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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent that acts primarily on alpha-1 adrenergic receptors, causing vasoconstriction and increasing blood pressure. It also has some beta-1 adrenergic effects, increasing cardiac contractility.
## Primary Indications
* Treatment of hypotension (low blood pressure) in settings such as septic shock and other distributive shock states.
* Restoration of hemodynamic stability.
## Adult Dosing
* **Continuous Infusion:** Initiate at 2 to 10 mcg/min. Titrate dose to achieve target blood pressure (e.g., systolic blood pressure of 90-100 mmHg or mean arterial pressure [MAP] of 65-75 mmHg, depending on patient condition and institutional protocol).
* **Maximum Dose:** Doses may be increased as needed based on response, with some protocols allowing up to 30 mcg/min or higher in refractory shock.
## Pediatric Dosing
* **Continuous Infusion:** Initiate at 0.05 to 0.1 mcg/kg/min. Titrate to achieve target blood pressure and adequate perfusion.
* **Maximum Dose:** Doses may be increased as needed, with some protocols allowing up to 1-2 mcg/kg/min. Specific pediatric dosing should be guided by institutional protocols.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential due to potential accumulation or altered pharmacodynamics.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during general anesthesia with cyclopropane or halogenated hydrocarbons due to potential for severe hypertension and cardiac arrhythmias.
* Hypotension resulting from factors other than shock (e.g., hypovolemia) that should be corrected first.
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis, cardiac arrest.
* **Central Nervous System:** Headache, dizziness, anxiety, tremor.
* **Other:** Dilated pupils, sweating.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) & Tricyclic Antidepressants (TCAs):** Potentiate pressor response; may require significantly reduced norepinephrine doses.
* **Alpha-adrenergic Blockers (e.g., prazosin, terazosin):** May antagonize the pressor effects.
* **Beta-adrenergic Blockers:** May antagonize the cardiac effects and potentially enhance alpha-mediated vasoconstriction.
* **Ergot Alkaloids & Oxytocics:** May cause severe prolonged hypertension.
* **Anesthetics (e.g., halothane, cyclopropane):** Increased risk of cardiac arrhythmias.
## Monitoring
* Continuous electrocardiogram (ECG).
* Continuous blood pressure monitoring (arterial line preferred).
* Central venous pressure (CVP) or pulmonary artery catheter (PAC) if indicated.
* Urine output.
* Signs of peripheral perfusion (e.g., skin color, temperature, capillary refill).
* Infusion site for signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of peripheral extravasation and tissue necrosis.
* In the event of extravasation, discontinue the infusion immediately and infiltrate the affected area with phentolamine.
* The rate of infusion should be gradually decreased rather than stopped abruptly to avoid sudden hypotension.
* Norepinephrine is light-sensitive and should be protected from light during administration.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional guidelines for definitive patient care decisions.
