1. What is Filtration Fraction in CRRT?

Definition: Filtration Fraction (FF) represents the proportion of plasma water that is filtered during Continuous Renal Replacement Therapy (CRRT).

Purpose: It helps clinicians assess the efficiency of the CRRT process and prevent hemoconcentration which can lead to filter clotting.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( FF \) — Filtration Fraction (dimensionless)
• \( GFR \) — Glomerular Filtration Rate (mL/min)
• \( Q_p \) — Plasma Flow Rate (mL/h)

Explanation: The GFR is divided by the plasma flow rate (converted to mL/min by dividing by 60) to determine what fraction of plasma water is being filtered.

3. Importance of Filtration Fraction

Details: Maintaining an appropriate FF (typically < 20-25%) is crucial to prevent hemoconcentration, filter clotting, and ensure effective therapy.

4. Using the Calculator

Tips: Enter the GFR in mL/min and plasma flow rate (Q_p) in mL/h. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal FF range in CRRT?
A: Typically 15-25%. Values >25-30% increase risk of filter clotting due to hemoconcentration.

Q2: How do I measure Q_p in clinical practice?
A: Q_p can be estimated from blood flow rate and hematocrit: Q_p = Q_b × (1 - Hct).

Q3: Why is the 60 in the denominator?
A: It converts Q_p from mL/h to mL/min to match GFR units (mL/min).

Q4: What affects filtration fraction?
A: Blood flow rate, hematocrit, ultrafiltration rate, and membrane characteristics.

Q5: How can I reduce FF if it's too high?
A: Increase blood flow rate, decrease ultrafiltration rate, or use predilution.