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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-adrenergic activity (vasoconstriction) and moderate beta-1 adrenergic activity (inotropic effect). It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states.
* Septic shock (first-line).
* Cardiogenic shock (often used with dobutamine).
## Adult Dosing
* **Initial dose:** 0.05–0.1 mcg/kg/min or 2–4 mcg/min continuous IV infusion.
* **Titration:** Titrate to goal Mean Arterial Pressure (MAP) (typically 65 mmHg). Usual practice involves increasing by 0.05–0.1 mcg/kg/min every 3–5 minutes.
* **Maximum:** No absolute maximum dose; however, doses >1 mcg/kg/min are associated with significant toxicity and refractory shock. Local institutional protocols dictate maximum infusion rates.
## Pediatric Dosing
* **Initial dose:** 0.05–0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.05 mcg/kg/min every 5 minutes to achieve target blood pressure.
* **Maximum:** Typically 1–2 mcg/kg/min. Pediatric dosing should strictly follow institutional specialized protocols (e.g., PALS).
## Dose Adjustments
* **Renal/Hepatic:** No specific dosing adjustments provided by manufacturer, but monitor closely as clearance may be altered in organ failure.
* **Elderly:** Use caution; lower starting doses may be appropriate due to increased sensitivity and potential for cardiac arrhythmias.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to uncorrected blood volume deficit (must replace volume before or concurrently with vasopressor therapy).
* Mesenteric or peripheral vascular thrombosis.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, myocardial ischemia.
* **Local:** Extravasation can lead to tissue necrosis/sloughing.
* **Systemic:** Anxiety, headache, dyspnea, lactic acidosis (at high doses).
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May result in severe, prolonged hypertension.
* **Beta-blockers:** May lead to unopposed alpha-adrenergic vasoconstriction and severe hypertension.
* **Cyclopropane/Halogenated Hydrocarbon Anesthetics:** Increased risk of ventricular arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous intra-arterial blood pressure monitoring preferred.
* **Perfusion:** Monitor urine output, serum lactate, and distal extremity perfusion.
* **Site:** Assess IV site frequently for signs of extravasation.
* **E-cardio:** Continuous cardiac monitoring for arrhythmia.
## Clinical Pearls
* **Administration:** Must be administered via central venous access to prevent skin necrosis from extravasation. If extravasation occurs, consider local injection of phentolamine.
* **Compatibility:** Administer through a dedicated line if possible; norepinephrine is highly potent and incompatible with many drugs (e.g., sodium bicarbonate, alkaline solutions).
* **Weaning:** Wean slowly to avoid rebound hypotension.
* **Volume Status:** Norepinephrine is ineffective in hypovolemic patients until adequate fluid resuscitation is initiated.
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*Educational Disclaimer: This information is for educational purposes only. Clinical practice varies by institution. Always verify current dosing guidelines, compatibility, and safety protocols with your local formulary and clinical pharmacists before administration.*
