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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 systemic vascular resistance. It also has some beta-1 adrenergic activity, leading to increased heart rate and contractility.
## Primary Indications
* Treatment of hypotension, particularly in the setting of septic shock and other distributive shock states.
## Adult Dosing
* **Initial Dose:** 0.01 to 0.02 mcg/kg/min intravenously.
* **Maintenance Dose:** Titrate to achieve target mean arterial pressure (MAP) of 65 mmHg or higher. Doses can range from 0.01 to 0.3 mcg/kg/min, with higher doses sometimes required in severe shock.
* **Maximum Dose:** Doses exceeding 0.3 mcg/kg/min are generally not recommended due to increased risk of adverse effects, but may be used in extreme circumstances under expert guidance. Exact maximums depend on local protocol and patient response.
## Pediatric Dosing
* **Initial Dose:** 0.05 to 0.1 mcg/kg/min intravenously.
* **Maintenance Dose:** Titrate to achieve target MAP (e.g., > gestational age + 2 years in neonates, or > 50 mmHg in older children). Doses can range from 0.05 to 2 mcg/kg/min.
* **Maximum Dose:** Typically 2 mcg/kg/min, though higher doses may be necessary. Exact maximums depend on local protocol and patient response.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential.
* **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).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia, arrhythmias, peripheral ischemia, myocardial infarction, palpitations.
* **Local:** Extravasation leading to tissue necrosis.
* **Other:** Headache, anxiety, tremors, dyspnea.
## Key Drug Interactions
* **MAO Inhibitors and Tricyclic Antidepressants:** Potentiate the pressor effect of norepinephrine, leading to severe hypertension. Discontinue MAOIs at least 14 days prior to norepinephrine initiation.
* **General Anesthetics (e.g., Halothane, Cyclopropane):** Increased risk of arrhythmias.
* **Beta-blockers:** May unopposed alpha-adrenergic stimulation, leading to severe hypertension.
* **Alpha-blockers:** May decrease pressor effect.
## Monitoring
* **Hemodynamics:** Continuous ECG monitoring, frequent blood pressure measurements (arterial line preferred), central venous pressure, pulmonary artery pressures (if available).
* **Perfusion:** Urine output, mental status, skin temperature, capillary refill.
* **Metabolic:** Serum lactate, blood glucose.
* **Infusion Site:** Regular assessment for signs of extravasation.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately and infiltrate the affected area with phentolamine.
* Titrate infusion rate based on MAP, not heart rate.
* Short half-life necessitates continuous infusion; abrupt discontinuation can lead to profound hypotension.
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*Disclaimer: This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions.*
