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# Norepinephrine
## Overview
A potent endogenous catecholamine with primary alpha-1 adrenergic activity (vasoconstriction) and moderate beta-1 adrenergic activity (inotropy). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Hypotension or shock (distributive, cardiogenic).
* Cardiac arrest (rarely used as first-line).
## Adult Dosing
* **Shock:** Start infusion at 0.01–0.05 mcg/kg/min.
* **Titration:** Increase by 0.01–0.05 mcg/kg/min every 3–5 minutes based on mean arterial pressure (MAP) goals.
* **Typical Range:** 0.05–0.5 mcg/kg/min.
* **Max Dose:** No strict physiological maximum; doses >1 mcg/kg/min are considered high-dose and increase risk of organ ischemia.
## Pediatric Dosing
* **Shock:** Start at 0.05–0.1 mcg/kg/min.
* **Titration:** Increase to maintain age-appropriate blood pressure/perfusion.
* **Typical Range:** 0.05–1 mcg/kg/min.
* **Note:** Dosing is weight-based; refer to local PALS/PICU protocols for specific titration steps.
## Dose Adjustments
* **Renal/Hepatic:** No formal dose adjustments; prioritize hemodynamic stability.
* **Peripheral Administration:** Can be administered peripherally in a dilute concentration for a limited time in extreme emergencies, but central venous access is strongly preferred to prevent extravasation necrosis.
## Contraindications
* Hypersensitivity to norepinephrine or sulfites.
* Hypovolemia (unless corrected with volume resuscitation).
* Mesenteric or peripheral vascular thrombosis (relative contraindication).
## Adverse Effects
* **Cardiovascular:** Tachycardia, arrhythmias, hypertension, bradycardia (reflex).
* **End-Organ:** Peripheral or visceral ischemia (due to potent vasoconstriction).
* **Local:** Extravasation necrosis (treat with phentolamine infiltration if local ischemia occurs).
## Key Drug Interactions
* **MAO Inhibitors/TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-Blockers:** May lead to unopposed alpha-adrenergic stimulation (severe hypertension and reflex bradycardia).
* **Anesthetics (Halogenated hydrocarbons):** Increased risk of ventricular arrhythmias.
## Monitoring
* **Continuous:** ECG, invasive arterial blood pressure (preferred), heart rate, SpO2.
* **Perfusion:** MAP targets, urine output, serum lactate, mental status, skin temperature/capillary refill.
* **Site:** Hourly assessment of IV site for signs of extravasation.
## Clinical Pearls
* **Volume Status:** Norepinephrine is ineffective if the patient is severely hypovolemic; ensure adequate fluid resuscitation prior to or concurrent with initiation.
* **Titration:** Always taper dose slowly to avoid rebound hypotension.
* **Extravasation:** If extravasation occurs, stop the infusion immediately, leave the cannula in place to aspirate medication, and consider phentolamine (5–10 mg in 10 mL saline) infiltration.
* **Tachyphylaxis:** May occur with prolonged use; monitor for rising requirements.
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**Disclaimer:** This information is for educational purposes only. Always consult your facility's specific clinical guidelines, institutional protocols, and current prescribing information (package insert) before clinical use. Pediatric dosing should be double-checked by a second clinician due to the high risk of medication errors.
