Constant Rate Infusion Calculator

Constant Rate Infusion (CRI) Calculator

Calculation Results

Required Infusion Rate: 0 mL/hr

Total Drug Dose: 0 µg/min

function calculateCRIDose() { var weight = parseFloat(document.getElementById('patientWeight').value); var dosage = parseFloat(document.getElementById('dosageRate').value); var concentration = parseFloat(document.getElementById('drugConc').value); var maintenanceFluid = parseFloat(document.getElementById('fluidRate').value); if (isNaN(weight) || isNaN(dosage) || isNaN(concentration) || weight <= 0 || dosage <= 0 || concentration 0) { var ratio = mlPerHour / maintenanceFluid; mixingText = "Note: To deliver this dose within your set fluid rate of " + maintenanceFluid + " mL/hr, ensure the drug concentration in the bag is adjusted accordingly."; } else { mixingText = "This calculation assumes the drug is administered via a syringe pump at the calculated rate."; } document.getElementById('mixingInstructions').innerText = mixingText; document.getElementById('cri-results').style.display = 'block'; }

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Understanding Constant Rate Infusion (CRI)

Constant Rate Infusion (CRI) is a method of drug administration where a medication is delivered intravenously at a continuous, steady rate. Unlike bolus injections, which cause "peaks and valleys" in blood plasma concentration, a CRI maintains a steady-state concentration, providing consistent analgesia or therapeutic effect.

Key Components of CRI Calculation

• Patient Weight: Necessary to calculate the metabolic demand for the drug.
• Dosage Rate (µg/kg/min): The specific amount of drug required per unit of weight per minute. Common for potent drugs like Fentanyl or Dopamine.
• Drug Concentration: Usually expressed in mg/mL on the vial. Our calculator automatically converts this to micrograms (µg) for precision.

Practical Example

Suppose you have a canine patient weighing 20 kg. You wish to administer a Fentanyl CRI at a dose of 0.1 µg/kg/min. Your Fentanyl vial concentration is 0.05 mg/mL.

Step-by-Step Logic:

1. Calculate µg per minute: 20kg × 0.1 µg/kg/min = 2 µg/min.
2. Calculate µg per hour: 2 µg/min × 60 min = 120 µg/hr.
3. Convert vial concentration: 0.05 mg/mL = 50 µg/mL.
4. Calculate mL per hour: 120 µg/hr ÷ 50 µg/mL = 2.4 mL/hr.

Commonly Used Drugs for CRI

Drug	Typical Dose Range	Primary Use
Lidocaine	25–50 µg/kg/min	Analgesia / Anti-arrhythmic
Ketamine	2–10 µg/kg/min	NMDA Antagonist / Analgesia
Dopamine	5–15 µg/kg/min	Blood Pressure Support

Safety Considerations

Always double-check your math when dealing with potent medications. CRI delivery is best managed with a syringe pump or an infusion pump to ensure accuracy. If you are adding the drug to a larger fluid bag (e.g., 1L of Saline), ensure the bag is clearly labeled with the drug name, the amount added, the date, and the calculated drip rate.