- Enter the patient's weight (kg) — this is the denominator for dose and is required.
- Enter the prescribed circuit flows in mL/hr: dialysate (Qd) for CVVHD/CVVHDF, pre-filter and/or post-filter replacement fluid for CVVH/CVVHDF, and the net ultrafiltration (patient fluid removal). Leave any unused mode blank or 0.
- The total effluent rate, prescribed dose (mL/kg/hr) and ±2 benchmark update automatically against the KDIGO target.
- Optionally enter the hours actually delivered in the last 24 h to convert the prescribed dose into a realistic delivered dose after filter clotting and downtime.
- Optionally enter the blood flow Qb (mL/min) with a pre-filter rate to apply the pre-dilution correction for the clearance lost to dilution of blood before the filter.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this calculator whenever you prescribe, audit, or hand off a CRRT prescription in a critically ill patient with AKI. CRRT dose is defined as the effluent flow rate normalized to body weight (mL/kg/hr), so it must be recalculated whenever a flow setting or the patient's weight changes. It is equally useful at the bedside to confirm that what is actually being delivered — after circuit downtime, clotting, and procedures — still meets the intended target.
Appropriate population
Critically ill adults on continuous modalities — CVVH, CVVHD, or CVVHDF — for AKI or fluid/solute management. Use it when setting initial flows, when titrating the prescription, and during daily review to compare prescribed versus delivered dose and to decide whether to up-prescribe to offset anticipated downtime.
When NOT to rely on it
Effluent-based dose is a clearance surrogate for small solutes; it does not capture middle-molecule clearance, drug removal, or filter efficiency as it ages. The pre-dilution correction here is a first-order approximation (dilution of blood-water before the filter) and does not replace device-specific clearance data. Sustained low-efficiency dialysis (SLED) and intermittent hemodialysis are dosed differently. Always integrate with the clinical picture, fluid balance goals, electrolytes, and your unit's protocol.
Pearls & Pitfalls
Prescribe higher than the target you want delivered
The KDIGO target of 20–25 mL/kg/hr is the delivered dose, not the prescribed one. Because of filter clotting, clamping for imaging and procedures, alarms, and access problems, real-world delivery typically runs 10–20% below the prescription. Most units therefore prescribe ~25–30 mL/kg/hr so that, after downtime, the delivered dose still lands in the target band.
More is not better
The large RENAL (2009) and ATN (2008) trials found no survival or renal-recovery benefit from intensive dosing (~35–40 mL/kg/hr) versus standard dosing (~20–25). Higher intensity increases hypophosphatemia, hypokalemia, drug and micronutrient clearance, and cost without improving outcomes. Aim for the target, not above it.
Pitfalls
(1) Pre-dilution lowers effective clearance — replacement fluid given before the filter dilutes the blood-water entering it, so the effective dose is less than the nominal effluent dose; favor post-dilution or up-prescribe when running heavy pre-dilution. (2) Don't forget to include net ultrafiltration in the effluent total — patient fluid removal contributes to convective clearance. (3) Re-weight matters: dosing to a markedly fluid-overloaded weight under-doses the patient; many units use pre-morbid or ideal weight. (4) A high prescribed dose on paper is meaningless if downtime is high — always reconcile with delivered hours.
Why Use It
Adequate CRRT dosing is one of the few CRRT variables with strong evidence behind it: under-dosing is associated with worse solute control, while routinely exceeding the target wastes resources, clears drugs and electrolytes faster, and confers no survival benefit. Quantifying the dose turns a set of pump rates into a clinically meaningful number that can be compared against a guideline target, audited at the bedside, and handed off precisely between shifts. Crucially, separating the prescribed from the delivered dose exposes the gap created by circuit downtime — the single most common reason patients fall below target — and prompts the practical response of prescribing higher to compensate. It is a foundational calculation in critical-care nephrology and the basis for every CRRT quality metric.
CRRT Dose — Effluent Flow & Delivered Dose
Enter the patient weight and the prescribed circuit flows (mL/hr). The total effluent rate and prescribed dose (mL/kg/hr) update automatically against the KDIGO target. Add delivered hours for a realistic delivered dose, and blood flow Qb with a pre-filter rate for the pre-dilution correction.
⚕ KDIGO AKI Guideline (2012) recommends a delivered effluent dose of 20–25 mL/kg/hr for CRRT; prescribe ~25–30 to offset downtime. RENAL (2009) and ATN (2008) showed no benefit of higher intensity (~35–40) over standard dosing. Effluent dose is a small-solute clearance surrogate and the pre-dilution correction is an approximation. For licensed clinicians; not a substitute for individualized assessment or your unit protocol.
Next Steps
Use the delivered dose against the KDIGO target to titrate the prescription.
- Delivered < 20 mL/kg/hr: under-dosing. Increase the prescription, address the cause of downtime (anticoagulation/filter life, access, procedures), and recheck delivered hours over the next 24 h.
- Delivered 20–25 mL/kg/hr: on target. Continue and re-audit daily, and re-normalize to weight if the patient's weight changes substantially.
- Delivered 25–35 mL/kg/hr: acceptable but watch — there is no outcome benefit above target, so monitor phosphate, potassium, and drug/antimicrobial dosing, and consider trimming flows.
- If running heavy pre-dilution, account for the reduced effective clearance (shown when Qb is entered) — favor post-dilution or up-prescribe.
- Pair with the dialysis prescription tool and the net ultrafiltration rate calculator for fluid-removal targets.
Evidence & References
Formula
| Quantity | Formula |
|---|---|
| Total effluent (mL/hr) | Qd + pre-replacement + post-replacement + net UF |
| Prescribed dose (mL/kg/hr) | Total effluent ÷ weight (kg) |
| Delivered dose (mL/kg/hr) | Prescribed dose × (delivered hours ÷ 24) |
| Pre-dilution factor | Qb ÷ (Qb + pre-replacement converted to mL/min) |
| Effective dose (mL/kg/hr) | Dose × pre-dilution factor |
Interpretation (delivered dose)
| Delivered effluent dose | Interpretation |
|---|---|
| < 20 mL/kg/hr | Under-dosing — increase prescription / reduce downtime |
| 20–25 mL/kg/hr | On target (KDIGO recommended delivered dose) |
| 25–35 mL/kg/hr | Acceptable but watch — no outcome benefit above target |
| > 35 mL/kg/hr | Excess intensity — no benefit; greater electrolyte/drug clearance |
KDIGO recommends a delivered dose of 20–25 mL/kg/hr; because delivery falls short of prescription owing to downtime and clotting, prescribe ~25–30 mL/kg/hr. The RENAL and ATN randomized trials established that higher-intensity CRRT (~35–40 mL/kg/hr) confers no mortality or renal-recovery benefit over standard dosing, while the earlier Ronco trial supported a minimum effective dose. Pre-dilution dilutes blood-water before the filter and lowers effective small-solute clearance.
References
- Kidney Disease: Improving Global Outcomes (KDIGO) AKI Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl. 2012;2(1):1–138.
- RENAL Replacement Therapy Study Investigators; Bellomo R, et al. Intensity of continuous renal-replacement therapy in critically ill patients. N Engl J Med. 2009;361(17):1627–1638.
- VA/NIH Acute Renal Failure Trial Network; Palevsky PM, et al. Intensity of renal support in critically ill patients with acute kidney injury. N Engl J Med. 2008;359(1):7–20.
- Ronco C, et al. Effects of different doses in continuous veno-venous haemofiltration on outcomes of acute renal failure. Lancet. 2000;356(9223):26–30.
