Critical Care · Year 4 · from Critical Care
Case 2: Contrast-Induced AKI and CRRT Management
Clinical Image
Source: Wikimedia Commons - Hemodialysis - CC BY-SA 4.0
Case Presentation
A 70-year-old woman with chronic kidney disease stage 3b (baseline creatinine 2.4 mg/dL, eGFR 38) and coronary artery disease undergoes cardiac catheterization for unstable angina. Despite pre-procedure hydration with normal saline and use of low-osmolar contrast (150 mL total), her creatinine rises from 2.4 to 4.1 mg/dL on post-procedure day 2. Urine output decreases to 300 mL over 24 hours. Renal ultrasound shows no hydronephrosis. She is diagnosed with contrast-induced AKI (Stage 2 KDIGO). Her medications are reviewed: lisinopril and metformin are held. Nephrotoxins are avoided. Despite conservative management, by day 4 her creatinine peaks at 5.8 mg/dL, she develops pulmonary edema refractory to IV furosemide (no response to 160 mg IV), and her potassium rises to 5.6 mEq/L. Given volume overload unresponsive to diuretics and progressive AKI with oliguria, CRRT is initiated. A 13.5 French dialysis catheter is placed in the right femoral vein (internal jugular avoided due to her severe pulmonary edema requiring upright positioning). CVVHDF is started with citrate anticoagulation, effluent rate of 25 mL/kg/hour, and initial fluid removal goal of 100 mL/hour. Labs are monitored every 6 hours including ionized calcium (for citrate anticoagulation management). Over 48 hours, 4 liters of net fluid are removed, her respiratory status improves, and she no longer requires supplemental oxygen. After 5 days of CRRT, her urine output improves to 50 mL/hour, and CRRT is discontinued. She is discharged 10 days after catheterization with creatinine 3.2 mg/dL and follow-up with nephrology scheduled.
Key Learning Points
- Contrast-induced AKI typically occurs 24-72 hours post-exposure; risk factors include pre-existing CKD, diabetes, volume depletion, high contrast volumes, and concurrent nephrotoxins
- Prevention strategies include pre-procedure hydration (isotonic saline), using minimal contrast volume, and avoiding concurrent nephrotoxins; evidence for N-acetylcysteine is limited
- CRRT is preferred over intermittent hemodialysis in hemodynamically unstable patients as it provides slower, more physiologic fluid and solute removal
- CRRT dosing targets effluent rate of 20-25 mL/kg/hour; regional citrate anticoagulation is preferred as it reduces bleeding risk while maintaining circuit patency