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# Norepinephrine
## Overview
Norepinephrine is a vasopressor and inotrope that acts primarily on alpha-1 adrenergic receptors causing vasoconstriction, and to a lesser extent on beta-1 adrenergic receptors in the heart, increasing heart rate and contractility.
## Primary Indications
* Severe hypotension (e.g., shock, septic shock, cardiogenic shock) unresponsive to adequate fluid resuscitation.
## Adult Dosing
* **Typical Dose:** 0.01 to 0.3 mcg/kg/min IV infusion.
* **Initiation:** Often started at 0.05 to 0.1 mcg/kg/min and titrated to achieve target mean arterial pressure (MAP) typically ≥ 65 mmHg.
* **Maximum Dose:** Doses greater than 0.3 mcg/kg/min are generally not recommended due to increased risk of adverse effects.
## Pediatric Dosing
* **Typical Dose:** 0.05 to 0.3 mcg/kg/min IV infusion.
* **Initiation:** Often started at 0.05 mcg/kg/min and titrated.
* **Maximum Dose:** Doses exceeding 1 mcg/kg/min are rarely used and require careful monitoring. Dosing can vary significantly based on patient condition and local protocols.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment, but reduced clearance may occur.
* **Hepatic Impairment:** No specific dose adjustment, but reduced clearance may occur.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe hypotension due to hypovolemia (unless used as a temporizing measure while awaiting fluid resuscitation).
* Use during cyclopropane and halogenated hydrocarbon anesthesia due to potential for severe hypertension and arrhythmias.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), tachycardia, arrhythmias, myocardial ischemia, peripheral ischemia, extravasation leading to tissue necrosis.
* **Other:** Headache, anxiety, dizziness, dyspnea, tremor.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Can potentiate hypertensive crisis. Avoid concurrent use or use with extreme caution and reduced doses.
* **Tricyclic Antidepressants (TCAs) and other drugs that prolong the QTc interval:** May increase risk of arrhythmias.
* **Beta-adrenergic blockers:** May blunt the desired cardiac effects and potentially lead to unopposed alpha-adrenergic stimulation (hypertension).
* **Alpha-adrenergic blockers:** May antagonize the vasoconstrictive effects.
* **Ergot alkaloids:** Increased risk of severe vasoconstriction and ischemia.
* **Oxytocic agents:** May cause severe sustained hypertension.
## Monitoring
* Continuous electrocardiogram (ECG).
* Continuous arterial blood pressure monitoring.
* Urine output.
* Peripheral perfusion (e.g., skin color, temperature, capillary refill).
* Central venous pressure (CVP) or pulmonary artery catheter pressures if indicated.
* Assess for signs of extravasation.
## Clinical Pearls
* Norepinephrine is a potent vasoconstrictor and should be administered via a central venous catheter whenever possible to minimize risk of extravasation.
* If extravasation occurs, stop the infusion immediately and infiltrate the area with phentolamine.
* Titrate infusion rate to achieve the desired hemodynamic goals, not based on a specific dose.
* Withdraw norepinephrine gradually to avoid sudden hypotension.
* The concentration of the infusion can vary; ensure accurate preparation.
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*Disclaimer: This information is intended for clinical professionals. Always consult current prescribing information and relevant clinical guidelines for complete and up-to-date details before making any treatment decisions.*
