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# Norepinephrine
## Overview
Norepinephrine is a potent alpha-1 adrenergic agonist and a weaker beta-1 adrenergic agonist. It causes peripheral vasoconstriction, increasing systemic vascular resistance and blood pressure. It also has a mild positive inotropic and chronotropic effect on the heart.
## Primary Indications
* Treatment of severe hypotension and shock (e.g., septic shock, cardiogenic shock).
## Adult Dosing
* **Initial dose:** 0.01 to 0.02 mcg/kg/min via continuous intravenous infusion.
* **Titration:** Increase dose by 0.01 to 0.02 mcg/kg/min every 2-5 minutes as needed to achieve target mean arterial pressure (MAP) of 65 mmHg or higher, or as dictated by local protocol.
* **Maximum dose:** Doses may range from 0.1 mcg/kg/min to 1.5 mcg/kg/min, or higher in refractory cases, per institutional guidelines.
## Pediatric Dosing
* **Initial dose:** 0.05 to 0.1 mcg/kg/min via continuous intravenous infusion.
* **Titration:** Increase dose as needed to maintain adequate blood pressure. Doses can range from 0.1 to 2 mcg/kg/min. Dosing is highly dependent on patient condition and local protocols.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but caution and close monitoring are advised.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but caution and close monitoring are advised.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during cyclopropane and halothane anesthesia (risk of severe hypertension and cardiac arrhythmias).
## Adverse Effects
* **Common:** Hypertension, bradycardia (reflex), peripheral ischemia, arrhythmias, headache, anxiety, decreased cardiac output.
* **Serious:** Extravasation leading to tissue necrosis (requires immediate discontinuation and local infiltration with phentolamine).
## Key Drug Interactions
* **Anesthetics (e.g., cyclopropane, halothane):** Increased risk of severe hypertension and cardiac arrhythmias.
* **MAO inhibitors and Tricyclic Antidepressants:** Potentiate the pressor response; administer with extreme caution and potentially reduced initial doses if co-administered.
* **Beta-adrenergic blockers:** May result in unopposed alpha-adrenergic stimulation, leading to severe hypertension.
* **Alpha-adrenergic blockers:** May antagonize the pressor effects.
* **Oxytocic agents:** May cause severe, sustained hypertension.
## Monitoring
* **Hemodynamic parameters:** Continuous ECG, arterial blood pressure (invasive preferred), heart rate.
* **Urine output:** To assess adequate perfusion.
* **Peripheral perfusion:** Assess skin color, temperature, and capillary refill.
* **Infusion site:** For signs of extravasation.
* **Electrolytes and acid-base status.**
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of extravasation.
* If extravasation occurs, stop the infusion immediately and infiltrate the affected area with phentolamine.
* Discontinue norepinephrine infusion gradually to avoid sudden hypotension.
* The goal of therapy is to restore adequate tissue perfusion, not just to achieve a specific blood pressure target.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication. Dosing and recommendations may vary.*
