InfusionFox
Vasopressors & Inotropes

Norepinephrine CRI

Vasopressor CRI for dogs and cats. Used to restore mean arterial pressure in vasodilatory hypotension once volume resuscitation is adequate, including inhalant-induced anesthetic hypotension and septic or other distributive shock. High-alert medication; continuous BP and ECG monitoring required given dose-related arrhythmia and peripheral ischemia risk.

Stock: 1 mg/mL (1000 µg/mL), 4 mL vial (4 mg)
How this calculator works

Enter the patient's weight and dose. The calculator picks a bag concentration that keeps the pump in its accurate range (≥ 2 mL/hr for most volumetric pumps), and a bag size that uses one full vial of stock where possible.

Both selections show a suggested tag that updates as you change the patient inputs. Click any tab to override; the override sticks for the rest of the session, and a notice will appear if your choice doesn't match the patient.

If even the most dilute preparation gives an unworkable rate (very small patient on a low dose), switch to Advanced: target pump rate; you pick the rate you want, the calculator derives the bag concentration to deliver it.

Typical range: 0.05–2.0 ug/kg/min (dogs and cats)
250 mL preparation suggested · uses one full vial
Draw 4 mL of 1 mg/mL norepinephrine stock (1 vial = 4 mg)
Add to 250 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 16 µg/mL norepinephrine in 250 mL
500 mL preparation
Draw 8 mL of 1 mg/mL norepinephrine stock (2 vials = 8 mg)
Add to 500 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 16 µg/mL norepinephrine in 500 mL
1 L preparation
Draw 16 mL of 1 mg/mL norepinephrine stock (4 vials = 16 mg)
Add to 1 L bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 16 µg/mL norepinephrine in 1 L
250 mL preparation
Draw 2 mL of 1 mg/mL norepinephrine stock (half-vial; discard the rest = 2 mg)
Add to 250 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 8 µg/mL norepinephrine in 250 mL
500 mL preparation suggested · uses one full vial
Draw 4 mL of 1 mg/mL norepinephrine stock (1 vial = 4 mg)
Add to 500 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 8 µg/mL norepinephrine in 500 mL
1 L preparation
Draw 8 mL of 1 mg/mL norepinephrine stock (2 vials = 8 mg)
Add to 1 L bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 8 µg/mL norepinephrine in 1 L
250 mL preparation
Draw 1 mL of 1 mg/mL norepinephrine stock (quarter-vial; discard the rest = 1 mg)
Add to 250 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 4 µg/mL norepinephrine in 250 mL
500 mL preparation
Draw 2 mL of 1 mg/mL norepinephrine stock (half-vial; discard the rest = 2 mg)
Add to 500 mL bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 4 µg/mL norepinephrine in 500 mL
1 L preparation suggested · uses one full vial
Draw 4 mL of 1 mg/mL norepinephrine stock (1 vial = 4 mg)
Add to 1 L bag of 5% dextrose, or 5% dextrose with 0.9% NaCl
Final 4 µg/mL norepinephrine in 1 L
Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

Norepinephrine CRI is dosed in µg/kg/min. To convert a per-minute dose into a per-hour CRI rate, multiply by 60. The full formula:

$$\text{mL/hr} = \frac{\text{weight}_{\text{kg}} \times \text{dose}_{\mu g/kg/min} \times 60}{\text{concentration}_{\mu g/mL}}$$

Why the 60? The patient's weight (kg) times the dose (µg per kg per minute) gives micrograms per minute. Multiplying by 60 converts to micrograms per hour. Dividing by the concentration (µg per mL of the prepared CRI) yields mL per hour.

In target-pump-rate mode the pump rate is fixed by the clinician and the bag concentration is the unknown. The preparation runs in three steps.

Step 1: bag concentration

Same numerator as standard-bag mode (the total drug delivered per hour for this patient), but divided by the chosen pump rate instead of by a chosen bag concentration:

$$\text{bag concentration}_{\mu g/mL} = \frac{\text{weight}_{\text{kg}} \times \text{dose}_{\mu g/kg/min} \times 60}{\text{pump rate}_{\text{mL/hr}}}$$

Step 2: total drug in the bag

The bag concentration times the chosen bag volume gives the total micrograms of drug to add. Convert to milligrams (divide by 1,000) for the size of stock you'll actually be drawing:

$$\text{total drug}_{\mu g} = \text{bag concentration}_{\mu g/mL} \times \text{bag volume}_{\text{mL}}$$
$$\text{total drug}_{mg} = \frac{\text{total drug}_{\mu g}}{1{,}000}$$

Step 3: volume of stock to draw

Total drug divided by the stock vial concentration gives the volume of stock to draw and add to the bag:

$$\text{stock volume}_{\text{mL}} = \frac{\text{total drug}_{mg}}{\text{stock}_{mg/mL}}$$

Worked through together: divide the total drug in the bag by the stock vial's mg/mL to get the mL of stock that contains that much drug. That is the volume to pull into the syringe and add to the bag.

Worked example with current inputs

Enter a patient weight to see the worked example.

Reference

Recommended dilutions

Target concentration Dilution When useful
16 µg/mL 1 vial (4 mg / 4 mL) into a 250 mL bag of 5% dextrose or 0.9% NaCl Standard preparation for patients ≥10 kg. Pump rate stays above 2 mL/hr at typical doses.
8 µg/mL 1 vial (4 mg / 4 mL) into a 500 mL bag of 5% dextrose or 5% dextrose with 0.9% NaCl Recommended for patients 4–10 kg. More dilute than the 250 mL preparation, so pump rate stays in the precision range for small/medium patients. Also used for prolonged infusions where bag-exchange frequency matters (sepsis, ICU).
4 µg/mL 1 vial (4 mg / 4 mL) into a 1 L bag of 5% dextrose or 5% dextrose with 0.9% NaCl Recommended for patients <4 kg or any patient at very low doses where the 8 µg/mL preparation would still drop pump rate below 2 mL/hr.

Standard preparation is the contents of one 4 mg vial (4 mL of 1 mg/mL stock) added to a single bag of carrier fluid. The resulting concentration depends on bag size: 250 mL gives 16 µg/mL, 500 mL gives 8 µg/mL, and 1 L gives 4 µg/mL. Most general practices use the 250 mL bag for typical surgical infusions. Commercial premixed bags (4, 8, and 16 mg in 250 mL) are also available and avoid the compounding step. Carrier fluid: for short anesthesia and surgical infusions (minutes to a few hours), either 5% dextrose or 0.9% NaCl is acceptable. For prolonged infusions in sepsis or ICU care, a dextrose-containing diluent is preferred because the mildly acidic pH slows oxidative degradation of the catecholamine. Discard any solution that has turned pink, brown, or developed a precipitate. Do not co-administer norepinephrine in a line containing sodium bicarbonate or other alkalinizing solutions, and do not mix it with iron-containing fluids or oxidizing agents. If you need to compound D5W from concentrated stock, see the Solution Preparation tool at /tools/d5w-prep.

Dilution helper — Norepinephrine CRI

Work out how many mL of stock drug and diluent to combine for any target concentration. Stock is pre-filled for Norepinephrine CRI; change it if you're using a different vial.

Suggestions from the reference table above
Draw up

Enter stock, target concentration, and final volume.