Posted in Pharmacology

Norepinephrine, brand name Levophed, is a medication used in the critical care setting to maintain adequate blood pressure. It is dosed in mcg/min and requires careful titration and monitoring. Using the Straight A Nursing DRRUGS framework, let’s go through the need-to-know information about this common and powerful medication. As always, these pharmacology lessons do not include everything there is to know about a medication and are not medical advice. 

D: DRUG CLASS

Norepinephrine is in the therapeutic class of vasopressors. Vasopressors exert their action on the vessel wall, causing it to constrict…think of it as “pressing down” and that may help you remember that the diameter of the vessel gets smaller. This leads to an increase in mean arterial pressure.

Norepinephrine works mainly as an alpha-agonist, but has some beta-agonist activity as well. 

R: REGULAR DOSE RANGE

Norepinephrine is dosed in mcg/min with standard starting doses ranging anywhere from 0.5 to 5mcg/minute. Facility protocol and/or the MD order will dictate the starting dose and titration intervals, and they must be followed very specifically. For example, the facility where I work typically starts norepinephrine at 1 mcg/minute with a titration of 1mcg every five minutes until the desired effect on blood pressure is reached. However, if the hypotension is severe, the MD may order a higher starting dose. Once the norepinephrine gets up to about 8 mcg/min, we start looking at adding a second vasopressor such as vasopressin. And, in really sick patients, the norepinephrine dose can get pretty high, with max doses at 30mcg/min. If you have a patient on norepinephrine at 30mcg/minute, they’re very, very, very sick.

In children, the dose ranges are much smaller, and are weight based at 0.1mcg/kg/min.

R: ROUTES

Norepinephrine is given as a continuous IV infusion, preferably through a central line. You may see low-dose norepinephrine given through a large peripheral IV, but this is only for time periods less than 24 hours and only if the patient does not need additional vasopressor support.

U: USES

Norepinephrine is used to increase mean arterial pressure (MAP) after the patient with severe hypotension and shock has received adequate fluid resuscitation. Let’s repeat that because it’s vital that you understand this: you do not give norepinephrine to patients in septic shock without first giving them adequate fluids. When a patient has sepsis and is hypotensive, we give a weight-based fluid bolus of 30ml/kg. If they remain hypotensive after fluid resuscitation, then we may look at starting a vasopressor such as norepinephrine.

G: GUIDELINES

  • Norepinephrine is not to be used in pregnancy as it decreases uterine blood flow
  • If the patient is taking an MAO inhibitor or tricyclic antidepressant, it can result in severe hypertension so be very careful
  • The patient receiving norepinephrine must be continuously monitored, with BP measurements every 2-3 minutes while titrating the medication, then every 5-15 minutes when the infusion is steady (depending on facility protocol). An arterial line makes this much easier as it provides real-time data and is more comfortable for the patient.
  • Monitor urine output as a way to measure adequate organ perfusion.
  • Keep a very close eye on that IV site as extravasation can cause tissue necrosis.
  • Consider using a flush line as you wean the patient off the norepinephrine. Many times you’ll get down to very low doses of medication, possibly turning it off for a bit, then on again. Having a flush line running at a slow rate, prevents you from having to “hard-flush” the line when turning it off. While a peripheral IV may not have much medication sitting in it, a PICC line can have about 2ml, which equates to 8mcg of norepinephrine. In a perfect world, you’d disconnect the norepinephrine, withdraw the medication sitting in the line and discard it, followed by a hard flush with 10-20 ml normal saline. Unfortunately, you can’t always count on being able to draw from a PICC line, so running in a slow infusion of normal saline will drip the remaining 2 ml of medication in slowly so as to not adversely affect blood pressure. As always, please refer to facility protocol regarding flushes, vasoactive medications and the use of TKO or flush lines.
  • Vasopressors are high-alert medications, so it is always advised that you have a second RN check your dose before starting the infusion.

S: SIDE EFFECTS

The most serious adverse effects of norepinephrine have to do with its vasoconstrictive activity. At high and prolonged doses it can cause tissue ischemia leading to necrosis of peripheral tissues such as fingers and toes. It can also cause phlebitis at the IV site and renal failure. Other side effects include: 

  • Headache, anxiety, restlessness, tremor
  • Hyperglycemia
  • Metabolic acidosis
  • Dyspnea
  • Chest pain, dysrhythmias, bradycardia

How about a little practice with dosage calculations?

Practice Question 1: 

Your patient is receiving 8mcg/min of norepinephrine which comes in a 250 ml bag containing 8 mg of medication. How many ml/hour should the infusion pump be set for? 

Practice Question 2: 

Your patient is receiving an infusion of norepinephrine at 22.5 ml/h. How many mcg are they receiving per minute?

Practice Question 3:

The MD has ordered for your patient to receive an infusion of norepinephrine starting at 1mcg/min and titrated by 1mcg/min every five minutes to maintain a MAP of 65. The infusion was started at 1905 and it is now 1920. The patient’s MAP measurements have all been below 65, so the medication has been increased as ordered every five minutes. How many ml/hour is the patient currently receiving?

Practice Question 4:

Your patient is very unstable and requiring high doses of norepinephrine. You want to make sure the 250ml bag containing 8mg of medication does not run out while you take your other patient to MRI. The patient is receiving 30mcg/min of norepinephrine, and there is currently 100ml remaining in your bag. It is now 1230 and you expect to be gone for two hours. How many ml per hour is the patient receiving, and do you expect this bag to complete while you are gone?

Answers below, no peeking until you’ve tried!

 

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References

Deglin, J. H., & Vallerand, A. H. (2007). Davis’s drug guide for nurses (11th ed.). F. A. Davis Company.

McCance, K. L., & Huether, S. E. (2019). Pathophysiology: The biologic basis for disease in adults and children(Eighth). Elsevier.

Urden, L. D., Stacy, K. M., & Lough, M. E. (2010). Critical Care Nursing Secrets: Diagnosis and Management (Sixth). Mosby Elsevier.

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Answers below! Keep scrolling!

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Answers to practice questions

Question 1: 15ml/hr

Question 2: 12mcg/min

Question 3: 7.5ml/hr

Question 4: 56.25ml/hr; Yes, this bag will complete within the two hour window you expect to be off the unit. Make sure this information is conveyed to the nurse who will be assuming care while  you take your other patient to MRI.

How’d you do? If you got stuck, had trouble figuring out where to start, weren’t sure what the question was asking or couldn’t get your conversions to cancel out…then you will LOVE the confidence and skills you’ll get from my Dosage Calculations Bootcamp. I hope to see you there!

 

Listen to this topic in episode 139 of the Straight A Nursing podcast here or wherever you get your podcast fix.

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