function calculateDopamineRate() {
var weightInput = document.getElementById('ptWeight').value;
var unit = document.getElementById('weightUnit').value;
var doseInput = document.getElementById('desiredDose').value;
var drugAmtInput = document.getElementById('drugAmt').value;
var bagVolInput = document.getElementById('bagVol').value;
var dropFactor = parseFloat(document.getElementById('dropFactor').value);
var errorBox = document.getElementById('calcError');
var resultBox = document.getElementById('calcResult');
// Validation
if (weightInput === "" || doseInput === "" || drugAmtInput === "" || bagVolInput === "") {
errorBox.style.display = "block";
resultBox.style.display = "none";
return;
}
var weight = parseFloat(weightInput);
var dose = parseFloat(doseInput);
var drugAmt = parseFloat(drugAmtInput);
var bagVol = parseFloat(bagVolInput);
if (isNaN(weight) || isNaN(dose) || isNaN(drugAmt) || isNaN(bagVol) || weight <= 0 || bagVol <= 0) {
errorBox.style.display = "block";
resultBox.style.display = "none";
return;
}
errorBox.style.display = "none";
// Convert lbs to kg if necessary
var weightKg = weight;
if (unit === 'lbs') {
weightKg = weight / 2.20462;
}
// Calculate Concentration (mcg/mL)
// Convert mg to mcg by multiplying by 1000
var concentrationMcgMl = (drugAmt * 1000) / bagVol;
// Calculate Total Dose Needed per Minute (mcg/min)
var totalDosePerMin = dose * weightKg;
// Calculate mL/hr
// (mcg/min * 60 min/hr) / concentration(mcg/mL)
var mlPerHour = (totalDosePerMin * 60) / concentrationMcgMl;
// Calculate gtt/min (Drip Rate)
// (mL/hr * drop factor) / 60 min
var gttPerMin = (mlPerHour * dropFactor) / 60;
// Display Results
document.getElementById('resConcentration').innerText = Math.round(concentrationMcgMl) + " mcg/mL";
document.getElementById('resWeightKg').innerText = weightKg.toFixed(2) + " kg";
document.getElementById('resTotalDose').innerText = totalDosePerMin.toFixed(1) + " mcg/min";
// Pump setting usually allows 1 decimal place
document.getElementById('resMlHr').innerText = mlPerHour.toFixed(1) + " mL/hr";
// Drops must be whole numbers
document.getElementById('resGttMin').innerText = Math.round(gttPerMin) + " gtt/min";
resultBox.style.display = "block";
}
Understanding Dopamine Infusion Calculations
Calculating the correct drip rate for dopamine is a critical skill in emergency and critical care nursing. Dopamine is a potent vasoactive agent used to treat shock, hypotension, and low cardiac output. Because its therapeutic window is narrow and dose-dependent, precision in calculation is vital for patient safety.
The Calculation Formula
The Dopamine Drip Rate Calculator uses standard pharmacokinetic formulas to determine the flow rate. The calculation involves three main steps:
Step 1: Determine Concentration. Convert the total drug amount from milligrams (mg) to micrograms (mcg) and divide by the bag volume. Formula: (Drug mg × 1000) / Volume mL = Concentration (mcg/mL)
Step 2: Calculate Total Dose per Minute. Multiply the patient's weight in kg by the ordered dose. Formula: Weight (kg) × Dose (mcg/kg/min) = Total mcg/min
Step 3: Calculate Infusion Rate (mL/hr). Determine how many milliliters are needed per hour to deliver the required micrograms. Formula: (Total mcg/min × 60 min) / Concentration (mcg/mL) = Rate (mL/hr)
Standard Dopamine Concentrations
While concentrations can vary by pharmacy and hospital protocol, the most common standard preparations ("Pre-mixed bags") found in clinical settings are:
400 mg in 250 mL D5W (1600 mcg/mL)
800 mg in 250 mL D5W (3200 mcg/mL)
800 mg in 500 mL D5W (1600 mcg/mL)
Always verify the concentration listed on the IV bag against the calculator input to ensure accuracy.
Dose-Dependent Effects
Dopamine is unique because its physiological effects change based on the dosage range administered:
Low Dose (Renal/Mesenteric): 0.5 – 2 mcg/kg/min. Historically thought to vasodilate renal arteries and increase urine output, though clinical efficacy is debated.
Intermediate Dose (Inotropic): 2 – 10 mcg/kg/min. Stimulates Beta-1 receptors, increasing cardiac contractility and heart rate. Used for heart failure and bradycardia.
High Dose (Vasopressor): 10 – 20 mcg/kg/min. Stimulates Alpha receptors causing systemic vasoconstriction. Used to increase blood pressure in shock states.
Clinical Considerations & Safety
Extravasation Risk: Dopamine is a vesicant. If it leaks into surrounding tissue, it can cause severe necrosis. It should ideally be administered via a Central Venous Catheter (CVC). If peripheral administration is necessary, use a large vein and monitor the site frequently.
Weaning: Never stop a dopamine infusion abruptly. It must be titrated down gradually to prevent rebound hypotension.
Medical Disclaimer: This calculator is intended for educational and verification purposes only. It should not replace clinical judgment or institutional protocols. Always double-check calculations independently and verify pump settings with a second licensed practitioner before administration.