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# Norepinephrine
## Overview
Norepinephrine is a potent alpha-1 and beta-1 adrenergic agonist. It causes vasoconstriction (increasing peripheral vascular resistance and blood pressure) and increases myocardial contractility.
## Primary Indications
* Cardiogenic shock
* Septic shock and other distributive shock states
* Hypotension unresponsive to fluid resuscitation
## Adult Dosing
Typically initiated as a continuous infusion.
* **Starting Dose:** 0.01 to 0.05 mcg/kg/minute.
* **Titration:** Increase dose every few minutes based on hemodynamic response (e.g., mean arterial pressure \[MAP] > 65 mmHg).
* **Maximum Dose:** Commonly cited maximum is 2 mcg/kg/minute, though higher doses may be used in refractory shock. Specific maximums can vary by institution.
## Pediatric Dosing
Dosing varies widely and depends on the specific clinical scenario and institutional protocol.
* **Loading Dose (if used):** 0.1 to 0.2 mcg/kg/minute (often given over 10 minutes).
* **Maintenance Infusion:** 0.05 to 1 mcg/kg/minute.
* **Titration:** Titrate to achieve target MAP for age (e.g., MAP > gestational age + 2 years).
* **Maximum Dose:** Often up to 1-2 mcg/kg/minute, but may exceed this based on response and protocol.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment, but prolonged use may require careful monitoring for potential accumulation or side effects.
* **Hepatic Impairment:** No specific dose adjustment, but careful titration is recommended.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during cyclopropane or halogenated hydrocarbon anesthesia (risk of severe hypertension or arrhythmias).
## Adverse Effects
* **Cardiovascular:** Arrhythmias (tachycardia, bradycardia, ventricular arrhythmias), hypertension, peripheral ischemia, tissue necrosis (especially with extravasation), reflex bradycardia.
* **Other:** Anxiety, headache, dizziness, apprehension, dyspnea, piloerection.
## Key Drug Interactions
* **MAO Inhibitors & Tricyclic Antidepressants:** Potentiate the pressor effect. Avoid concurrent use or use with extreme caution and reduced initial doses.
* **Beta-blockers:** Can unmask or worsen unopposed alpha-adrenergic effects (severe hypertension, vasoconstriction).
* **Alpha-blockers:** Can reduce the pressor effect.
* **Oxytocics:** May potentiate the pressor effect and cause severe hypertension.
* **Ergot alkaloids:** May potentiate the pressor effect.
## Monitoring
* **Hemodynamics:** Frequent monitoring of blood pressure (arterial line preferred), heart rate, cardiac rhythm.
* **Perfusion:** Urine output, skin color and temperature, capillary refill, mental status.
* **Infusion Site:** Closely monitor for signs of extravasation.
## Clinical Pearls
* Norepinephrine is a potent vasopressor and requires careful, continuous infusion and close monitoring.
* Always administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, stop the infusion immediately and infiltrate the area with phentolamine (an alpha-blocker) to prevent tissue damage.
* Titrate to achieve target MAP, not necessarily a specific number, considering organ perfusion.
* In septic shock, norepinephrine is often the first-line vasopressor.
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*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 guidelines before administering any medication.*
