Complete Calculation for Noradrenaline (Norepinephrine) Infusion

Noradrenaline (Norepinephrine) is a vasopressor commonly used in septic shock, cardiogenic shock, and severe hypotension. It is a high-alert ICU drug, so precise calculation is essential.

 

🔹 Clinical Scenario

Doctor’s Order: Noradrenaline 0.1 mcg/kg/min
Patient Weight: 70 kg
Available Preparation: 4 mg Noradrenaline in 50 mL Normal Saline

We will calculate:

1.     Required dose per minute

2.     Required dose per hour

3.     Drug concentration

4.     Final infusion rate (mL/hour)

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Step 1️: Calculate the required dose per Minute

Now substitute values:

= 0.1 × 70

= 7 mcg/min

✅ Required dose = 7 mcg/min

 

Step 2️: Convert mcg/min to mcg/hour

7 × 60 = 420 mcg/hour

✅ Required dose = 420 mcg/hour

 

Step 3️: Convert Available Drug to mcg

Available: 4 mg in 50 mL

Convert mg → mcg:

4 mg = 4000 mcg

So:

4000 mcg in 50 mL

 

Step 4️: Calculate Concentration

= 4000 ÷ 50

= 80 mcg/mL

✅ Concentration = 80 mcg/mL

 

Step 5️: Calculate mL/hour

= 420 ÷ 80

= 5.25 mL/hour

 

✅ Final Answer:

Set infusion pump at 5.25 mL/hour

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🔎 Quick Shortcut Formula (For Exams & ICU)

mL/hr=(Dose×Weight×60÷Totalmcginbag)×Totalvolume

Where:

• Dose = mcg/kg/min
• Weight = kg
• Total mcg in bag = mg × 1000

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🧮 Practice Example 2

Order: 0.05 mcg/kg/min

Weight: 60 kg

Available: 8 mg in 100 mL

Step 1:

0.05 × 60 = 3 mcg/min

Step 2:

3 × 60 = 180 mcg/hr

Step 3:

8 mg = 8000 mcg

Concentration:

8000 ÷ 100 = 80 mcg/mL

Step 4:

180 ÷ 80 = 2.25 mL/hr

✅ Set pump at 2.25 mL/hour

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📊 Common Noradrenaline ICU Dilutions

Dose Range	Typical Starting Dose
Septic shock	0.05–0.3 mcg/kg/min
Severe shock	Up to 1 mcg/kg/min (ICU monitored)

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⚠️ Important Safety Points

• Always use an infusion pump.
• Prefer central venous line.
• Monitor BP continuously (arterial line preferred).
• Monitor urine output.
• Watch for extravasation (risk of tissue necrosis).
• Double-check calculation with another nurse.

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