CRRT terms and calculations

• related: CRRT continuous renal replacement therapy
• tags: #literature #nephrology

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Essential Terms

• Kurea: solute removal rate
• solvent drag: when water goes across membrane, it drags solutes with it

• Qrf: replacement fluid, 1.7 L/hg
• UF, ultrafiltration, 75 cc/hr
• Qb, blood flow rate, 200cc/hr

Formulas

$$\text{CVVH Dose} = \frac{\text{Effluent Rate}}{\text{IBW}} = \frac{Q_{rf}+UF}{Kg}$$ $$\text{Plasma Flow} = \text{blood flow} * 60 * (1-Hct)$$ $$\text{Filtration Fraction} = \frac{\text{Effluent rate}}{\text{Replacement Fluid}+\text{Plasma Flow}} = \frac{Q_{rf}+UF}{Q_{rf} + Q_p}$$ $$\text{Dilution Factor} = \frac{Q_p}{Q_p + Q_{rf}}$$

Dose

Blood Flow Rate

• faster flow = faster cartridge use
• faster flow = decreased filtration
• post filter and pre-blood doesn’t need to be accounted

Dilution Factor

• dilution factor is plasma flow or blood flow

Filtration Fraction

• may decrease renal recovery odds with very high UF = low circulating volume

Examples

• Qrf: replacement fluid, target 20-25 cc/kg/hr ¹

Links to this note

• CRRT continuous renal replacement therapy
  • CRRT terms and calculations

Footnotes

1. Bryant CRRT lecture 11 2026 ↩