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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 receptors (inotropic effect). It is the first-line vasopressor for distributive shock.
## Primary Indications
* Severe hypotension
* Septic shock
* Cardiogenic shock (often as an adjunct)
## Adult Dosing
* **Initial Infusion:** 0.01 to 0.05 mcg/kg/min or 2–4 mcg/min.
* **Titration:** Titrate to achieve target MAP (typically ≥65 mmHg). Usual range is 0.05 to 0.5 mcg/kg/min.
* **Maximum:** No strict maximum; however, doses >1 mcg/kg/min indicate refractory shock and require re-evaluation.
* *Note: Always consult local institutional protocols for specific titration increments.*
## Pediatric Dosing
* **Initial Infusion:** 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate by 0.05 mcg/kg/min increments to achieve target perfusion pressure.
* **Maximum:** Typically 2 mcg/kg/min.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No formal dose adjustments; use with caution.
* **Discontinuation:** Always taper gradually to prevent rebound hemodynamic instability.
## Contraindications
* Hypersensitivity to norepinephrine or sulfite-containing products.
* Mesenteric or peripheral vascular thrombosis (unless life-saving).
## Adverse Effects
* **Common:** Hypertension, arrhythmias (tachycardia/bradycardia).
* **Severe:** Extravasation leading to tissue necrosis/gangrene, bradycardia (reflex), limb ischemia, and metabolic acidosis (due to decreased tissue perfusion at high doses).
## Key Drug Interactions
* **MAO Inhibitors/TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-blockers:** May result in unopposed alpha-adrenergic vasoconstriction and severe hypertension.
* **General Anesthetics (e.g., cyclopropane, halothane):** Increase sensitivity of the heart to catecholamines, increasing arrhythmia risk.
## Monitoring
* **Continuous ECG:** Monitor for arrhythmias.
* **Invasive Arterial Line:** Strongly recommended for precise titration in unstable patients.
* **Perfusion Markers:** MAP, lactate, capillary refill, and urine output.
* **Site Check:** Monitor IV/central line site frequently for signs of extravasation.
## Clinical Pearls
* **Central Access:** Norepinephrine is a vesicant; administration through a large-bore central venous catheter is preferred to prevent tissue sloughing.
* **Extravasation Management:** If extravasation occurs, discontinue infusion and infiltrate the site with phentolamine (5-10 mg in 10 mL saline) locally.
* **Compatibility:** Administer in D5W or D5NS; unstable in saline alone. Avoid mixing with alkaline solutions (e.g., sodium bicarbonate) as this will inactivate the drug.
* **Shock State:** Norepinephrine should not be initiated until intravascular volume status has been optimized (fluid resuscitation).
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*Disclaimer: This information is for educational purposes only. Clinical practice and institutional guidelines vary widely. Always verify current weight-based protocols and prescribing information through your local pharmacy or hospital formulary before administration.*
