Critical Care · Year 4 · from Critical Care
Case 1: Sepsis-Associated AKI with Hyperkalemia
Clinical Image
Source: Wikimedia Commons - ECG in Hyperkalemia - CC BY-SA 3.0
Case Presentation
A 58-year-old man with type 2 diabetes mellitus is admitted to the ICU with septic shock secondary to a diabetic foot infection. His baseline creatinine is 1.2 mg/dL. On ICU day 2, despite adequate fluid resuscitation and vasopressor support achieving MAP greater than 65 mmHg, his creatinine rises to 3.8 mg/dL with urine output declining to 15 mL/hour (0.2 mL/kg/hr). Urinalysis shows muddy brown casts consistent with acute tubular necrosis. He meets KDIGO Stage 3 AKI criteria (creatinine greater than 3 times baseline). Review of his medications reveals recent aminoglycoside (gentamicin) and vancomycin exposure; vancomycin trough was 24 mcg/mL (supratherapeutic). Both nephrotoxins are discontinued and alternatives substituted. On day 3, morning labs reveal potassium of 6.8 mEq/L. ECG shows peaked T waves and widened QRS complexes (QRS 140 ms, baseline 90 ms). He receives immediate treatment: calcium gluconate 1g IV for cardiac membrane stabilization, regular insulin 10 units IV with D50 50 mL for intracellular potassium shift, and sodium polystyrene sulfonate 30g orally for potassium elimination. Repeat potassium 2 hours later is 5.9 mEq/L with improved ECG. Given his oliguric AKI with refractory hyperkalemia and developing metabolic acidosis (pH 7.22, bicarbonate 14 mEq/L), the decision is made to initiate continuous renal replacement therapy (CRRT). A dialysis catheter is placed in the right internal jugular vein, and CVVHDF is initiated with regional citrate anticoagulation. Over the following week, his sepsis resolves, and his kidney function gradually recovers. CRRT is discontinued on day 8, and he is discharged with creatinine of 1.8 mg/dL with plan for nephrology follow-up.
Key Learning Points
- KDIGO AKI staging: Stage 1 (Cr 1.5-1.9x baseline or increase greater than 0.3 mg/dL), Stage 2 (Cr 2-2.9x baseline), Stage 3 (Cr greater than 3x baseline or greater than 4 mg/dL or RRT initiation)
- Hyperkalemia with ECG changes (peaked T waves, widened QRS, loss of P waves) is a medical emergency requiring immediate treatment: calcium for cardioprotection, insulin/glucose for shifting, binders for elimination
- Indications for RRT in AKI are summarized by AEIOU: Acidosis (refractory), Electrolytes (hyperkalemia with ECG changes), Intoxication, Overload (volume), Uremia (encephalopathy, pericarditis)
- Nephrotoxin exposure (aminoglycosides, vancomycin, contrast, NSAIDs) is a leading cause of AKI in the ICU; daily medication review and drug level monitoring are essential