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# Norepinephrine
## Overview
Norepinephrine is a vasopressor that acts primarily on alpha-1 adrenergic receptors, causing peripheral vasoconstriction and increasing blood pressure. It also has some beta-1 adrenergic receptor activity, which can increase heart rate and contractility.
## Primary Indications
* Severe hypotension and shock (e.g., septic shock, cardiogenic shock) unresponsive to fluid resuscitation.
## Adult Dosing
* **Intravenous infusion:** Typically initiated at **2 to 4 mcg/minute** (0.02 to 0.1 mcg/kg/minute) via a central venous catheter.
* **Titration:** Titrate to achieve and maintain a target mean arterial pressure (MAP) of **65 mmHg** or higher, or as per local protocol. Doses may be increased gradually every 2-5 minutes.
* **Maximum dose:** Doses can range up to **0.2 to 0.5 mcg/kg/minute**, depending on patient response and clinical situation, but higher doses are associated with increased risk of adverse events. Specific maximums are often dictated by institutional guidelines and clinical judgment.
## Pediatric Dosing
* **Intravenous infusion:** Typically initiated at **0.05 to 0.1 mcg/kg/minute**.
* **Titration:** Titrate to achieve and maintain a target MAP greater than or equal to the patient's gestational age plus 5 mmHg (in neonates) or greater than or equal to 50 mmHg (in older children), or as per local protocol. Doses may be increased in increments of 0.05 to 0.1 mcg/kg/minute every 5-10 minutes.
* **Maximum dose:** Doses may be increased up to **2 mcg/kg/minute** in refractory cases.
## Dose Adjustments
* No specific dose adjustments are required for renal or hepatic impairment, as norepinephrine is rapidly metabolized. However, close monitoring of hemodynamic parameters is essential in all patients.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to absolute or relative hypovolemia (should be corrected with volume resuscitation first).
* In all cases, the benefits of norepinephrine should be weighed against the risks.
## Adverse Effects
* **Cardiovascular:** Arrhythmias (including ventricular arrhythmias), tachycardia, bradycardia, hypertension, peripheral ischemia, decreased cardiac output, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremors.
* **Other:** Increased blood glucose, decreased urine output.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiated hypertensive crisis. Avoid concurrent use.
* **Tricyclic Antidepressants (TCAs) and other drugs that inhibit norepinephrine reuptake:** May potentiate the pressor response. Use with caution and monitor blood pressure closely.
* **Anesthetics (e.g., halothane):** Increased risk of arrhythmias.
## Monitoring
* Continuous electrocardiogram (ECG).
* Continuous blood pressure monitoring (arterial line preferred).
* Central venous pressure.
* Urine output.
* Peripheral perfusion (e.g., skin temperature, capillary refill, color).
* Mental status.
* Serum lactate and acid-base status.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter to reduce the risk of extravasation and local tissue necrosis.
* If extravasation occurs, stop the infusion immediately and infiltrate the affected area with phentolamine (an alpha-adrenergic blocker).
* Gradually taper norepinephrine infusion to avoid sudden drops in blood pressure.
* In septic shock, norepinephrine is often the first-line vasopressor.
* Ensure adequate volume status before and during norepinephrine administration.
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*Disclaimer: This information is intended for clinical decision support and does not replace professional medical judgment. Always consult the most current prescribing information and institutional guidelines before administering any medication.*
