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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and moderate beta-1 adrenergic agonist activity (inotropic effect). It is a first-line vasopressor for distributive shock.
## Primary Indications
* Hypotension associated with septic, cardiogenic, or neurogenic shock.
* Hemodynamic support during cardiac arrest.
## Adult Dosing
* **Initial Infusion:** 0.05 to 0.5 mcg/kg/min (or a fixed rate of 2–4 mcg/min).
* **Titration:** Titrate to maintain target Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Maximum Dose:** No formal maximum exists; however, doses >1 mcg/kg/min are associated with significant end-organ ischemia and refractory tachycardia. Doses exceeding 1–2 mcg/kg/min should prompt consideration for adding a secondary agent (e.g., vasopressin).
## Pediatric Dosing
* **Initial Infusion:** 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min every 5–15 minutes based on hemodynamic response.
* **Maximum Dose:** Typically up to 1–2 mcg/kg/min.
* *Note: Dosing often varies by institutional protocol; verify against local pediatric resuscitation guidelines.*
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific standard dose adjustments required; however, use with caution in patients with preexisting peripheral vascular disease or severe cardiac ischemia.
## Contraindications
* Hypersensitivity to norepinephrine or sulfite-containing products.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain perfusion).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (bradycardia or tachycardia), limb ischemia.
* **Local:** Extravasation causes tissue necrosis due to intense localized vasoconstriction.
* **Metabolic:** Increased serum lactate (due to tissue hypoperfusion or aerobic glycolysis).
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May produce severe, prolonged hypertension.
* **Beta-Blockers:** May lead to unopposed alpha-adrenergic stimulation, resulting in severe hypertension and reflex bradycardia.
* **Cyclopropane or Halogenated Hydrocarbon Anesthetics:** Increased risk of ventricular arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (preferably via arterial line).
* **Perfusion:** Monitor limb temperature, capillary refill, and urine output.
* **Access Site:** Check IV line frequently for patency and signs of extravasation. Use a central venous catheter whenever possible.
* **Labs:** Monitor serum lactate and pH to evaluate for perfusion status.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, discontinue infusion and infiltrate the site immediately with **phentolamine** (5–10 mg in 10 mL saline) within 12 hours.
* **Compatibility:** Must be infused via a dedicated line or a line compatible with all concurrently running infusions. Norepinephrine is sensitive to light; ensure the bag is protected if applicable.
* **Weaning:** Wean slowly to avoid rebound hypotension; consider weaning "off" vasopressin or other pressors before norepinephrine if hemodynamically stable.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice and institutional protocols vary widely. Always verify current prescribing information, package inserts, and local hospital guidelines before administering medication.
