function calculateIVFlowRate() {
// 1. Get DOM elements
var volumeInput = document.getElementById('iv_volume');
var timeInput = document.getElementById('iv_time');
var unitInput = document.getElementById('iv_time_unit');
var factorInput = document.getElementById('iv_drop_factor');
var resultsArea = document.getElementById('iv_results_area');
var errorMsg = document.getElementById('iv_error_msg');
var mlHrDisplay = document.getElementById('result_ml_hr');
var gttMinDisplay = document.getElementById('result_gtt_min');
var dripContainer = document.getElementById('drip_rate_container');
// 2. Parse values
var volume = parseFloat(volumeInput.value);
var time = parseFloat(timeInput.value);
var unit = unitInput.value;
var dropFactor = parseFloat(factorInput.value);
// 3. Reset display
resultsArea.style.display = 'none';
errorMsg.style.display = 'none';
dripContainer.style.display = 'none';
// 4. Validation
if (isNaN(volume) || volume <= 0) {
errorMsg.innerHTML = "Please enter a valid positive volume in ml.";
errorMsg.style.display = 'block';
return;
}
if (isNaN(time) || time 0) {
// Formula: (Volume (ml) * Drop Factor (gtt/ml)) / Time (min)
// OR: (Flow Rate (ml/hr) * Drop Factor) / 60
var dripRate = (flowRate * dropFactor) / 60;
// Drip rate must be a whole number (you can't count partial drops easily)
dripRateFormatted = Math.round(dripRate);
dripContainer.style.display = 'block';
}
// 7. Update UI
mlHrDisplay.innerHTML = flowRateFormatted + " ml/hr";
if (dripRateFormatted !== null) {
gttMinDisplay.innerHTML = dripRateFormatted + " gtt/min";
}
resultsArea.style.display = 'block';
}
Understanding IV Flow Rate Calculation
Calculating the correct intravenous (IV) flow rate is a fundamental skill in nursing and healthcare. It ensures that patients receive the prescribed volume of medication or fluids over a specific period, preventing complications associated with under-infusion (dehydration, lack of therapeutic effect) or over-infusion (fluid overload, toxicity).
The Basic Formula for ml/hr
When setting up an electronic infusion pump, the primary metric required is milliliters per hour (ml/hr). This determines the speed at which the machine pushes fluid into the vein.
Flow Rate (ml/hr) = Total Volume (ml) ÷ Time (hours)
Example: A doctor prescribes 1,000 ml of Normal Saline to be infused over 8 hours.
Volume = 1,000 ml
Time = 8 hours
Calculation: 1,000 ÷ 8 = 125 ml/hr
Calculating Drip Rate (gtt/min)
If an electronic pump is not available, nurses must set the flow rate manually by counting drops per minute (gtt/min) in the drip chamber. To calculate this, you must know the Drop Factor of the tubing being used. The drop factor is printed on the tubing package and represents how many drops it takes to equal 1 milliliter.
Drip Rate (gtt/min) = (Total Volume (ml) × Drop Factor (gtt/ml)) ÷ Time (minutes)
Alternatively, if you already know the ml/hr:
Drip Rate (gtt/min) = (ml/hr × Drop Factor) ÷ 60
Common Drop Factors
Tubing comes in two main categories:
Macrodrip (Standard): Used for general adult IV therapy. Common factors are 10, 15, or 20 gtt/ml.
Microdrip (Pediatric): Used for precise small volumes, typically pediatrics or potent medications. Standard factor is 60 gtt/ml.
Clinical Tips
Always double-check your math. In many hospitals, high-alert medications require a second nurse to verify the flow rate calculation. When calculating gtt/min manually, always round to the nearest whole number, as it is impossible to count a fraction of a drop.