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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent that acts primarily on alpha-adrenergic receptors, causing vasoconstriction and increased systemic vascular resistance. It also has some beta-1 adrenergic effects, increasing heart rate and contractility.
## Primary Indications
* Severe hypotension and shock, particularly distributive shock (e.g., septic shock, neurogenic shock).
* To maintain adequate blood pressure during septic shock and other forms of shock when fluid resuscitation alone is insufficient.
## Adult Dosing
* **Initial Dose:** 2-4 mcg/min (or 0.01-0.02 mcg/kg/min) IV infusion.
* **Titration:** Titrate infusion rate upward based on patient's hemodynamic response (e.g., mean arterial pressure [MAP] goal, typically $\geq$ 65 mmHg). Doses may range from 1-30 mcg/min (or 0.01-0.3 mcg/kg/min).
* **Maximum Dose:** Doses higher than 30 mcg/min may be used in refractory shock, but carry increased risk of adverse effects. Local protocols should be followed.
## Pediatric Dosing
* **Initial Dose:** 0.05-0.1 mcg/kg/min IV infusion.
* **Titration:** Titrate to desired hemodynamic effect, typically to achieve MAP $\geq$ age in years + 2 mmHg, up to a maximum of 70 mmHg. Doses may range from 0.05-2 mcg/kg/min.
* **Maximum Dose:** Local protocols should be followed; higher doses may be used with caution.
## Dose Adjustments
No specific dose adjustments for renal or hepatic impairment are established due to the critical nature of its use and rapid titration. However, continuous reassessment of patient status is crucial.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use as the sole agent to manage hypotension due to hypovolemia (must correct hypovolemia first).
* Patients with severe peripheral vascular disease or mesenteric vascular occlusion may be at increased risk of ischemic complications.
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, myocardial ischemia, peripheral ischemia, tissue necrosis (if extravasation occurs).
* **Other:** Headache, anxiety, tremors, dyspnea, decreased urine output.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Potentiate pressor effects, requiring significant dose reduction and careful titration. Avoid use if possible.
* **Alpha and Beta Blockers:** May antagonize or potentiate effects depending on the specific agent.
* **General Anesthetics:** May increase myocardial irritability and risk of arrhythmias.
## Monitoring
* Continuous electrocardiogram (ECG).
* Continuous blood pressure monitoring (arterial line preferred).
* Central venous pressure (CVP) and/or pulmonary artery catheter (PAC) readings if available.
* Urine output.
* Peripheral perfusion (e.g., skin temperature, color, capillary refill).
* Mental status.
## Clinical Pearls
* Always administer via a central venous catheter to reduce the risk of extravasation and tissue necrosis.
* Have phentolamine readily available for extravasation management.
* Titrate to the lowest effective dose to achieve hemodynamic goals.
* Monitor closely for signs of peripheral ischemia, especially in digits, nose, and ears.
* Norepinephrine is light-sensitive; protect infusions from light.
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*This information is intended for clinical professionals. Always consult the official prescribing information and local protocols for the most current and complete guidelines.*
