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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and secondary beta-1 adrenergic agonist activity (inotropic effect). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Hypotension or shock (septic, cardiogenic, or distributive) refractory to fluid resuscitation.
* Hemodynamic support during resuscitation from cardiac arrest.
## Adult Dosing
* **Initial:** 0.01 to 0.05 mcg/kg/min (or 5–30 mcg/min) via continuous IV infusion.
* **Titration:** Titrate by 0.03–0.05 mcg/kg/min every 3–5 minutes to achieve target Mean Arterial Pressure (MAP), typically ≥ 65 mmHg.
* **Maintenance:** 0.01–3 mcg/kg/min.
* *Note:* Dosing is highly dependent on institutional protocols and the severity of hemodynamic instability.
## Pediatric Dosing
* **Continuous IV Infusion:** Start at 0.05–0.1 mcg/kg/min.
* **Titration:** Increase in increments of 0.05–0.1 mcg/kg/min as needed to maintain adequate perfusion.
* **Max:** Generally considered 1–2 mcg/kg/min in clinical practice, though higher doses are occasionally used in refractory pediatric shock under specialist supervision.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific adjustment required.
* **Weaning:** Patients should be titrated off gradually to prevent rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected hypovolemia (must address volume status concurrently).
## Adverse Effects
* **Extravasation:** Risk of local tissue necrosis and sloughing (treat with phentolamine if infiltration occurs).
* **Cardiovascular:** Tachyarrhythmias, bradycardia (reflex), limb ischemia, and mesenteric ischemia.
* **Neurological:** Headache, anxiety.
* **Respiratory:** Dyspnea.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-Blockers:** May decrease the efficacy of norepinephrine and increase the risk of hypertension via unopposed alpha-adrenergic stimulation.
* **General Anesthetics:** Use caution with halogenated hydrocarbons (e.g., cyclopropane, halothane) due to increased risk of ventricular arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous MAP monitoring via arterial line is strongly recommended.
* **Cardiac:** Continuous ECG for heart rate and rhythm monitoring.
* **Perfusion:** Assess urine output, serum lactate, and capillary refill time to evaluate end-organ perfusion.
* **Site:** Inspect IV site frequently for signs of infiltration.
## Clinical Pearls
* **Central Line Requirement:** Strictly recommended; extravasation through a peripheral line can cause severe tissue necrosis. If peripheral administration is necessary in an emergency, use a large vein, monitor closely, and convert to central access as soon as possible.
* **Concentration:** Norepinephrine is typically diluted in D5W or NS. Standard concentrations vary by institution; always verify current "drip" concentrations to prevent dosing errors.
* **Correction of Hypovolemia:** Norepinephrine is a "bridge" and does not replace the need for aggressive fluid resuscitation in hypovolemic or septic patients.
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*Disclaimer: This information is for educational purposes only. Always verify current prescribing information, institutional protocols, and safety guidelines before administering medications.*
