Natriuretic Response Prediction Equation (NRPE)

NRPE Calculator

Natriuretic Response Prediction Equation (NRPE) calculator for predicting natriuretic response to intravenous loop diuretics. Enter values from a spot urine sample obtained about 2 hours after the IV loop diuretic dose.

eGFR (mL/min/1.73 m²)

Estimated glomerular filtration rate.

Height (cm)

Used to calculate body surface area by the Mosteller formula.

Weight (kg)

Used to calculate body surface area.

Serum creatinine (mg/dL)

Must use the same creatinine units as urine creatinine.

Spot urine creatinine (mg/dL)

Use matching units with serum creatinine.

Spot urine sodium (mmol/L)

Spot urine sodium from the ~2-hour sample.

Predicted 6-hour sodium output: 0 mmol

Predicted 6-hour urine output: 0.00 L

Calculated BSA: 0.00 m²

Estimated urine flow rate: 0.0 mL/hour

Interpretation: —

NRPE response bands: poor <50 mmol, suboptimal 50 to <100 mmol, adequate 100 to 150 mmol, excellent >150 mmol.

This calculator supports early assessment of diuretic response in acute heart failure settings. It does not replace clinical judgment, hemodynamic assessment, or a full treatment protocol.

Formula used:
Predicted 6-hour sodium output = eGFR × (BSA/1.73) × (Serum Cr/Urine Cr) × 60 × 3.25 × (Urine Na/1000)
Predicted 6-hour urine output = eGFR × (BSA/1.73) × (Serum Cr/Urine Cr) × 60 × 3.25 / 1000
BSA calculated by Mosteller: sqrt((height(cm) × weight(kg))/3600)

The published NRPE estimates 6-hour urinary sodium output using a spot urine sample collected about 2 hours after IV loop diuretic administration. The equation commonly presented is:

Predicted 6-hour sodium output (mmol) = eGFR × (BSA / 1.73) × (Serum Cr / Urine Cr) × 60 × 3.25 × (Urine Na / 1000)

This works by first estimating the instantaneous urine flow rate from kidney function and the serum-to-urine creatinine ratio, then multiplying by urine sodium concentration. That same flow estimate can also be used to estimate predicted 6-hour urine output in liters.

Published response thresholds often used with NRPE are:

<50 mmol: poor natriuretic response
50 to <100 mmol: suboptimal response
100 to 150 mmol: adequate/good response
>150 mmol: excellent response

NRPE Calculator

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