If a patient's fluid gain is 1.3, what should I set the Ultrafiltration (UF) rate to?

Ultrafiltration Rate Setting for 1.3 kg Fluid Gain

Set the ultrafiltration (UF) rate to remove the entire 1.3 kg (1,300 mL) of fluid gain over the duration of the dialysis session, typically resulting in a UF rate of approximately 325-433 mL/hour for a standard 3-4 hour treatment.

Calculation Method

• Calculate total UF volume needed: The patient's fluid gain of 1.3 kg equals 1,300 mL that must be removed 1
• Determine UF rate based on treatment time: Divide total volume by session duration (e.g., 1,300 mL ÷ 4 hours = 325 mL/hour, or 1,300 mL ÷ 3 hours = 433 mL/hour) 1
• Account for weight-based UFR limits: The ultrafiltration rate should ideally remain below 13 mL/kg/hour to minimize adverse outcomes 2

Critical UFR Thresholds and Outcomes

Higher ultrafiltration rates are associated with significantly worse outcomes, particularly in patients on reduced-frequency hemodialysis 2:

• UFR < 6 mL/kg/hour: Reference baseline risk
• UFR 6-10 mL/kg/hour: 43% increased all-cause mortality (HR 1.43) and 73% increased risk of rapid RKF decline 2
• UFR 10-13 mL/kg/hour: 51% increased all-cause mortality (HR 1.51) and 89% increased risk of rapid RKF decline 2
• UFR ≥ 13 mL/kg/hour: 76% increased all-cause mortality (HR 1.76) and 175% increased risk of rapid RKF decline 2

Adjustments for Residual Kidney Function

• If residual urea clearance ≥ 2 mL/min: Measure RKF regularly and consider reducing dialysis frequency or UF requirements, as patients with preserved RKF may tolerate twice-weekly dialysis if fluid gains are not excessive 1
• If residual urea clearance ≥ 5 mL/min/1.73m²: The association between higher UFR and mortality is attenuated, allowing for slightly more aggressive fluid removal if clinically necessary 2
• If residual urea clearance < 2 mL/min: RKF can be ignored in calculations, and standard thrice-weekly dialysis with appropriate UF targets should be maintained 1

Monitoring During Ultrafiltration

• Volumetric measurement: Use volumetric monitoring systems that measure dialysate flow entering and leaving the dialyzer, which provides 99.4% accuracy compared to actual ultrafiltration 3
• Hemodynamic stability: Monitor blood pressure, heart rate, and symptoms of intradialytic hypotension throughout the session 4, 5
• Noninvasive volume monitoring: Consider using in-line hematocrit sensors to track blood volume changes and adjust UFR to minimize intradialytic symptoms 1

Common Pitfalls to Avoid

• Never set UFR without considering patient weight: A 1.3 kg gain may represent a safe UFR for a 100 kg patient (13 mL/kg/hour over 1 hour) but an excessive rate for a 50 kg patient (26 mL/kg/hour) 2
• Never ignore residual kidney function: Patients with significant RKF (≥2 mL/min) may not require full UF of interdialytic weight gain, as native kidneys contribute to fluid removal 1
• Never use excessive UFR to compensate for inadequate dialysis frequency: Patients with frequent fluid gains exceeding safe UFR limits should be transitioned to more frequent dialysis rather than tolerating dangerously high UFR 1, 2
• Never assume weight gain equals pure fluid: In malnourished patients, weight changes may reflect nutritional status rather than fluid overload, and aggressive UF may be harmful 1

Special Considerations for Reduced-Frequency Dialysis

• Twice-weekly dialysis patients: Only appropriate for those with RKF > 2 mL/min, stable renal function, and no excessive fluid gains 1
• If UFR consistently exceeds 10 mL/kg/hour: Strongly consider increasing dialysis frequency to three times weekly to reduce per-session fluid removal and associated mortality risk 2