function calculateUFR() {
// Get input values
var preWeight = parseFloat(document.getElementById('preWeight').value);
var targetWeight = parseFloat(document.getElementById('targetWeight').value);
var time = parseFloat(document.getElementById('treatmentTime').value);
var intake = parseFloat(document.getElementById('fluidIntake').value);
// Validation
if (isNaN(preWeight) || isNaN(targetWeight) || isNaN(time)) {
alert("Please enter valid numbers for Weight and Time.");
return;
}
if (time <= 0) {
alert("Treatment duration must be greater than 0.");
return;
}
if (isNaN(intake)) {
intake = 0;
}
// Logic
// 1. Calculate weight difference (kg)
var weightDiff = preWeight – targetWeight;
// 2. Convert kg to mL (1 kg = 1000 mL)
var fluidFromWeight = weightDiff * 1000;
// 3. Add intradialytic intake (rinseback, drinks, etc.)
var totalVolume = fluidFromWeight + intake;
// Check for negative removal
if (totalVolume < 0) {
alert("Target weight is higher than current weight + intake. No fluid removal needed.");
document.getElementById('ufrResults').style.display = 'none';
return;
}
// 4. Calculate Hourly UFR (mL/hr)
var hourlyRate = totalVolume / time;
// 5. Calculate Adjusted UFR (mL/kg/hr) based on Dry Weight (Target Weight)
// Note: Clinical guidelines typically use Dry Weight for this normalization
var adjustedRate = hourlyRate / targetWeight;
// Display Results
document.getElementById('weightDiff').innerText = weightDiff.toFixed(2) + " kg";
document.getElementById('totalVolume').innerText = Math.round(totalVolume) + " mL";
document.getElementById('hourlyUFR').innerText = Math.round(hourlyRate) + " mL/hr";
document.getElementById('adjustedUFR').innerText = adjustedRate.toFixed(1);
// Risk Assessment
var riskDiv = document.getElementById('riskIndicator');
var badgeHTML = "";
if (adjustedRate <= 10) {
badgeHTML = 'Safe Range (< 10)';
} else if (adjustedRate > 10 && adjustedRate <= 13) {
badgeHTML = 'Caution (10-13)';
} else {
badgeHTML = 'High Risk (> 13)';
}
riskDiv.innerHTML = badgeHTML;
document.getElementById('ufrResults').style.display = 'block';
}
How to Calculate Ultrafiltration Rate in Dialysis
The Ultrafiltration Rate (UFR) is a critical metric in hemodialysis prescription. It represents the speed at which fluid is removed from a patient's blood during a dialysis session. Calculating the correct UFR is essential for preventing complications such as intradialytic hypotension (low blood pressure), cramping, and myocardial stunning (stress on the heart).
Clinical Guideline: Recent studies suggest that an Ultrafiltration Rate greater than 13 mL/kg/hr is associated with increased mortality and cardiovascular events. Many clinics aim for a rate below 10 mL/kg/hr for maximum safety.
The Ultrafiltration Formula
To calculate the UFR manually, you need to account for the patient's weight gain and any additional fluids administered during the treatment (such as the saline rinseback, IV medications, or oral intake).
Step 1: Determine Total Fluid to Remove
First, calculate the difference between the patient's pre-dialysis weight and their prescribed target (dry) weight. Remember that 1 kg of weight is roughly equivalent to 1000 mL (1 Liter) of fluid.
In this example, the rate of 7.5 mL/kg/hr is well within the safe zone (under 10 mL/kg/hr).
Why is UFR Important?
Removing fluid too quickly allows less time for the plasma to refill from the surrounding tissues. This causes a drop in blood volume, leading to low blood pressure. High UFRs have been linked to:
Myocardial Stunning: Temporary loss of heart function due to reduced blood flow.
Increased Mortality: Higher risks of cardiovascular death over time.
Patient Discomfort: Severe leg cramps, nausea, and dizziness during treatment.
If the calculated UFR exceeds 13 mL/kg/hr, clinicians often recommend extending the treatment time or adjusting the frequency of dialysis sessions to remove fluid more gently.