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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily as an alpha-1 adrenergic agonist (vasoconstriction) with moderate beta-1 adrenergic activity (inotropic effect). It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock, anaphylaxis post-fluid resuscitation).
* Cardiac arrest (less common than epinephrine).
## Adult Dosing
* **Initial Infusion:** 0.01–0.05 mcg/kg/min (or 2–5 mcg/min fixed dose).
* **Titration:** Titrate by 0.01–0.05 mcg/kg/min every 3–5 minutes based on mean arterial pressure (MAP) goals (typically MAP ≥65 mmHg).
* **Maintenance Range:** 0.01–3 mcg/kg/min.
* **Maximum:** No absolute maximum; limited by patient tolerance and secondary organ ischemia.
## Pediatric Dosing
* **Continuous Infusion:** Start at 0.05–0.1 mcg/kg/min.
* **Titration:** Titrate by 0.05 mcg/kg/min to achieve goal systolic blood pressure or perfusion markers.
* **Maintenance Range:** 0.05–2 mcg/kg/min.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific adjustment required; however, monitor closely for tissue hypoperfusion.
* **Geriatric:** Start at the lower end of the dosing range due to increased sensitivity to pressors.
## Contraindications
* Hypotension due to uncorrected hypovolemia (must restore volume before/concomitantly with initiation).
* Hypersensitivity to sulfites.
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (tachycardia/bradycardia), myocardial ischemia.
* **Local:** Extravasation can lead to severe tissue necrosis and sloughing (if leakage occurs, infiltrate area with phentolamine).
* **Metabolic:** Lactic acidosis (secondary to intense vasoconstriction).
## Key Drug Interactions
* **MAO Inhibitors/Antidepressants:** May cause severe, prolonged hypertension.
* **Beta-Blockers:** May exacerbate vasoconstriction by blocking beta-2 mediated vasodilation, resulting in unopposed alpha-adrenergic activity.
* **Cyclopropane/Halogenated Hydrocarbon Anesthetics:** Increase cardiac sensitivity to catecholamines, increasing arrhythmia risk.
## Monitoring
* **Continuous ECG:** Monitor for rate or rhythm changes.
* **Blood Pressure:** Arterial line preferred for titration.
* **Perfusion Markers:** Monitor urine output, capillary refill, skin color, and lactate levels.
* **Site Checks:** Assess IV infusion site hourly for signs of extravasation.
## Clinical Pearls
* **Central Access:** Administer through a large central vein whenever possible to reduce extravasation risk. Peripheral administration is acceptable via a small-gauge (distal) catheter for short durations at lower concentrations, though carries inherent risks.
* **Weight-Based Dosing:** Standardizing to mcg/kg/min is preferred in many ICUs to prevent dosing errors, though "fixed" mcg/min ranges are widely used in adult medicine. *Always consult local hospital protocol for standardized concentration and dosing preferences.*
* **Shock State:** Norepinephrine should not be initiated until absolute hypovolemia is addressed via fluid resuscitation, if indicated.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice varies by institution. Always verify current prescribing information, local hospital protocols, and patient-specific factors before administration.
