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# Norepinephrine
## Overview
Norepinephrine is a potent endogenous catecholamine and sympathomimetic amine that acts as a neurotransmitter and hormone. It primarily stimulates alpha-1 adrenergic receptors, causing vasoconstriction, and also has beta-1 adrenergic effects, increasing heart rate and contractility.
## Primary Indications
* Management of severe hypotension and shock, particularly in sepsis and cardiogenic shock.
* Restoration and maintenance of blood pressure.
## Adult Dosing
* **Intravenous infusion:** Typically initiated at 0.01 to 0.1 mcg/kg/min and titrated to achieve target blood pressure (e.g., mean arterial pressure [MAP] $\ge$ 65 mmHg).
* **Maximum dose:** Doses can be escalated as needed, with infusions up to 1 mcg/kg/min or higher sometimes required in severe shock. Specific maximums are often guided by clinical response and local protocols.
## Pediatric Dosing
* **Intravenous infusion:** Recommended starting dose is 0.05 to 0.1 mcg/kg/min, titrated to achieve target MAP.
* **Maximum dose:** Titrate as needed, often up to 1 mcg/kg/min. Higher doses may be used under specialist guidance. Local protocols are critical for pediatric dosing.
## Dose Adjustments
* No specific dose adjustments are routinely recommended for hepatic or renal impairment, but close monitoring is essential as these conditions can alter drug metabolism and excretion.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to relative hypovolemia (requires volume resuscitation prior to norepinephrine administration).
* Use with volatile anesthetic agents that sensitize the myocardium to catecholamines.
## Adverse Effects
* **Common:** Hypertension, bradycardia (reflex), peripheral ischemia, tissue necrosis (if extravasation occurs), anxiety, headache, dizziness, palpitations, arrhythmias.
* **Less Common:** Decreased cardiac output (at higher doses due to excessive vasoconstriction), respiratory distress.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiate hypertensive crisis. Avoid concurrent use or use with extreme caution and reduced norepinephrine doses.
* **Tricyclic Antidepressants (TCAs):** Potentiate hypertensive effects.
* **Beta-adrenergic Blockers:** Can unopposed alpha-adrenergic stimulation, leading to severe hypertension.
* **Alpha-adrenergic Blockers:** Can reduce the pressor effects of norepinephrine.
* **Ergot Alkaloids:** Can cause severe hypertension.
* **General Anesthetics:** May increase myocardial irritability and risk of arrhythmias.
## Monitoring
* **Hemodynamic:** Continuous arterial blood pressure monitoring (MAP), heart rate, cardiac rhythm.
* **Circulatory Status:** Monitor peripheral perfusion, skin temperature, color, and capillary refill.
* **Infusion Site:** Regularly assess for signs of extravasation (pain, swelling, skin discoloration).
* **Fluid Status:** Assess volume status and response to fluid resuscitation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately and administer an alpha-adrenergic blocking agent (e.g., phentolamine) infiltrated into the affected area.
* Titration should aim for the lowest effective dose to maintain adequate tissue perfusion and organ function, not just a specific MAP target in all patients.
* Consider underlying causes of hypotension (e.g., hypovolemia, cardiac dysfunction) and address them concurrently.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete and up-to-date details before making any therapeutic decisions.*
