialysis)

• Hybrid between CRRT and iHD

• Useful in borderline unstable ICU patients

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🟣 7. Medication Dosing in Renal Failure

Always adjust:

• Vancomycin

• Zosyn

• Meropenem (extend infusion)

• Opioids (avoid morphine → metabolites accumulate)

• Gabapentin

• Metformin (avoid in AKI)

• DOACs

• Insulin needs decrease as renal function worsens → risk of hypoglycemia

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🔥 ICU PEARLS FOR RENAL FAILURE

• AKI in sepsis often improves after MAP > 65 and adequate perfusion

• Over-resuscitation worsens lung function in ARDS patients

• Vancomycin + Zosyn dramatically increases AKI risk—avoid combination if possible

• Use urine microscopy — muddy brown casts suggest ATN

• Start CRRT early in severe shock or severe fluid overload

• Check daily weights, strict I/O, bladder scans

• Remember FeUrea < 35% is reliable even when on diuretics

• High-dose loop diuretics may cause ototoxicity (rare)