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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent. It acts primarily on alpha-adrenergic receptors, causing peripheral vasoconstriction, which increases systemic vascular resistance and blood pressure. It also has some beta-1 adrenergic effects, increasing heart rate and contractility.
## Primary Indications
* Treatment of severe hypotension and shock, particularly septic shock and cardiogenic shock, when other treatments have failed or are insufficient.
## Adult Dosing
* **Initial Dose:** 2 to 10 mcg/minute infused intravenously.
* **Titration:** Increase infusion rate as needed to maintain target blood pressure (e.g., systolic blood pressure of 90-100 mmHg or mean arterial pressure of 65-75 mmHg). Doses may be increased up to 30 mcg/minute or higher in some cases, guided by patient response.
* **Local protocols** dictate specific target blood pressures and titration parameters.
## Pediatric Dosing
* **Initial Dose:** 0.05 to 0.1 mcg/kg/minute infused intravenously.
* **Titration:** Increase infusion rate as needed to maintain target blood pressure. Doses may be increased up to 1 mcg/kg/minute or higher.
* **Pediatric dosing** is highly variable and **local protocols** must be followed.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but close monitoring is essential due to potential accumulation and increased sensitivity.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but close monitoring is essential due to potential accumulation and increased sensitivity.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use as the sole agent to maintain blood pressure in patients with profound volume deficit (i.e., before volume resuscitation is initiated).
* Use during cyclopropane or halogenated hydrocarbon anesthesia (risk of severe arrhythmias).
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis (most serious).
* **Central Nervous System:** Headache, anxiety, dizziness, tremors.
* **Other:** Dyspnea, nausea, vomiting.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Potentiate the pressor effect of norepinephrine; avoid concurrent use or use with extreme caution and reduced doses if necessary.
* **General Anesthetics (e.g., halothane, enflurane):** Can increase myocardial irritability and sensitization to catecholamines, leading to arrhythmias.
* **Beta-adrenergic Blockers:** May blunt the beta-1 effects of norepinephrine, potentially leading to unopposed alpha-adrenergic vasoconstriction and severe hypertension.
* **Alpha-adrenergic Blockers:** May reduce the pressor effect.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (arterial line preferred), heart rate, central venous pressure, pulmonary artery pressures (if available).
* **Perfusion:** Urine output, mental status, peripheral circulation, lactate levels.
* **Extravasation:** Frequent inspection of the IV insertion site. Have phentolamine readily available for potential extravasation management.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* Always ensure adequate volume resuscitation before initiating or titrating norepinephrine.
* Extravasation management: Immediately stop the infusion, aspirate residual drug, and infiltrate the area with phentolamine (an alpha-adrenergic blocker).
* Wean norepinephrine gradually to avoid abrupt hypotension.
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*This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for complete and up-to-date details before making treatment decisions.*
