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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 vasopressor of choice for vasodilatory shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Cardiac arrest (as an adjunct).
## Adult Dosing
* **Initial:** 0.05 to 0.5 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate to maintain target Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Emergency bolus (rare):** 1–4 mcg/min IV (protocol dependent).
* **Maximum:** No strict pharmacologic maximum; however, doses exceeding 1–2 mcg/kg/min are associated with significant end-organ ischemia and refractory tachycardia.
## Pediatric Dosing
* **Continuous Infusion:** 0.05 to 1 mcg/kg/min IV/IO.
* **Titration:** Titrate to clinical effect (e.g., target perfusion markers, MAP).
* *Note: Dosing is highly protocol-dependent; consult local institutional guidelines for pediatric intensive care unit (PICU) standards.*
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal adjustments required; however, use with caution due to systemic vasoconstriction affecting renal perfusion.
* **Shock State:** Dose is entirely dependent on hemodynamic response. If vasopressor requirement becomes refractory, consider adjunct therapy (e.g., vasopressin).
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected blood volume deficit (hypovolemic shock), unless used as a life-saving temporizing bridge during volume resuscitation.
## Adverse Effects
* **Ischemia:** Extravasation necrosis (skin/soft tissue), mesenteric or peripheral limb ischemia.
* **Cardiovascular:** Hypertension, bradycardia (reflex), tachyarrhythmias.
* **Metabolic:** Lactic acidosis (secondary to peripheral vasoconstriction/hypoperfusion).
## Key Drug Interactions
* **MAO Inhibitors or TCAs:** May cause severe, prolonged hypertension; minimize doses.
* **Beta-blockers:** May cause excessive peripheral vasoconstriction and reflex bradycardia due to unopposed alpha-adrenergic stimulation.
* **Halogenated Hydrocarbons (e.g., Anesthetics):** Increased risk of ventricular arrhythmias.
## Monitoring
* **Continuous:** Continuous ECG monitoring and intra-arterial blood pressure monitoring are strongly recommended.
* **Perfusion:** Monitor peripheral pulses, skin color, and urine output.
* **Extravasation:** Frequent assessment of IV site; administration via central venous catheter is preferred to prevent skin necrosis.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, infiltrate the site with **phentolamine mesylate** (5–10 mg in 10 mL saline) locally to block alpha-receptors and prevent tissue necrosis.
* **Tapering:** Wean slowly to avoid rebound hypotension once the underlying etiology of shock is addressed.
* **Compatibility:** Ensure accurate dilution (typically 4–8 mg in 250 mL D5W or NS). Incompatible with alkaline solutions (e.g., sodium bicarbonate).
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**Disclaimer:** This information is for educational purposes for healthcare professionals. Clinical practice, institutional protocols, and prescribing guidelines may vary. Always verify current prescribing information, package inserts, and local protocols before initiating administration.
