Learning to calculate norepinephrine dose for ICU patients and posology and dose of adrenaline for anaphylaxis, anaphylactic shock and severe allergy.

If you work in the healthcare field and deal with medication administration, you know how crucial it is to accurately calculate the dosage of drugs such as noradrenaline and adrenaline, which are often used in critically ill patients, sometimes intubated in the intensive care unit (ICU). Let's review this process below, which is of great practical importance, as errors can have serious consequences for patient's health. That's why we developed the Drug Infusion app, which simplifies and automatically calculates medication dosage, and is available on the Apple Store and Google Play.

With the Drug Infusion app, you will have access to a complete and reliable tool that allows for automatic and precise dose calculations based on your patient's weight for the most commonly used medications in the ICU, such as epinephrine, noradrenaline, dobutamine, intubation drugs, among others.

Our calculator also allows you to convert units of measurement, such as mL/h to mcg/Kg/min, further simplifying the process. With just a few clicks, you will obtain the necessary values to safely and effectively administer the medication.

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Noradrenaline vs. Adrenaline: Know the Differences, Uses and Functions

Noradrenaline (also known as norepinephrine) and adrenaline (also known as epinephrine) are medications that have similar chemical structures but have different biological effects and are used to treat different conditions. Here are some indications for the use of each of them.

Indications for the use of Adrenaline:

• Hemodynamic support in cardiac arrest
• Anaphylactic reactions (for example, anaphylactic shock)
• Severe asthma attacks
• Control of minor cutaneous hemorrhages

Indications for the use of Noradrenaline:

• Blood pressure control in certain acute hypotensive states
• Arterial hypotension due to its vasoconstrictor effect
• Septic shock

Ampolas de Adrenalina e Noradrenalina e Diluição

Noradrenaline has different ampoules, and the dosage calculation should be based on the norepinephrine base, which can be found in the medication's package insert. The most common ampoule for noradrenaline contains 1 mg/mL of norepinephrine base with a volume of 4mL. In the case of adrenaline, the most common ampoule contains 1 mL at a concentration of 1 mg/mL and is usually used undiluted for cases of anaphylaxis. Both medications should be stored away from light (as they are photosensitive drugs) to preserve their pharmacological properties.

The most commonly used noradrenaline solutions in clinical practice are prepared with the following dilutions:

• 05 ampoules of 4 mL diluted in 180 mL of 5% glucose solution.
• 10 ampoules of 4 mL diluted in 160 mL of 5% glucose solution (known as double-strength solution).

Next, we will proceed with the calculations for the concentration of noradrenaline using the above dilutions and how to calculate the dose for a hypothetical patient.

Calculation of Diluted Noradrenaline Solution Concentration

Calculation of the total volume of noradrenaline ampoules:

Calculation of the amount of norepinephrine base: 1 mg/mL X 4 mL X 5 ampoules = 20 mg.

Calculation of the concentration of the diluted solution with a volume of 180 mL + 20 mL:

Performing the same calculations for the double-strength solution, the concentration of norepinephrine base is 0.2 mg/mL.

Calculation of Noradrenaline Dose

The dose of norepinephrine base for septic shock is 0.01 to 3.3 mcg/kg/min in continuous infusion using an infusion pump. Let's calculate the therapeutic range for an 80 kg patient below.

Calculation of the Minimum Dose of Noradrenaline

For an 80 kg patient, the minimum dose would be 80 X 0.01 mcg/min = 0.8 mcg/min or 60 x 0.8 mcg/h = 48 mcg/h. Since the noradrenaline solution contains 0.1 mg/mL of norepinephrine base, which is equivalent to 100 mcg/mL, we have:

Note: Some references determine the initial dose of norepinephrine as 0.05 mcg/kg/min, which is five times higher than the initial dose calculated above, equivalent to 5 x 0.48 mL/h = 2.4 mL/h.

Calculation of the recommended maximum dose of norepinephrine

For an 80 kg patient, it would require 80 X 3.3 mcg/min = 264 mcg/min or 60 x 264 mcg/h = 15,840 mcg/h. Since the norepinephrine solution contains 0.1 mg/mL of norepinephrine base, which is equal to 100 mcg/mL, we have:

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Calculation of adrenaline dose for anaphylaxis and anaphylactic shock and route of administration

The dose of adrenaline for anaphylaxis and anaphylactic shock is 0.3 to 0.5 mg, with a preferred dose of 0.5 mg in patients weighing over 50 kg, which can be repeated every 5 to 15 minutes. The recommended route of administration for adrenaline in cases of anaphylaxis or anaphylactic shock is intramuscular, with administration in the anterolateral aspect of the thigh. For example, in the case of an 80 kg patient, the following calculations would be performed, knowing that the adrenaline ampoule has a concentration of 1 mg/mL with a volume of 1 mL:

Thus, the adrenaline dose for anaphylaxis for this patient is 0.5 mL per dose, using the 1 mg/mL ampoule via intramuscular route.

Calculation of subcutaneous adrenaline dose for severe allergies

The dose of adrenaline for severe allergic reactions is 0.3 to 0.5 mg via subcutaneous route. The dose of 0.5 mg should be used mainly in patients with more severe reactions or weighing over 60 kg and can be repeated every 5 to 15 minutes. In the case of an 80 kg patient, the same calculations as in the previous section would be performed, and therefore 0.5 mL of the adrenaline ampoule could be used via the subcutaneous route.

BONUS: Calculation of noradrenaline from mL/h to mcg/kg/min

We often encounter a patient who is already receiving noradrenaline and would like to know how many mcg/kg/min they are receiving. In this section, I intend to show you how to perform this calculation.

We will use a hypothetical situation of an 80 kg patient who is receiving a solution of 100 mcg/mL of noradrenaline base at a rate of 100 mL/h, and we would like to know the corresponding value in mcg/kg/min.

To convert mcg/h to mcg/min, divide by 60, resulting in 10,000 mcg / 60 = 166.67 mcg/min.

Now, we divide by the patient's weight to find the value in mcg/kg/min. Thus, 166.67 mcg / 80 kg = 2.08 mcg/kg/min. Therefore, an 80 kg patient receiving the noradrenaline solution at 100 mL/h would be receiving the equivalent of 2.08 mcg/kg/min.

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