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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 adrenergic receptors (inotropic effect). It is the first-line vasopressor for distributive shock (e.g., septic shock) due to its efficacy in maintaining mean arterial pressure (MAP).
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Adjunctive therapy in cardiac arrest (if protocol dictates).
## Adult Dosing
* **Initial Infusion:** 0.05 to 0.1 mcg/kg/min or 2 to 4 mcg/min (fixed rate).
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min every 1–2 minutes to achieve target MAP (typically ≥65 mmHg).
* **Maximum Dose:** No formal maximum; doses >1–3 mcg/kg/min may be required in refractory cases, though benefit should be weighed against risk of end-organ ischemia.
## Pediatric Dosing
* **Initial Infusion:** 0.05 to 0.1 mcg/kg/min.
* **Titration:** Increase in increments of 0.05 mcg/kg/min to achieve target perfusion goals.
* **Maximum Dose:** Typically up to 1–2 mcg/kg/min. Clinical judgment and local institutional protocols must guide titration in pediatric populations.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No specific adjustment required. Use caution and lower starting doses in patients with baseline high risk for ischemia.
* **Titration:** Always taper infusion gradually rather than abrupt discontinuation to avoid rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine or sulfites.
* Hypotension due to uncorrected hypovolemia (volume resuscitation must precede or accompany vasopressor initiation).
* Mesenteric or peripheral vascular thrombosis (due to severe vasoconstriction potential).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (tachycardia or bradycardia reflex), myocardial ischemia.
* **Local:** Extravasation can lead to skin necrosis and sloughing.
* **Systemic:** Decreased renal/splanchnic blood flow, metabolic acidosis (lactic acidosis).
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May enhance the pressor response; monitor for severe hypertension.
* **Beta-blockers:** May result in unopposed alpha-adrenergic vasoconstriction (severe hypertension and reflex bradycardia).
* **Cyclopropane/Halogenated Hydrocarbons:** Increased risk of ventricular arrhythmias.
## Monitoring
* **Continuous:** Blood pressure (preferably via arterial line), heart rate, and ECG (rhythm).
* **Perfusion:** MAP, urine output, mental status, serum lactate, and capillary refill.
* **Site:** Strict assessment for extravasation at infusion site. Treat extravasation immediately with phentolamine (alpha-blocker) if protocol dictates.
## Clinical Pearls
* **Peripheral Administration:** Safe for short-term use in a large-bore, proximal vein (avoid distal hand/wrist veins) until central access is obtained, provided the concentration is sufficiently diluted; monitor for extravasation rigorously.
* **Septic Shock:** Surviving Sepsis Campaign guidelines recommend starting norepinephrine early in the management of septic shock.
* **Titration:** Norepinephrine is a high-alert medication; use smart pumps with dose-error reduction systems.
* **Protocol:** Always verify specific dosing requirements against your institution's approved clinical protocols.
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*Disclaimer: This information is for educational purposes only and does not supersede local institutional protocols. Verify all dosages and contraindications with the most current clinical resources and official prescribing information before administration.*
