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# Norepinephrine
## Overview
Norepinephrine is a sympathomimetic amine that acts primarily as an alpha-adrenergic agonist, causing vasoconstriction, and to a lesser extent, a beta-1 adrenergic agonist, increasing heart rate and contractility. It is used to increase blood pressure.
## Primary Indications
* Treatment of hypotension resulting in inadequate tissue perfusion.
* Cardiogenic shock.
* Septic shock.
## Adult Dosing
**Intravenous infusion:**
* **Initial:** 0.01 to 0.02 mcg/kg/minute.
* **Titration:** Gradually increase dose by 0.01 to 0.02 mcg/kg/minute increments every 5-10 minutes to achieve desired blood pressure (typically systolic BP of 90-100 mmHg or mean arterial pressure (MAP) of 65-75 mmHg, though target may vary based on clinical context and local protocol).
* **Maximum:** Typically 0.1 mcg/kg/minute, but doses up to 0.5 mcg/kg/minute may be used in severe cases.
## Pediatric Dosing
**Intravenous infusion:**
* **Initial:** 0.05 to 0.1 mcg/kg/minute.
* **Titration:** Gradually increase dose by 0.05 to 0.1 mcg/kg/minute increments every 5-10 minutes to achieve desired blood pressure.
* **Maximum:** May be increased up to 1-2 mcg/kg/minute, though higher doses are less common. Specific titration targets and maximums are often guided by institutional protocols.
## Dose Adjustments
No specific dose adjustments are routinely recommended for hepatic or renal impairment, as norepinephrine is rapidly metabolized. However, caution and close monitoring are advised.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during general anesthesia with cyclopropane or halogenated hydrocarbons (risk of severe hypertension, arrhythmias).
* Hypotension due to pure hypovolemia (volume resuscitation should be initiated first).
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, extremity necrosis, extravasation injury.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Metabolic:** Hyperglycemia.
* **Respiratory:** Dyspnea.
## Key Drug Interactions
* **Monoamine oxidase inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Potentiate hypertensive effects; administer with extreme caution or avoid.
* **Beta-adrenergic blockers:** May cause unopposed alpha-adrenergic stimulation leading to severe hypertension.
* **Vasopressors (e.g., phenylephrine, ephedrine):** Additive effects, increased risk of hypertension.
* **Anesthetics (e.g., cyclopropane, halothane):** Increased risk of cardiac arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous ECG monitoring, frequent blood pressure measurements (arterial line preferred for continuous infusion).
* **Infusion site:** Assess for signs of extravasation (pallor, coolness, edema).
* **Urine output:** Monitor for adequate renal perfusion.
* **Lactate levels:** To assess tissue perfusion.
* **Electrolytes and glucose:** Monitor for potential metabolic disturbances.
## Clinical Pearls
* Administer via central venous catheter to minimize risk of extravasation and tissue necrosis. If peripheral IV is necessary, use a large vein and monitor closely, with plans to convert to central line ASAP.
* Phentolamine should be readily available for treatment of extravasation.
* Norepinephrine is light-sensitive; protect infusions from light.
* Gradually taper infusion to avoid abrupt drop in blood pressure.
* Titrate to the lowest effective dose that achieves hemodynamic goals.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols before making any treatment decisions.*
