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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine that acts primarily as an alpha-adrenergic agonist, causing vasoconstriction, and to a lesser extent, a beta-1 adrenergic agonist, increasing heart rate and contractility. It is primarily used to increase blood pressure in hypotensive states.
## Primary Indications
* Management of severe hypotension and shock (e.g., septic shock, cardiogenic shock) unresponsive to adequate fluid resuscitation.
## Adult Dosing
* **Initiation:** Typically started at a low dose and titrated to achieve the desired blood pressure response. Common starting doses range from **2 mcg/min to 10 mcg/min** via continuous intravenous infusion.
* **Titration:** Increase dose by **2-10 mcg/min** every 5-15 minutes as needed.
* **Maximum Dose:** Doses up to **0.1 mcg/kg/min (or 10-30 mcg/min)** have been used, but higher doses are associated with increased risk of adverse events. Actual maximum dose can be protocol-dependent.
## Pediatric Dosing
* **Initiation:** **0.05 mcg/kg/min** via continuous intravenous infusion.
* **Titration:** Increase dose by **0.05-0.1 mcg/kg/min** every 5-15 minutes as needed.
* **Maximum Dose:** Generally **0.1 mcg/kg/min**, but higher doses up to **1 mcg/kg/min** may be used in refractory shock under expert guidance. Dosing is often guided by local pediatric resuscitation protocols.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment. However, use with caution as efficacy and clearance may be altered.
* **Hepatic Impairment:** No specific dose adjustment. However, use with caution as efficacy and clearance may be altered.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to absolute or relative hypovolemia (unless used as a temporizing measure prior to volume correction).
* Do not use during general anesthesia with cyclopropane or halogenated hydrocarbon anesthetics due to risk of severe hypertension and arrhythmias.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, chest pain, palpitations, peripheral ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Respiratory:** Dyspnea.
* **Other:** Reduced blood flow to vital organs (renal, splanchnic), decreased cardiac output at high doses.
## Key Drug Interactions
* **MAO Inhibitors & TCAs:** Potentiate hypertensive effects. Discontinue MAOIs at least 14 days before norepinephrine.
* **Beta-blockers:** May cause unopposed alpha-stimulation leading to severe hypertension.
* **Oxytocic Agents:** May cause severe sustained hypertension.
* **Ergot Alkaloids:** May enhance vasoconstrictive effects.
## Monitoring
* **Hemodynamics:** Continuous ECG, invasive blood pressure monitoring (arterial line preferred). Monitor heart rate, rhythm, and blood pressure closely.
* **Perfusion:** Assess peripheral circulation, urine output, mental status.
* **Infusion Site:** Regularly inspect for signs of extravasation.
## Clinical Pearls
* Norepinephrine is a potent vasoconstrictor and should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue infusion immediately and infiltrate the affected area with **phentolamine mesylate**.
* It should be used in conjunction with adequate volume resuscitation.
* Norepinephrine is light-sensitive; protect infusion bags from light.
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*This information is intended for healthcare professionals. Always consult the official prescribing information and relevant institutional protocols for the most up-to-date and complete details before prescribing or administering any medication.*
