⚠️ DISCLAIMER: This tool is for educational and verification purposes only. It should not replace professional clinical judgment or institutional protocols. Always double-check calculations before administering medication.
Understanding mcg/kg/min Infusion Calculations
In critical care settings, precise medication delivery is vital for patient stability. Many vasoactive drugs, sedatives, and anti-arrhythmics are dosed based on the patient's body weight and time, typically expressed as micrograms per kilogram per minute (mcg/kg/min).
Calculating the correct flow rate ensures that the patient receives the exact therapeutic dose required. This calculator assists healthcare professionals, nursing students, and paramedics in converting a weight-based dose into a programmable pump rate (mL/hr) or a manual drip rate (gtt/min).
The Calculation Formula
To determine the infusion rate manually, you can use dimensional analysis. The process involves three main steps: determining the concentration, calculating the per-minute requirement, and converting to flow rate.
Step 1: Determine Concentration (mcg/mL)
Concentration = (Total Drug mg × 1000) / Total Volume mL
Patient Weight (kg): The actual body weight of the patient. For some medications, ideal body weight may be used depending on hospital protocol.
Desired Dose (mcg/kg/min): The prescribed amount of drug to be delivered every minute for every kilogram of body weight.
Total Drug Amount (mg): The total mass of the medication added to the IV bag. Note that this calculator converts mg to mcg automatically (1 mg = 1000 mcg).
Total Volume (mL): The final volume of the solution in the IV bag (e.g., 250mL, 500mL).
Drop Factor (gtt/mL): The calibration of the IV tubing used. Microdrip tubing is usually 60 gtt/mL, while macrodrip tubing is typically 10, 15, or 20 gtt/mL.
Common Medications Dosed in mcg/kg/min
Several high-alert medications utilize this dosing structure due to their potent effects and short half-lives:
Dopamine: Often used for hemodynamic support in shock.
Dobutamine: Used to treat heart failure and cardiogenic shock.
Norepinephrine (Levophed): A vasoconstrictor used to raise blood pressure.
Nitroprusside: Used for rapid reduction of blood pressure in hypertensive crises.
Clinical Safety Tips
When administering weight-based infusions, always adhere to the "Rights of Medication Administration." Ensure the patient's weight is current and accurate. Double-check the concentration on the IV bag, as standard concentrations can vary between institutions. If utilizing a smart pump, ensure the correct drug library profile is selected to prevent programming errors.
function calculateInfusion() {
// 1. Get Input Values
var weight = parseFloat(document.getElementById('patientWeight').value);
var dose = parseFloat(document.getElementById('desiredDose').value);
var drugMg = parseFloat(document.getElementById('drugAmount').value);
var volume = parseFloat(document.getElementById('totalVolume').value);
var dropFactor = parseFloat(document.getElementById('dropFactor').value);
// 2. Validate Inputs
if (isNaN(weight) || isNaN(dose) || isNaN(drugMg) || isNaN(volume) || isNaN(dropFactor)) {
alert("Please fill in all fields with valid numbers.");
return;
}
if (volume === 0) {
alert("Volume cannot be zero.");
return;
}
// 3. Perform Calculations
// Convert Drug Amount from mg to mcg
var totalDrugMcg = drugMg * 1000;
// Calculate Concentration (mcg per mL)
var concentration = totalDrugMcg / volume;
// Calculate Total Dose Needed Per Minute (mcg/min)
var totalDosePerMin = dose * weight;
// Calculate Flow Rate in mL/min
var mlPerMin = totalDosePerMin / concentration;
// Calculate Hourly Rate (mL/hr)
var mlPerHour = mlPerMin * 60;
// Calculate Drops Per Minute (gtt/min)
var dropsPerMin = mlPerMin * dropFactor;
// 4. Update UI
// Display Section
document.getElementById('resultsSection').style.display = 'block';
// Update Text Content
// Rounding to 1 decimal place for pump rate, nearest whole number for drops
document.getElementById('resMlPerHour').innerHTML = mlPerHour.toFixed(1) + " mL/hr";
document.getElementById('resDropsPerMin').innerHTML = Math.round(dropsPerMin) + " gtt/min";
// Show concentration for verification
document.getElementById('resConcentration').innerHTML = concentration.toFixed(0) + " mcg/mL";
}