Indications for CRRT in CVICU Patients with Acute Kidney Injury
Continuous Renal Replacement Therapy (CRRT) is strongly recommended for hemodynamically unstable patients with AKI in the CVICU setting, as it provides superior hemodynamic tolerance compared to intermittent modalities. 1
Primary Indications for CRRT in CVICU
- Hemodynamic instability: CRRT is the preferred modality for patients requiring vasopressor support or with cardiovascular instability, as it allows for more gradual fluid and solute removal 1
- Acute brain injury or increased intracranial pressure: CRRT is recommended over intermittent hemodialysis due to lower risk of cerebral edema and intracranial pressure fluctuations 1
- Fluid overload management: CRRT provides better control of fluid balance in critically ill cardiac patients, especially when positive fluid balance cannot be managed by intermittent hemodialysis 1
- Metabolic derangements: CRRT should be initiated when metabolic and fluid demands exceed the kidney's capacity, particularly for management of severe acid-base and electrolyte disturbances 1, 2
Specific CVICU Considerations
- ECMO patients: CRRT is particularly important in ECMO patients for preventing and managing fluid overload, which is critical for optimal ECMO function 3
- Multi-organ support: For patients requiring extracorporeal life support (ECLS) such as ECMO or ventricular assist devices, CRRT should be integrated based on institutional expertise and available technology 1, 3
- Post-cardiac surgery: CRRT should be considered early in post-cardiac surgery patients with AKI who demonstrate fluid overload resistant to diuretic therapy 4
Technical Aspects of CRRT Implementation
Access and Setup
- Use an uncuffed nontunneled dialysis catheter for initiating CRRT 1
- Preferred vascular access sites (in order): right jugular vein, femoral vein, left jugular vein, and subclavian vein as last choice 1, 5
- Always use ultrasound guidance for catheter insertion and obtain chest radiograph before first use of internal jugular or subclavian catheters 1
Anticoagulation Protocol
- For patients without increased bleeding risk, regional citrate anticoagulation is recommended 1, 5
- For patients with heparin-induced thrombocytopenia, use direct thrombin inhibitors (argatroban) or Factor Xa inhibitors 1
- Avoid regional heparinization in patients with increased bleeding risk 1
Dosing and Monitoring
- Deliver an effluent volume of 20-25 mL/kg/h for CRRT in AKI 1, 6
- Use bicarbonate rather than lactate as buffer in dialysate and replacement fluid, especially for patients with circulatory shock, liver failure, or lactic acidemia 1, 5
- Frequently assess the actual delivered dose to adjust prescription as needed 1, 6
When to Transition from CRRT to Intermittent Modalities
- Consider transitioning from CRRT to intermittent hemodialysis when 1:
- Vasopressor support has been discontinued
- Hemodynamic stability has been achieved
- Intracranial hypertension has resolved
- Positive fluid balance can be adequately controlled by intermittent hemodialysis
Pitfalls to Avoid
- Don't rely solely on single BUN and creatinine thresholds for initiating CRRT; consider the broader clinical context 5
- Avoid using subclavian veins for access due to risk of thrombosis and stenosis 5
- Don't use lactate-buffered solutions in patients with liver failure or lactic acidosis 1, 5
- Ensure delivered dose matches prescribed dose by accounting for treatment interruptions and filter clotting 6
- Monitor for negative fluid balance during CRRT, as excessive fluid removal has been associated with worse outcomes in some studies 4