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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic catecholamine that acts primarily as an alpha-1 adrenergic agonist (vasoconstriction) and, to a lesser extent, a beta-1 adrenergic agonist (positive inotropy). It is the first-line vasopressor for septic shock.
## Primary Indications
* Hypotension refractory to fluid resuscitation.
* Septic shock.
* Distributive or cardiogenic shock.
## Adult Dosing
* **Initial Infusion:** 0.01–0.05 mcg/kg/min or 2–4 mcg/min (base).
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min (or 2–4 mcg/min) every 3–5 minutes to achieve target mean arterial pressure (MAP), typically 65 mmHg.
* **Maintenance:** Usual range is 0.01–3 mcg/kg/min.
* **Note:** Dosing varies significantly by local institutional protocols. Always verify concentrations (e.g., 4 mg/250 mL vs. 16 mg/250 mL).
## Pediatric Dosing
* **Initial Infusion:** 0.05–0.1 mcg/kg/min.
* **Titration:** Titrate to effect; common maximums are 1–2 mcg/kg/min.
* **Note:** Administration should ideally occur via a central line to prevent peripheral tissue complications.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No standard dose reduction required. Monitor for efficacy and toxicity.
* **Elderly:** Use lowest effective dose; monitor closely for arrhythmias and myocardial ischemia.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Profound hypotension primarily due to hypovolemia (must be corrected with fluids prior to/concurrently with initiation).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), tachycardia, cardiac arrhythmias, myocardial ischemia.
* **Local:** Extravasation leading to tissue necrosis and sloughing.
* **Systemic:** Anxiety, dyspnea, hyperglycemia.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-Blockers:** May lead to excessive alpha-mediated vasoconstriction and reflex bradycardia.
* **Halogenated Hydrocarbons (e.g., volatile anesthetics):** May sensitize the myocardium to catecholamines, increasing arrhythmia risk.
## Monitoring
* **Hemodynamics:** Continuous MAP monitoring (via arterial line preferred).
* **Cardiac:** Continuous ECG for heart rate and rhythm.
* **Perfusion:** Urine output, extremity color/temperature, and serum lactate levels.
* **Site:** Strict serial inspection of IV site for signs of extravasation.
## Clinical Pearls
* **Extravasation Management:** If infiltration occurs, stop infusion immediately. Consider local phentolamine (alpha-blocker) infiltration to prevent tissue necrosis.
* **Peripheral Administration:** Can be used peripherally for short durations in dilute concentrations through a large vein (ideally above the wrist), though central access is preferred for prolonged therapy.
* **Stability:** Ensure correct dilution; norepinephrine is sensitive to light.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice varies by institution. Always verify current prescribing information, institutional protocols, and patient-specific factors before administration.
