Ultrafiltration in Cardiac Patients with CKD
Ultrafiltration may be considered for cardiac patients with CKD who have obvious volume overload or refractory congestion not responding to diuretic therapy, though it should be reserved for selected cases rather than used as first-line treatment. 1
Clinical Context and Indications
Ultrafiltration (including isolated ultrafiltration and slow continuous ultrafiltration/SCUF) is classified as a Class IIb recommendation (may be considered) by ACC/AHA guidelines for specific scenarios: 1
- Patients with obvious volume overload to alleviate congestive symptoms and reduce fluid weight 1
- Patients with refractory congestion not responding to medical therapy 1
- Diuretic-resistant patients with cardiac failure and fluid overload where dialysis is not required 2
The European Society of Cardiology similarly recommends considering venovenous isolated ultrafiltration when patients remain in pulmonary edema despite doubled diuretic doses and adequate left ventricular filling pressure. 1
Mechanism and Advantages
Ultrafiltration moves water and small- to medium-weight solutes across a semipermeable membrane to reduce volume overload. 1 Because the electrolyte concentration removed is similar to plasma, relatively more sodium can be removed compared to diuretics alone. 1 This technique has been shown to reduce neurohormone levels and increase diuretic responsiveness in heart failure patients. 1
In the cardiorenal syndrome population specifically, continuous veno-venous hemofiltration or SCUF may increase renal blood flow, improve renal function, and restore diuretic efficiency. 3
Evidence Quality and Limitations
A critical caveat: A randomized trial in patients with cardiorenal syndrome and persistent congestion failed to demonstrate significant advantage of ultrafiltration over bolus diuretic therapy. 1 While an earlier trial of 200 unselected acute heart failure patients showed ultrafiltration reduced weight at 48 hours and improved 90-day readmission rates compared to diuretics, 1 the evidence remains mixed.
The hemodynamic stability advantage is notable—SCUF maintains stable blood pressure and pulse rate during significant fluid removal (averaging 2,189 mL per session), unlike aggressive diuresis which can cause hypotension. 2
Practical Implementation Considerations
Consultation with a nephrologist is appropriate before initiating ultrafiltration, especially when the non-nephrology provider lacks sufficient experience. 1 Key concerns include: 1
- Cost considerations
- Need for veno-venous access
- Provider experience requirements
- Nursing support availability
For patients with severe renal dysfunction and refractory fluid retention, continuous techniques like SCUF may be necessary to achieve adequate control when diuretics fail. 3
Treatment Algorithm Position
Ultrafiltration should be positioned in the treatment hierarchy as follows:
- First-line: Aggressive intravenous loop diuretics (at doses equal to or exceeding chronic oral daily dose) 1
- Second-line: Intensify diuretic regimen with combination therapy (add thiazide or metolazone) 4, 5
- Third-line: Consider low-dose dopamine infusion (2.5 μg/kg/min) to enhance diuresis 1
- Fourth-line: Ultrafiltration for persistent volume overload despite above measures 1
Monitoring During Ultrafiltration
Hemodynamic instability due to overaggressive fluid removal must be avoided. 6 Monitor: 6
- Clinical signs of volume status
- Biomarker values
- Blood pressure and heart rate continuously
- Renal function (creatinine typically remains stable during appropriate ultrafiltration) 7
Special Population Outcomes
In cardiac patients with volume overload treated with ultrafiltration, in-hospital mortality for heart failure patients was 7.6%, comparable to expected mortality. 7 Importantly, no deaths were directly related to ultrafiltration use in this series. 7 Long-term survival was 71% at 1 year and 67% at 2 years, with decreased systolic blood pressure (not ultrafiltration volume) predicting mortality. 7