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# Norepinephrine
## Overview
Norepinephrine is a sympathomimetic amine that acts as a potent vasoconstrictor and inotropic agent, primarily through alpha-adrenergic receptor stimulation.
## Primary Indications
* Treatment of severe hypotension and shock.
* Adjunct to fluid resuscitation in septic shock and other distributive shock states.
## Adult Dosing
* **Starting Dose:** 0.01 to 0.02 mcg/kg/min IV infusion.
* **Titration:** Gradually increase by 0.01 to 0.02 mcg/kg/min every 5-15 minutes as needed to achieve target mean arterial pressure (MAP) of at least 65 mmHg.
* **Maximum Dose:** Generally not to exceed 0.1 mcg/kg/min, but higher doses may be used in refractory shock under expert guidance. Local protocols often define maximums.
## Pediatric Dosing
* **Starting Dose:** 0.05 to 0.1 mcg/kg/min IV infusion.
* **Titration:** Gradually increase by 0.05 to 0.1 mcg/kg/min every 5-15 minutes as needed.
* **Maximum Dose:** Generally not to exceed 1 mcg/kg/min. Precise dosing and titration are often guided by local pediatric critical care protocols.
## Dose Adjustments
* No specific dose adjustments are typically required for hepatic or renal impairment, as the drug is extensively metabolized and its effects are primarily hemodynamic. However, close monitoring of response is crucial in these populations.
## Contraindications
* Hypersensitivity to norepinephrine.
* Concurrent use with cyclopropane and halothane anesthetics (risk of severe hypertension and arrhythmias).
## Adverse Effects
* **Cardiovascular:** Hypertensive crisis, bradycardia (reflex), arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Other:** Dyspnea, nausea, vomiting.
## Key Drug Interactions
* **MAO Inhibitors & Tricyclic Antidepressants:** Potentiate hypertensive crisis; discontinue MAOIs at least 14 days prior to norepinephrine initiation.
* **Alpha and Beta Blockers:** May antagonize effects or lead to complex hemodynamic responses.
* **Ergot Alkaloids & Oxytocics:** May cause severe prolonged hypertension.
* **Anesthetics (e.g., Halothane, Cyclopropane):** Increased risk of arrhythmias.
## Monitoring
* **Hemodynamic parameters:** Continuous blood pressure (arterial line preferred), heart rate, cardiac output (if available).
* **Urine output:** Assess renal perfusion.
* **Peripheral circulation:** Monitor for signs of ischemia (e.g., skin color, temperature, capillary refill).
* **Infusion site:** Inspect regularly for signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to reduce the risk of peripheral vasoconstriction and extravasation.
* If extravasation occurs, stop the infusion and administer phentolamine subcutaneously to the affected area.
* Titrate to the lowest effective dose to achieve hemodynamic goals and minimize adverse effects.
* Norepinephrine should be infused through dedicated IV lines or Y-sites closest to the heart to prevent co-administration with alkaline solutions.
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*Please verify this information with the most current prescribing information available from the manufacturer and relevant clinical guidelines.*
