Critical Care · Year 4 · from Critical Care
Case 3: Rhabdomyolysis-Induced AKI
Clinical Image
Source: Wikimedia Commons - Kidney - CC BY-SA 3.0
Case Presentation
A 32-year-old man is found unresponsive in his apartment after a suspected drug overdose. He was likely down for over 24 hours based on his last contact with family. On arrival, vital signs show heart rate 115 bpm, blood pressure 92/58 mmHg, respiratory rate 22/min, and temperature 38.1C. He is obtunded with GCS 8 and is intubated for airway protection. Physical examination reveals firm, swollen thighs and buttocks from prolonged immobilization on hard surfaces. Initial labs show: potassium 7.2 mEq/L, creatinine 4.8 mg/dL (baseline unknown, likely normal given age), CK greater than 40,000 U/L (markedly elevated), myoglobin 28,000 ng/mL, urine dipstick positive for blood but microscopy shows no RBCs (indicating myoglobinuria). ECG shows peaked T waves and QRS widening. He is diagnosed with rhabdomyolysis-induced AKI with severe hyperkalemia. Emergency treatment for hyperkalemia is initiated (calcium gluconate, insulin/glucose, albuterol). Aggressive IV fluid resuscitation with normal saline is started at 400 mL/hour targeting urine output of 200-300 mL/hour to dilute myoglobin and prevent tubular precipitation. A Foley catheter is placed for precise urine output monitoring. Despite initial fluid resuscitation, he remains oliguric at 20 mL/hour after 4 liters of fluid, and his potassium remains 6.4 mEq/L. Given refractory hyperkalemia with ECG changes and oliguric AKI unresponsive to fluids, emergent hemodialysis is initiated. He requires dialysis for 4 sessions over 8 days, after which his kidney function recovers (creatinine 1.4 mg/dL at discharge). CK trends down appropriately with aggressive hydration.
Key Learning Points
- Rhabdomyolysis causes AKI through myoglobin-induced tubular toxicity, renal vasoconstriction, and tubular obstruction; CK greater than 5,000-10,000 U/L carries significant AKI risk
- Myoglobinuria causes positive urine dipstick for blood without RBCs on microscopy (dipstick detects heme in both hemoglobin and myoglobin)
- Treatment of rhabdomyolysis focuses on aggressive IV crystalloid resuscitation targeting urine output 200-300 mL/hour to dilute myoglobin; bicarbonate for urine alkalinization is controversial
- Indications for RRT in rhabdomyolysis are the same as other AKI: refractory hyperkalemia, acidosis, volume overload, or uremic symptoms