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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) with moderate beta-1 adrenergic effects (inotropic support). It is the first-line vasopressor for septic and vasodilatory shock.
## Primary Indications
* First-line treatment for septic shock.
* Hemodynamically significant hypotension (refractory to fluid resuscitation).
* Cardiac arrest (rare, usually reserved for refractory cases per advanced protocols).
## Adult Dosing
* **Initial Infusion:** 0.01 to 0.03 mcg/kg/min (or 2–4 mcg/min fixed dose).
* **Titration:** Titrate every 3–5 minutes by 0.05–0.2 mcg/kg/min to achieve target Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Maintenance:** Generally 0.01–3 mcg/kg/min.
* **Maximum:** No defined absolute maximum dose; however, doses >1–2 mcg/kg/min are associated with significant mortality and severe ischemia.
## Pediatric Dosing
* **Continuous Infusion:** Start at 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate as needed to maintain age-appropriate blood pressure.
* *Note:* Pediatric dosing is highly protocol-dependent; consult institutional guidelines for specific neonatal or pediatric intensive care unit (PICU) titration parameters.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific dosage adjustments established, but use caution due to potential for vasoconstriction-induced ischemia.
* **Geriatrics:** Start at the lower end of the dosing range due to increased sensitivity to adrenergic stimulation.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected hypovolemia (must restore volume status first).
* Mesenteric or peripheral vascular thrombosis (risk of worsening ischemia).
## Adverse Effects
* **Cardiovascular:** Tachycardia, arrhythmias (atrial/ventricular), hypertension, myocardial ischemia.
* **Local:** Extravasation can cause severe tissue necrosis and sloughing.
* **Systemic:** Peripheral/visceral ischemia, digital gangrene, metabolic acidosis.
## Key Drug Interactions
* **MAOIs/Tricyclic Antidepressants:** May cause severe, prolonged hypertension.
* **Beta-blockers:** May result in unopposed alpha-adrenergic activity, causing sudden, severe hypertension and bradycardia.
* **Halogenated Hydrocarbons (e.g., volatile anesthetics):** May sensitize the myocardium to arrhythmogenic effects.
## Monitoring
* **Hemodynamics:** Continuous invasive arterial blood pressure monitoring is strongly recommended.
* **Perfusion:** Assess distal limb perfusion, urine output (renal perfusion), and serum lactate levels.
* **Access Site:** Check for signs of extravasation frequently. Infusion via a large peripheral vein (for short duration) or central venous catheter is preferred.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, discontinue infusion immediately, elevate the limb, and consider local infiltration of phentolamine (alpha-adrenergic antagonist).
* **First-line:** Norepinephrine is currently preferred over dopamine for septic shock due to lower risk of arrhythmias.
* **Weaning:** Taper slowly; abrupt discontinuation can cause rapid hemodynamic collapse.
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*Disclaimer: This information is for educational purposes and does not replace professional clinical judgment. Always verify current prescribing information, institutional protocols, and drug compatibility datasheets before administration.*
