- Enter the patient's post-dialysis (target / dry) weight in kg and the treatment time in hours — UFR is normalized to post-dialysis weight.
- Optionally enter the planned UF volume (total fluid to remove this session) to get this session's UFR and risk band.
- Flag whether the patient is cardiovascularly vulnerable (heart failure, LV dysfunction, CAD, elderly, diabetes, or autonomic dysfunction) — this tightens the recommended target.
- Read the UFR (mL/kg/h), its risk category, and the maximum safe UF volume at the ≤10 target and ≤13 ceiling.
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When to Use
Use when planning or auditing a maintenance hemodialysis prescription to keep fluid removal within a cardiovascularly safe rate — setting a per-session UF ceiling, deciding whether to extend treatment time or add sessions, and for unit quality benchmarks.
Appropriate use
Maintenance HD patients with a known post-dialysis target weight and session length. Pair with assessment of intradialytic hypotension, residual kidney function, and interdialytic weight gain.
Caveats
UFR is one of several determinants of intradialytic tolerability — it does not replace assessment of volume status, blood-pressure trends, or symptoms. The thresholds come from observational data, not randomized trials.
Pearls & Pitfalls
Lower is better — aim ≤10
Risk rises continuously, beginning below the classic 13 mL/kg/h cutoff. Target the lowest practical UFR (often ≤10), keeping 13 mL/kg/h as an absolute ceiling rather than a pass/fail line.
How to reduce UFR
Extend treatment time, add sessions, and restrict interdialytic sodium/fluid to limit weight gain — longer/slower sessions remove the same volume at a lower rate. Reassess the dry weight.
Pitfalls
Normalize to post-dialysis (not pre-dialysis) weight. High UFR is especially harmful in heart failure, CAD, the elderly, and diabetics with autonomic dysfunction — keep these patients well under the ceiling. A "passing" UFR does not guarantee hemodynamic stability.
Why Use It
Rapid fluid removal causes myocardial stunning, recurrent ischemia, and hemodynamic instability. Large observational cohorts show stepwise increases in cardiovascular and all-cause mortality as UFR rises above ~10–13 mL/kg/h, making UFR a modifiable lever for reducing dialysis-associated cardiovascular harm.
Ultrafiltration Rate & Maximum Safe UF Volume
Enter post-dialysis weight and treatment time (and optionally the planned UF volume) to compute the UFR, its risk band, and the maximum UF volume at the ≤10 mL/kg/h target and ≤13 mL/kg/h ceiling.
⚕ UFR (mL/kg/h) = UF volume (mL) ÷ [post-dialysis weight (kg) × treatment time (h)]. Risk bands: <8 excellent · 8–10 acceptable · 10–13 caution · >13 high risk (Flythe 2011; Assimon 2016). Thresholds are observational, not from randomized trials, and supplement — not replace — clinical judgment.
Next Steps
If the UFR is in the caution / high-risk band:
- Extend treatment time or add a session to spread the same UF volume over more hours.
- Reassess the dry weight; reduce interdialytic weight gain through sodium/fluid restriction and counseling.
- For cardiovascularly vulnerable patients, target ≤10 mL/kg/h (lower if tolerated) and watch for intradialytic hypotension and cramping.
- Document the per-session UF ceiling in the prescription and re-audit periodically.
Evidence & References
Formula
| Quantity | Equation |
|---|---|
| Ultrafiltration rate | UFR (mL/kg/h) = UF volume (mL) ÷ [post-dialysis weight (kg) × time (h)] |
| Max UF volume at a target rate | UFmax (L) = target UFR (mL/kg/h) × weight (kg) × time (h) ÷ 1000 |
Risk bands
| UFR (mL/kg/h) | Interpretation |
|---|---|
| < 8 | Excellent |
| 8–10 | Acceptable |
| 10–13 | Caution zone — risk rises before 13 |
| > 13 | High risk; avoid when possible |
Evidence & References
The thresholds derive from large observational cohorts, not randomized trials. Flythe et al. (2011) found a UFR >13 mL/kg/h associated with higher cardiovascular and all-cause mortality, establishing the 13 mL/kg/h benchmark; Assimon et al. (2016, >118,000 patients) showed ~31% higher mortality at >13 and ~22% higher at >10 mL/kg/h versus lower rates — supporting a ≤10 mL/kg/h target with ≤13 as the absolute ceiling.
- Flythe JE, Kimmel SE, Brunelli SM. Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality. Kidney Int. 2011;79(2):250-257.
- Assimon MM, Wenger JB, Wang L, Flythe JE. Ultrafiltration rate and mortality in maintenance hemodialysis patients. Am J Kidney Dis. 2016;68(6):911-922.
- Flythe JE, et al. Ultrafiltration rate clinical performance measures and dialysis outcomes — supporting cohort analyses.
- National Kidney Foundation. KDOQI Clinical Practice Guideline for Hemodialysis Adequacy: 2015 Update. Am J Kidney Dis. 2015;66(5):884-930.
