Calculating the correct heparin infusion rate is critical in clinical settings to ensure therapeutic anticoagulation while minimizing the risk of hemorrhage. Most heparin protocols require converting a prescribed dose (Units/hr) into a pump flow rate (mL/hr).
The Basic Heparin Formula
To find the infusion rate, you first need to determine the concentration of the heparin bag and then apply the ordered dose.
Step 1: Calculate Concentration
Concentration (Units/mL) = Total Heparin (Units) ÷ Total Volume (mL)
Always double-check heparin calculations with another licensed professional. Heparin is a high-alert medication. Ensure you are using the correct concentration, as heparin is available in various strengths (e.g., 1,000 Units/mL vs 10,000 Units/mL vials).
function calculateHeparinRate() {
var totalUnits = parseFloat(document.getElementById('totalHeparinUnits').value);
var totalVolume = parseFloat(document.getElementById('totalBagVolume').value);
var patientWeight = parseFloat(document.getElementById('patientWeight').value);
var doseValue = parseFloat(document.getElementById('doseInput').value);
var doseUnit = document.getElementById('doseUnit').value;
var resultArea = document.getElementById('heparinResultArea');
var flowRateDisplay = document.getElementById('flowRateResult');
var detailsDisplay = document.getElementById('calcDetails');
if (isNaN(totalUnits) || isNaN(totalVolume) || isNaN(doseValue) || totalUnits <= 0 || totalVolume <= 0 || doseValue <= 0) {
alert("Please enter valid positive numbers for Heparin units, bag volume, and dose.");
return;
}
var hourlyDoseUnits = 0;
// Handle Weight-Based Logic
if (doseUnit === "unitsKgHr") {
if (isNaN(patientWeight) || patientWeight <= 0) {
alert("Please enter a valid patient weight for weight-based dosing.");
return;
}
hourlyDoseUnits = doseValue * patientWeight;
} else {
hourlyDoseUnits = doseValue;
}
// Concentration (Units per mL)
var concentration = totalUnits / totalVolume;
// Final Rate (mL/hr)
var flowRate = hourlyDoseUnits / concentration;
// Round to 1 decimal place
var finalRate = Math.round(flowRate * 10) / 10;
flowRateDisplay.innerText = finalRate;
var detailText = "Concentration: " + concentration.toFixed(2) + " Units/mL. ";
if (doseUnit === "unitsKgHr") {
detailText += "Total hourly dose: " + hourlyDoseUnits.toFixed(0) + " Units/hr.";
}
detailsDisplay.innerText = detailText;
resultArea.style.display = "block";
}