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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine that acts primarily as an alpha-adrenergic agonist, causing vasoconstriction. It also has some beta-1 adrenergic agonist activity, increasing heart rate and contractility. It is a vasopressor used to treat severe hypotension.
## Primary Indications
* Treatment of severe hypotension, particularly in shock states (e.g., septic shock, cardiogenic shock) to restore and maintain blood pressure.
## Adult Dosing
* **Starting Dose:** 0.01 to 0.02 mcg/kg/min intravenously.
* **Titration:** Gradually increase the dose by 0.01 to 0.02 mcg/kg/min every 2 to 5 minutes until the desired blood pressure is achieved.
* **Maximum Dose:** Typically up to 0.3 mcg/kg/min, though higher doses may be used in refractory hypotension under close medical supervision.
* **Note:** Specific titration rates and target blood pressure goals are often dictated by institutional protocols and patient-specific clinical status.
## Pediatric Dosing
* **Starting Dose:** 0.05 mcg/kg/min intravenously.
* **Titration:** Increase by 0.05 to 0.2 mcg/kg/min increments every 5 to 10 minutes as needed.
* **Maximum Dose:** Typically up to 1 mcg/kg/min, though higher doses may be used in refractory hypotension under close medical supervision.
* **Note:** Pediatric dosing and titration guidelines can vary significantly; confirm with current institutional protocols or pediatric critical care resources.
## Dose Adjustments
* No specific dose adjustments are typically required for renal or hepatic impairment, as norepinephrine is metabolized rapidly. However, close monitoring of cardiovascular response is essential in all patients.
## Contraindications
* Hypersensitivity to norepinephrine.
* Concurrent use with cyclopropane or halogenated hydrocarbon anesthetics (risk of severe arrhythmias).
* Avoid use in patients with mesenteric or peripheral vascular thrombosis, as it may increase ischemia.
## Adverse Effects
* **Common:** Hypertension, reflex bradycardia, peripheral ischemia, skin necrosis (especially with extravasation), anxiety, headache, dizziness, tremors, palpitations.
* **Serious:** Arrhythmias, severe hypertension, pulmonary edema, limb ischemia, gangrene.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Can potentiate the pressor effect of norepinephrine, leading to severe hypertension. Discontinue MAOIs at least 2 weeks prior to starting norepinephrine.
* **Beta-adrenergic Blockers:** May blunt the beta-1 effects of norepinephrine, potentially leading to unopposed alpha-stimulation and severe peripheral vasoconstriction.
* **Alpha-adrenergic Blockers:** May antagonize the pressor effect of norepinephrine.
* **Ergot Alkaloids:** May potentiate the vasoconstricting effects.
* **Oxytocics:** May cause severe hypertension.
## Monitoring
* Continuous electrocardiogram (ECG) for arrhythmias.
* Frequent blood pressure monitoring (arterial line preferred for precise measurements).
* Central venous pressure (CVP) and pulmonary artery pressures if available.
* Urine output.
* Peripheral perfusion (skin temperature, color, capillary refill).
* Infusion site for signs of extravasation.
* Cardiac output if monitored.
## Clinical Pearls
* Norepinephrine is a potent vasopressor and should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately, do not flush the line, and infiltrate the area with phentolamine.
* Titrate to the lowest effective dose that maintains adequate mean arterial pressure (MAP) and vital organ perfusion.
* Monitor for signs of over-administration (e.g., excessive hypertension, arrhythmias, decreased perfusion) and under-administration (e.g., persistent hypotension, inadequate organ perfusion).
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**Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before making any treatment decisions. Dosing and indications can vary based on patient factors and institutional protocols.
