function calculateInfusion() {
// reset displays
document.getElementById('resultDisplay').style.display = 'none';
document.getElementById('errorDisplay').style.display = 'none';
// Get input values
var volume = parseFloat(document.getElementById('totalVolume').value);
var hours = parseFloat(document.getElementById('timeHours').value);
var minutes = parseFloat(document.getElementById('timeMinutes').value);
var dropFactor = parseFloat(document.getElementById('dropFactor').value);
// Handle empty or NaN inputs for time
if (isNaN(hours)) hours = 0;
if (isNaN(minutes)) minutes = 0;
// Validation
if (isNaN(volume) || volume <= 0) {
var err = document.getElementById('errorDisplay');
err.innerHTML = "Please enter a valid positive Total Volume.";
err.style.display = 'block';
return;
}
if ((hours === 0 && minutes === 0) || (hours < 0 || minutes < 0)) {
var err = document.getElementById('errorDisplay');
err.innerHTML = "Please enter a valid time duration (greater than 0).";
err.style.display = 'block';
return;
}
// Calculations
var totalMinutes = (hours * 60) + minutes;
var totalHours = totalMinutes / 60;
// Flow Rate (mL/hr)
// Formula: Volume / Hours
var flowRate = volume / totalHours;
// Drop Rate (gtt/min)
// Formula: (Volume * Drop Factor) / Total Minutes
var dropRate = (volume * dropFactor) / totalMinutes;
// Display Results
// Flow rate usually rounded to 1 decimal place
// Drop rate must be a whole number (you cannot count partial drops physically)
document.getElementById('flowRateResult').innerText = flowRate.toFixed(1);
document.getElementById('dropRateResult').innerText = Math.round(dropRate);
document.getElementById('totalMinutesResult').innerText = totalMinutes;
document.getElementById('resultDisplay').style.display = 'block';
}
How to Calculate the Infusion Rate: A Guide for Nurses
Accurately calculating the infusion rate is a critical skill in nursing and healthcare. Administering Intravenous (IV) fluids or medications requires precise math to ensure patient safety. Whether you are using an electronic infusion pump or a manual gravity drip set, understanding the formulas behind the flow rate is essential.
Understanding the Variables
To perform these calculations, you need three pieces of data:
Total Volume (mL): The amount of fluid to be administered.
Time (Hours/Minutes): How long the fluid must take to infuse completely.
Drop Factor (gtt/mL): The calibration of the IV tubing set. This number indicates how many drops it takes to make 1 milliliter. This is found on the tubing packaging.
Common Drop Factors
IV tubing generally comes in two types:
Macrodrip sets: Deliver large drops. Standard sizes are 10, 15, or 20 gtt/mL. These are used for standard fluid resuscitation or general maintenance fluids.
Microdrip sets: Deliver tiny drops. The standard size is 60 gtt/mL. These are used for precise dosing, pediatrics, or potent medications.
The Formulas
1. Calculating Flow Rate (mL/hr)
This is used when setting an electronic infusion pump. The pump regulates the fluid based on milliliters per hour.
Flow Rate (mL/hr) = Total Volume (mL) ÷ Time (Hours)
2. Calculating Drop Rate (gtt/min)
This is used for manual gravity IV lines. You count the drops falling in the drip chamber for one minute to set the rate.
Drop Rate (gtt/min) = (Total Volume (mL) × Drop Factor (gtt/mL)) ÷ Time (Minutes)
Clinical Examples
Example 1: Electronic Pump
Order: Infuse 1,000 mL of Normal Saline over 8 hours. Calculation: 1,000 mL ÷ 8 hours = 125 mL/hr.
Example 2: Manual Gravity Drip
Order: Infuse 500 mL of Antibiotic Solution over 2 hours (120 minutes) using tubing with a drop factor of 15 gtt/mL. Calculation: (500 mL × 15 gtt/mL) ÷ 120 minutes
= 7,500 ÷ 120
= 62.5 (Round to 63 gtt/min).
Tips for Accurate Calculation
Convert units first: Always ensure your time is converted to minutes if using the drop rate formula.
Rounding: For gtt/min, always round to the nearest whole number because you cannot physically count a fraction of a drop. For pumps (mL/hr), many modern pumps can accept decimals (e.g., 12.5 mL/hr), but always verify your facility's policy.
Verify the Drop Factor: Never assume the drop factor is 10 or 15. Always check the packaging of the tubing you are currently using.