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# Norepinephrine
## Overview
Norepinephrine is a potent alpha-adrenergic agonist and a weaker beta-1 adrenergic agonist. It causes peripheral vasoconstriction, leading to increased systemic vascular resistance and blood pressure. It also has a modest increase in cardiac contractility.
## Primary Indications
* Treatment of severe hypotension and shock, particularly distributive shock (e.g., septic shock, neurogenic shock) unresponsive to fluid resuscitation.
* Maintenance of blood pressure during cardiac arrest or other hypotensive emergencies.
## Adult Dosing
* **Administration:** Intravenous infusion.
* **Initial Dose:** Typically started at **2 mcg/min to 10 mcg/min**.
* **Titration:** Titrate infusion rate to achieve desired hemodynamic goals, such as a target mean arterial pressure (MAP) of 65 mmHg or higher, or to maintain adequate organ perfusion.
* **Maximum Dose:** Doses can range up to **0.5 mcg/kg/min** in severe refractory shock, but doses above 1 mcg/kg/min are rarely needed and associated with increased risk. Specific maximums often depend on institutional protocols.
## Pediatric Dosing
* **Administration:** Intravenous infusion.
* **Initial Dose:** Typically started at **0.05 mcg/kg/min to 0.1 mcg/kg/min**.
* **Titration:** Titrate to achieve desired hemodynamic goals, similar to adults.
* **Maximum Dose:** Doses can range up to **2 mcg/kg/min** in refractory shock, but higher doses are associated with significant risk. Specific maximums and titration ranges often depend on institutional protocols and patient response.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential as clearance may be altered.
* **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 halothane (may cause severe hypertension or arrhythmias).
* Severe hypovolemia (must be corrected with fluids first).
* Patients with peripheral or mesenteric vascular thrombosis (risk of increasing ischemia).
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis (requires immediate management with phentolamine).
* **Central Nervous System:** Headache, anxiety, tremor.
* **Other:** Decreased urine output (due to vasoconstriction), dyspnea.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) & Tricyclic Antidepressants (TCAs):** Potentiate the pressor effect, requiring significantly lower initial doses and careful titration.
* **Beta-Blockers:** May block the beta-1 effects of norepinephrine, potentially leading to unopposed alpha-receptor stimulation and severe hypertension.
* **Ergot Alkaloids:** Can cause severe hypertension and peripheral ischemia.
* **Oxytocics:** May cause severe hypertension.
## Monitoring
* **Hemodynamics:** Continuous ECG, frequent blood pressure monitoring (arterial line preferred for continuous infusions), central venous pressure (CVP), and pulmonary artery pressures if available. Assess for signs of adequate organ perfusion (e.g., urine output, mental status, skin temperature).
* **Infusion Site:** Closely monitor for signs of extravasation.
* **Electrolytes:** Especially potassium.
## Clinical Pearls
* Norepinephrine is a potent vasopressor and should be administered via a central venous catheter whenever possible to minimize the risk of extravasation and tissue necrosis.
* Ensure adequate volume resuscitation before initiating norepinephrine, as it is less effective in hypovolemic states and can worsen tissue ischemia.
* Extravasation requires immediate discontinuation of the infusion and infiltration of the affected area with phentolamine.
* Titrate to achieve hemodynamic goals, not just a specific number, considering individual patient factors.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always verify current prescribing information with the official drug monograph and consult with a qualified healthcare provider before making any decisions about patient care.
