Calculator Outputs Explained

The tool provides two primary outputs depending on the user's goal:

• Infusion Rate (mL/hr): When you input the patient's weight and a desired dose (in mcg/kg/min), the calculator computes the exact rate at which the infusion pump should be set to deliver that dose.
• Current Dose (mcg/kg/min): If a patient is already on an infusion, you can input their weight and the current pump rate (in mL/hr) to calculate the precise dose they are receiving. This is essential for clinical documentation and dose titration.
• Dose Titration Table: When calculating an infusion rate, the tool also generates a helpful table showing the corresponding pump rates for doses slightly above and below the target. This supports rapid bedside adjustments.

How to Use the Calculator

To ensure accurate results, follow these steps:

1. Enter Patient Weight: Input the patient's weight. You can toggle between kilograms (kg) and pounds (lbs); the tool will automatically perform the conversion. Use actual body weight unless institutional protocol dictates otherwise.
2. Select Drug Concentration: Choose from the list of standard epinephrine concentrations (e.g., 4 mg in 250 mL). If your institution uses a different mixture, select "Custom" and enter the total amount of epinephrine (mg) and the total fluid volume (mL) in the helper fields.
3. Choose a Calculation Mode:
   • To find the pump rate, enter the Desired Dose in mcg/kg/min.
   • To find the current dose, enter the Current Infusion Rate in mL/hr.
4. Review Results: The calculator will instantly display the calculated rate or dose, along with a summary and a titration table if applicable. Always double-check the inputs and the final result against institutional protocols and with a second clinician.

Dosing Overview

Epinephrine dosing is highly individualized and titrated to a specific hemodynamic target (e.g., mean arterial pressure). Dosing varies significantly by indication:

• Septic Shock: Often initiated at 0.01 to 0.05 mcg/kg/min and titrated upwards, typically within a range of 0.05 to 2 mcg/kg/min. It is generally used as a second-line agent after norepinephrine.
• Post-Cardiac Arrest (ROSC): Dosing aims to support blood pressure and cardiac output, commonly starting around 0.1 to 0.5 mcg/kg/min.
• Anaphylaxis: For severe cases refractory to intramuscular epinephrine, an IV infusion may be started at a low dose, such as 0.05 to 0.1 mcg/kg/min, with careful titration.
• Bradycardia: For symptomatic bradycardia unresponsive to atropine or pacing, an infusion can be started at 2 to 10 mcg/min (note: this is not weight-based) and titrated to patient response.

Continuous monitoring of heart rate, blood pressure (ideally via an arterial line), and EKG is mandatory during administration.

Managing Infusion Bags and Titration

When an epinephrine infusion bag is running low, a new bag should be prepared and ready to be switched promptly to avoid any interruption in therapy. This process is known as "back-priming" or using a "quick-set" change method to minimize hemodynamic instability.

Titration should be performed systematically based on patient response and pre-defined clinical targets. Changes should be made in small increments (e.g., 0.01-0.03 mcg/kg/min) with sufficient time (e.g., 3-5 minutes) between adjustments to assess the effect.

Managing Infusion Interruptions

Due to its very short half-life (approximately 2-3 minutes), any interruption in an epinephrine infusion will lead to a rapid loss of its therapeutic effect. If the infusion is stopped for any reason (e.g., transport, line occlusion), the patient's hemodynamic status must be closely monitored and the infusion restarted as quickly as possible at the previously effective rate, followed by re-titration.

Safety Alerts

Epinephrine is a high-alert medication with significant risks if administered incorrectly.

• Extravasation: Epinephrine is a potent vasoconstrictor and can cause severe tissue necrosis if it leaks out of the vein. It should be administered through a central venous catheter whenever possible. If extravasation is suspected, stop the infusion and follow institutional protocol, which may include local infiltration of phentolamine.
• Calculation Verification: All dose calculations must be independently double-checked by a second qualified healthcare professional before administration or any rate change.
• Adverse Effects: Monitor for tachycardia, arrhythmias (including ventricular tachycardia), hypertension, hyperglycemia, and increased lactate levels.
• Drug Incompatibilities: Do not administer with alkaline solutions (e.g., sodium bicarbonate), as this will degrade the epinephrine.

Frequently Asked Questions

Why does the calculator require either a 'Desired Dose' or 'Infusion Rate', but not both?

The calculator has two distinct functions. It either calculates the infusion rate *from* a desired dose, or it calculates the current dose *from* a known infusion rate. Entering both would create a conflict, so you must provide one to calculate the other.

How does the 'Custom' concentration option work?

This feature lets you use the calculator even if your IV bag concentration isn't listed. You enter the total drug amount (in milligrams) and the total fluid volume (in milliliters) of your IV bag into the helper fields. The tool then calculates the concentration in mcg/mL to use in its primary calculation.

What is the standard concentration for an epinephrine drip?

Concentrations vary by institution. Common "standard" concentrations include 1 mg in 250 mL (4 mcg/mL), 2 mg in 250 mL (8 mcg/mL), and 4 mg in 250 mL (16 mcg/mL). The 16 mcg/mL concentration is often used in adult ICUs to provide a more concentrated solution, reducing the fluid load.

Should I use actual or ideal body weight?

For most vasopressor dosing, actual body weight is typically used. However, in patients with severe obesity, some institutional protocols may call for an adjusted or ideal body weight. Always follow your local hospital's policy.

Why is a central line preferred for epinephrine infusions?

A central venous catheter is strongly recommended because epinephrine is a potent vesicant. If it leaks from a peripheral IV into the surrounding tissue (extravasation), it can cause severe vasoconstriction, leading to tissue damage and necrosis. A central line delivers the drug into a large, high-flow vein, minimizing this risk.

What does the titration table show?

When you calculate an infusion rate from a desired dose, the titration table provides a quick reference for small dose adjustments. It shows the mL/hr rates required for doses slightly higher and lower than your target, helping with rapid bedside changes without needing to re-calculate each time.

Can this calculator be used for push-dose pressors?

No. This tool is designed exclusively for continuous intravenous infusions. Push-dose epinephrine is prepared differently (typically 10 mcg/mL) and administered intermittently in small boluses (e.g., 0.5-2 mL every 1-5 minutes). Do not use this calculator for that purpose.

How often should I monitor the patient on an epinephrine infusion?

Continuous monitoring is required. This includes continuous EKG, pulse oximetry, and invasive arterial blood pressure monitoring. Hemodynamic parameters should be assessed and documented at least every 15 minutes after initiation and with every dose change, and then hourly once stable.

References

1. U.S. Food and Drug Administration (FDA). ADRENALIN (epinephrine injection) prescribing information. Silver Spring, MD: FDA; 2016.
2. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S366-S468.
3. Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Critical Care Medicine. 2021;49(11):e1063-e1143.
4. Moroz V, An AY. The Role of Vasopressors in the Management of Septic Shock. Journal of Clinical Medicine. 2022;11(6):1668.