:root {
–primary-color: #0073e6;
–secondary-color: #f0f4f8;
–text-color: #333;
–border-color: #ddd;
–accent-color: #005bb5;
–error-color: #d32f2f;
–success-color: #2e7d32;
}
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: var(–text-color);
margin: 0;
padding: 20px;
}
.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
background: #fff;
border: 1px solid var(–border-color);
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
overflow: hidden;
}
.calc-header {
background: var(–primary-color);
color: #fff;
padding: 20px;
text-align: center;
}
.calc-header h2 {
margin: 0;
font-size: 1.5rem;
}
.calc-body {
padding: 25px;
background-color: var(–secondary-color);
}
.input-group {
margin-bottom: 20px;
background: #fff;
padding: 15px;
border-radius: 6px;
border: 1px solid var(–border-color);
}
.input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: var(–text-color);
}
.input-group input {
width: 100%;
padding: 10px;
font-size: 16px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.input-group small {
display: block;
color: #666;
margin-top: 5px;
font-size: 0.85rem;
}
button.calc-btn {
width: 100%;
background-color: var(–primary-color);
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
}
button.calc-btn:hover {
background-color: var(–accent-color);
}
#result-area {
margin-top: 25px;
padding: 20px;
background-color: white;
border-radius: 6px;
border-left: 5px solid var(–primary-color);
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
align-items: center;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
font-weight: 600;
color: #555;
}
.result-value {
font-size: 1.4rem;
font-weight: bold;
color: var(–primary-color);
}
.error-msg {
color: var(–error-color);
text-align: center;
margin-top: 10px;
font-weight: bold;
display: none;
}
.content-section {
margin-top: 40px;
max-width: 800px;
margin-left: auto;
margin-right: auto;
}
.content-section h3 {
color: var(–primary-color);
border-bottom: 2px solid var(–border-color);
padding-bottom: 10px;
}
.formula-box {
background: #f8f9fa;
padding: 15px;
border-left: 4px solid #28a745;
font-family: monospace;
margin: 15px 0;
overflow-x: auto;
}
.example-box {
background: #fff3cd;
padding: 15px;
border: 1px solid #ffeeba;
border-radius: 4px;
color: #856404;
}
@media (max-width: 600px) {
.result-row {
flex-direction: column;
align-items: flex-start;
}
.result-value {
margin-top: 5px;
}
}
How to Calculate Infusion Rate (mcg/kg/min to mL/hr)
In critical care and emergency medicine, many vasoactive medications (such as Dopamine, Dobutamine, and Norepinephrine) are dosed based on the patient's body weight. The order is typically given in micrograms per kilogram per minute (mcg/kg/min), but IV infusion pumps are programmed in milliliters per hour (mL/hr). Accurate conversion is vital for patient safety.
The Conversion Formula
To convert a weight-based dose into a flow rate, you must account for the drug concentration, the patient's weight, and time unit conversions (minutes to hours and micrograms to milligrams).
Flow Rate (mL/hr) =
[ Dose (mcg/kg/min) × Weight (kg) × 60 min/hr ]
————————————————
[ Concentration (mg/mL) × 1000 mcg/mg ]
Alternatively, the calculation can be performed in steps:
- Calculate Concentration: Divide the total drug amount (mg) by the total volume (mL).
- Calculate Total Hourly Dose: Multiply the dose (mcg) by weight (kg) and by 60 (minutes).
- Convert Units: Divide the result by 1000 to convert micrograms to milligrams.
- Determine Flow Rate: Divide the hourly dose (mg/hr) by the concentration (mg/mL).
Example Calculation
Scenario: A physician orders Dopamine at 5 mcg/kg/min for a patient weighing 80 kg. The pharmacy supplies a bag containing 400 mg of Dopamine in 250 mL of D5W.
Step 1: Concentration
400 mg ÷ 250 mL = 1.6 mg/mL
Step 2: Total Dose Required
5 mcg × 80 kg × 60 min = 24,000 mcg/hr
Step 3: Convert to mg
24,000 mcg ÷ 1000 = 24 mg/hr
Step 4: Flow Rate
24 mg/hr ÷ 1.6 mg/mL = 15 mL/hr
Result: Set the IV pump to 15 mL/hr.
Common Medications Using This Formula
This calculation is frequently used for titratable drips in the ICU, including:
- Dopamine: Often used for hypotension and bradycardia.
- Dobutamine: Used for heart failure and cardiogenic shock.
- Norepinephrine (Levophed): Used for severe hypotension and septic shock.
- Epinephrine: Used for anaphylaxis and shock states.
- Nitroprusside: Used for hypertensive emergencies.
Clinical Safety Tips
Always double-check your calculations, especially for high-alert medications. Many modern "smart pumps" have dose-error reduction systems (DERS) that perform this math automatically, but understanding the manual calculation is essential for verification and during equipment failure. Ensure you are using the correct units (mg vs mcg) as this is the most common source of calculation errors.
function calculateFlowRate() {
// 1. Get DOM elements
var weightInput = document.getElementById("weight");
var doseInput = document.getElementById("dose");
var drugAmountInput = document.getElementById("drugAmount");
var volumeInput = document.getElementById("volume");
var resultArea = document.getElementById("result-area");
var errorMsg = document.getElementById("error-message");
var finalRateDisplay = document.getElementById("finalRate");
var finalConcDisplay = document.getElementById("finalConcentration");
var finalDoseHourDisplay = document.getElementById("finalDoseHour");
// 2. Parse values
var weight = parseFloat(weightInput.value);
var dose = parseFloat(doseInput.value);
var drugAmount = parseFloat(drugAmountInput.value);
var volume = parseFloat(volumeInput.value);
// 3. Validation
if (isNaN(weight) || weight <= 0 ||
isNaN(dose) || dose < 0 ||
isNaN(drugAmount) || drugAmount <= 0 ||
isNaN(volume) || volume <= 0) {
resultArea.style.display = "none";
errorMsg.style.display = "block";
return;
}
// Hide error if valid
errorMsg.style.display = "none";
// 4. Calculation Logic
// Step A: Calculate Concentration in mg/mL
// Concentration = Total mg / Total mL
var concentrationMgPerMl = drugAmount / volume;
// Step B: Calculate Total Dose per Hour in mg
// (mcg/kg/min * weight * 60 min) / 1000 (to convert mcg to mg)
var doseMgPerHour = (dose * weight * 60) / 1000;
// Step C: Calculate Flow Rate in mL/hr
// mL/hr = (mg/hr) / (mg/mL)
var flowRateMlHr = doseMgPerHour / concentrationMgPerMl;
// 5. Display Results
// Rounding logic: Pump rates usually allow 1 decimal place, sometimes 2.
// We will show 1 decimal place for practicality.
finalRateDisplay.innerHTML = flowRateMlHr.toFixed(1) + " mL/hr";
finalConcDisplay.innerHTML = concentrationMgPerMl.toFixed(3) + " mg/mL";
finalDoseHourDisplay.innerHTML = doseMgPerHour.toFixed(2) + " mg/hr";
resultArea.style.display = "block";
}