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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and moderate beta-1 adrenergic agonist activity (inotropic effect). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Acute hypotensive states (e.g., septic, cardiogenic, or distributive shock).
* Adjunct in the treatment of cardiac arrest (though epinephrine remains first-line).
## Adult Dosing
* **Initial dose:** 0.01–0.05 mcg/kg/min or 2–4 mcg/min IV infusion.
* **Titration:** Increase by 0.05–0.5 mcg/kg/min or 2–4 mcg/min every 3–5 minutes until the desired hemodynamics (typically MAP >65 mmHg) are achieved.
* **Maintenance:** 0.01–3 mcg/kg/min.
* *Note:* Dosing is highly dependent on institutional protocols and clinical status; always titrate to the minimum effective dose.
## Pediatric Dosing
* **Shock/Hypotension:** 0.05–0.3 mcg/kg/min by continuous IV infusion.
* **Titration:** May increase by 0.05 mcg/kg/min every 5–10 minutes.
* Maximum doses should be guided by PALS or local institutional critical care guidelines.
## Dose Adjustments
* **Renal/Hepatic:** No specific standard dose adjustments, as activity is primarily determined by receptor-mediated hemodynamic response.
* **Tapering:** Must be tapered slowly to avoid precipitous hemodynamic collapse.
## Contraindications
* Hypersensitivity to norepinephrine or sulfites.
* Hypotension due to uncorrected blood volume deficit (except as a temporary emergency measure).
* Mesenteric or peripheral vascular thrombosis (relative contraindication).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, myocardial ischemia.
* **Local:** Extravasation can lead to tissue necrosis/sloughing.
* **Respiratory:** Dyspnea.
* **Other:** Anxiety, headache, limb ischemia.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May cause severe, prolonged hypertension due to increased catecholamine sensitivity.
* **Alpha/Beta Blockers:** May antagonize the effects of norepinephrine.
* **Inhalation Anesthetics:** May sensitize the myocardium to the arrhythmogenic effects of catecholamines (e.g., halothane, cyclopropane).
## Monitoring
* **Continuous arterial pressure monitoring:** Recommended for titration and accuracy.
* **Heart Rate/ECG:** Continuous monitoring for arrhythmias.
* **Peripheral perfusion:** Assess site of infusion frequently for signs of extravasation (pallor, coolness).
* **Renal output:** Monitor urine output as a surrogate for end-organ perfusion.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately and infiltrate the area with phentolamine (5–10 mg in 10 mL saline) as soon as possible.
* **Administration:** Must be administered via a central line for long-term use to minimize the risk of limb ischemia from extravasation, though it can be used briefly peripherally in large veins in emergencies.
* **Compatibility:** Must be diluted in D5W or D5W/NS. Do not use plain Normal Saline for long-term stability in some preparations; refer to institutional product monographs.
* **Effectiveness:** In refractory shock, norepinephrine is often titrated until MAP goals are met; failure to respond usually warrants the addition of vasopressin.
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*Disclaimer: This information is for educational purposes only. Always consult your institution's specific clinical protocols and the official manufacturer's prescribing information before ordering or administering medications.*
