Please enter a valid weight and at least one flow rate.
Total Effluent Flow Rate (Qeff):0 mL/hr
Calculated Effluent Dose:0 mL/kg/hr
24-Hour Total Volume:0 L
Target Assessment:
function calculateCRRT() {
var weightInput = document.getElementById('patientWeight');
var dialysateInput = document.getElementById('dialysateFlow');
var replacementInput = document.getElementById('replacementFlow');
var removalInput = document.getElementById('fluidRemoval');
var errorDiv = document.getElementById('errorDisplay');
var resultsDiv = document.getElementById('results');
// Parse inputs
var weight = parseFloat(weightInput.value);
var qd = parseFloat(dialysateInput.value) || 0;
var qrf = parseFloat(replacementInput.value) || 0;
var qnet = parseFloat(removalInput.value) || 0;
// Validation
if (isNaN(weight) || weight <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerText = "Please enter a valid patient weight greater than 0.";
resultsDiv.style.display = 'none';
return;
}
if (qd === 0 && qrf === 0 && qnet === 0) {
errorDiv.style.display = 'block';
errorDiv.innerText = "Please enter at least one flow rate value (Dialysate, Replacement, or Removal).";
resultsDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// Calculation Logic
// Total Effluent Flow Rate (Qeff) = Qd + Qrf + Qnet
var totalEffluent = qd + qrf + qnet;
// Effluent Dose = Qeff / Weight
var effluentDose = totalEffluent / weight;
// 24 Hour Volume in Liters
var dailyVolumeLiters = (totalEffluent * 24) / 1000;
// Display Results
document.getElementById('totalEffluentDisplay').innerText = Math.round(totalEffluent) + " mL/hr";
document.getElementById('doseDisplay').innerText = effluentDose.toFixed(1) + " mL/kg/hr";
document.getElementById('dailyVolumeDisplay').innerText = dailyVolumeLiters.toFixed(1) + " L";
// Target Assessment (Based on KDIGO guidelines of 20-25 mL/kg/hr)
var assessmentSpan = document.getElementById('targetAssessment');
if (effluentDose < 20) {
assessmentSpan.innerText = "Below Standard Target (= 20 && effluentDose 30 mL/kg/hr)";
assessmentSpan.style.color = "#fd7e14"; // Orange
}
resultsDiv.style.display = 'block';
}
Understanding CRRT Effluent Rate Calculation
Continuous Renal Replacement Therapy (CRRT) is a critical intervention for hemodynamically unstable patients with Acute Kidney Injury (AKI). Precise calculation of the effluent rate is essential to ensure the patient receives the prescribed dose of therapy. The effluent rate represents the total volume of fluid leaving the hemofilter per hour, which correlates directly with the clearance of solutes.
In clinical settings, the "dose" of CRRT is typically expressed in milliliters per kilogram of body weight per hour (mL/kg/hr). Current KDIGO guidelines generally recommend a delivered effluent dose of 20–25 mL/kg/hr.
The Effluent Rate Formula
To calculate the total effluent flow rate ($Q_{eff}$), you must sum all fluids that exit the filter as waste. This includes the spent dialysate, the replacement fluid (which becomes ultrafiltrate), and the net fluid removed from the patient for volume control.
$$Q_{eff} = Q_d + Q_{rf} + Q_{net}$$
Where:
$Q_{eff}$: Total Effluent Flow Rate (mL/hr)
$Q_d$: Dialysate Flow Rate (mL/hr) – Used in CVVHD and CVVHDF modes.
$Q_{rf}$: Replacement Fluid Flow Rate (mL/hr) – The sum of pre-blood pump and post-blood pump replacement fluids used in CVVH and CVVHDF modes.
$Q_{net}$: Net Ultrafiltration Rate (mL/hr) – The rate of fluid removal programmed to achieve negative fluid balance (patient weight loss).
Calculating the Prescribed Dose
Once the Total Effluent Flow Rate is determined, the actual therapeutic dose delivered to the patient is calculated by normalizing this flow rate against the patient's weight.
This dose falls within the optimal range, ensuring adequate solute clearance while minimizing the risk of hypophosphatemia or other complications associated with very high-volume hemofiltration.
Why Use an Effluent Rate Calculator?
Manual calculations in the ICU can be prone to error due to the complexity of varying modalities (CVVH, CVVHD, CVVHDF). Using a CRRT effluent rate calculator ensures:
Accuracy: Prevents mathematical errors in summing multiple flow rates.
Compliance: Helps clinicians quickly verify if the current settings meet KDIGO or institutional protocols.
Adjustment: Allows for rapid recalculation when patient weight changes or when fluid removal goals are altered.
Note: This tool calculates the effluent volume based dose. Actual delivered dose may be lower due to therapy downtime (changing bags, clotting, alarms). It is often recommended to prescribe a slightly higher dose (e.g., 25-30 mL/kg/hr) to ensure a delivered dose of at least 20 mL/kg/hr.