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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotrope that acts primarily on alpha-adrenergic receptors, causing vasoconstriction and increasing systemic vascular resistance. It also has some beta-1 adrenergic activity, which can increase heart rate and contractility.
## Primary Indications
* Severe hypotension and shock (e.g., septic shock, cardiogenic shock, anaphylactic shock) refractory to adequate fluid resuscitation.
* Cardiac arrest (used in ACLS algorithms).
## Adult Dosing
* **Hypotension/Shock:** Initiate infusion at 0.01 to 0.02 mcg/kg/min. Titrate to achieve target mean arterial pressure (MAP) of 65 mmHg or higher. Typical maintenance doses range from 0.01 to 0.3 mcg/kg/min. Maximum dose is generally considered 1-2 mcg/kg/min, but higher doses may be used in refractory shock under expert guidance.
* **Cardiac Arrest:** As per ACLS guidelines, 1 mg IV/IO every 3-5 minutes.
## Pediatric Dosing
* **Hypotension/Shock:** Initiate infusion at 0.05 to 0.1 mcg/kg/min. Titrate to achieve target MAP (systolic BP > gestational age + 5 mmHg for neonates, or 5th percentile systolic BP for older children). Typical maintenance doses range from 0.05 to 0.2 mcg/kg/min. Maximum dose is generally considered 1-2 mcg/kg/min, but higher doses may be used in refractory shock under expert guidance.
* **Cardiac Arrest:** As per PALS guidelines, 0.01 mg/kg IV/IO (10 mcg/kg), maximum 1 mg. Repeat every 3-5 minutes.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, as the drug is primarily metabolized and has rapid effects. However, close monitoring is essential in patients with pre-existing conditions.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to absolute hypovolemia without adequate fluid replacement.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia, arrhythmias, peripheral ischemia, myocardial infarction, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Metabolic:** Hyperglycemia.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Potentiate the pressor effects of norepinephrine, potentially leading to severe hypertension. Discontinue MAOIs at least 14 days prior to norepinephrine use.
* **Anesthetic Agents (e.g., Halogenated anesthetics):** May increase myocardial irritability and risk of arrhythmias.
* **Beta-blockers:** Can unmask unopposed alpha-adrenergic receptor stimulation, leading to severe hypertension.
* **Alpha-blockers:** Can reduce the pressor effect of norepinephrine.
## Monitoring
* Continuous ECG monitoring for arrhythmias.
* Frequent blood pressure monitoring (arterial line preferred for continuous infusions).
* Monitor urine output.
* Assess peripheral circulation (e.g., skin temperature, color, capillary refill).
* Monitor for signs of extravasation.
* Monitor serum glucose levels.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter whenever possible to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, stop the infusion and infiltrate the affected area with phentolamine.
* Norepinephrine is light-sensitive; protect infusions from light.
* Titrate infusion rates to achieve desired hemodynamic goals, not based on absolute dose.
* Ensure adequate fluid resuscitation before and during norepinephrine administration.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines for complete details and to verify dosing and safety information before administering any medication.*
