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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine that acts as a vasopressor. It primarily stimulates alpha-1 adrenergic receptors, causing peripheral vasoconstriction and increasing systemic vascular resistance. It also has some beta-1 adrenergic receptor activity, leading to increased cardiac contractility.
## Primary Indications
* Severe Hypotension (e.g., shock, septic shock, neurogenic shock) refractory to fluid resuscitation.
## Adult Dosing
* **Initial infusion rate:** 0.01 to 0.1 mcg/kg/min.
* **Titration:** Titrate infusion rate upwards to achieve target mean arterial pressure (MAP), typically greater than 65 mmHg.
* **Maximum infusion rate:** Doses up to 1 mcg/kg/min have been used, but higher doses may be associated with increased risk of adverse effects. Local protocols may specify higher maximums.
## Pediatric Dosing
* **Initial infusion rate:** 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate infusion rate to achieve target MAP or clinical goals.
* **Maximum infusion rate:** Generally considered up to 1 mcg/kg/min, but higher doses may be necessary in certain critical situations. Consult pediatric critical care guidelines.
## Dose Adjustments
* No dose adjustments are typically required for hepatic or renal impairment, as norepinephrine is metabolized primarily in the liver and excreted by the kidneys, but its effects are local when infused intravenously.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe uncorrected hypovolemia.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis.
* **Other:** Headache, anxiety, tremor, dyspnea.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiated hypertensive response. Discontinue MAOIs at least 14 days prior to starting norepinephrine.
* **Tricyclic Antidepressants (TCAs):** Potentiated hypertensive response. Use with caution.
* **General Anesthetics:** Increased risk of arrhythmias. Use with extreme caution.
* **Beta-blockers:** May potentiate unopposed alpha-receptor stimulation, leading to severe hypertension.
## Monitoring
* **Hemodynamics:** Continuous ECG, frequent blood pressure monitoring (arterial line preferred for titratable infusions), central venous pressure (if available).
* **Urine Output:** Monitor for adequate renal perfusion.
* **Extremity Perfusion:** Assess for signs of peripheral ischemia (e.g., color, temperature, capillary refill).
* **Infusion Site:** Monitor closely for signs of extravasation.
## Clinical Pearls
* Norepinephrine should be infused through a central venous catheter to minimize the risk of extravasation and subsequent tissue necrosis.
* If extravasation occurs, stop the infusion immediately, do not flush the line, and administer phentolamine infiltrated into the affected area.
* Concurrent administration with other vasopressors or inotropes should be carefully considered and guided by institutional protocols.
* Titration should be guided by the patient's clinical response and hemodynamic parameters.
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**Disclaimer:** This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and your healthcare provider for any medical decisions.
