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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily as an alpha-1 adrenergic agonist with some beta-1 adrenergic activity. It is the preferred first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotension (septic, cardiogenic, or distributive shock).
* Adjunctive therapy for cardiac arrest (rarely used, epinephrine is preferred).
## Adult Dosing
* **Initial:** 0.05 to 0.5 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate to maintain goal Mean Arterial Pressure (MAP), typically ≥ 65 mmHg.
* **Maximum:** No firm pharmacological ceiling; doses > 1–2 mcg/kg/min are significantly associated with refractory shock and increased mortality; clinical judgment and escalation to secondary agents (vasopressin) are recommended.
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min increments to achieve hemodynamic stability.
* **Maximum:** Generally up to 1–2 mcg/kg/min.
* *Note: Always consult institutional guidelines or pediatric ACLS/PALS protocols for weight-based standardization.*
## Dose Adjustments
* **Renal/Hepatic Impairment:** No standard dosage adjustments provided; clinical response dictates required infusion rate.
* **Extravasation Risk:** Reduce dose or switch sites if signs of necrosis occur.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary and cerebral perfusion until fluid replacement therapy is completed).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (tachycardia/bradycardia), myocardial ischemia/infarction.
* **Local:** Tissue necrosis and sloughing (if extravasated).
* **Metabolic:** Metabolic acidosis, hyperglycemia.
* **Other:** Peripheral ischemia (fingers, toes, nose).
## Key Drug Interactions
* **MAO Inhibitors/Antidepressants (TCAs):** Can cause severe, prolonged hypertension.
* **General Anesthetics (e.g., Halogenated hydrocarbons):** Increased risk of ventricular arrhythmias.
* **Beta-blockers:** May result in excessive alpha-adrenergic activity, leading to severe hypertension and reflex bradycardia.
## Monitoring
* **Continuous arterial pressure monitoring:** Strongly recommended for precise titration.
* **Heart rate and ECG:** Monitor for arrhythmias.
* **Perfusion status:** Monitor distal pulses, urine output, skin temperature, and lactate levels.
* **IV site:** Frequent inspection for signs of infiltration.
## Clinical Pearls
* **Administration:** Must be administered via a **central venous line** whenever possible to minimize the risk of severe extravasation injury. If extravasation occurs, consider local infiltration of phentolamine (alpha-blocker) to prevent tissue necrosis.
* **Compatibility:** Administer only via dedicated line or in compatible fluids (typically D5W or D5NS; unstable in normal saline alone over long durations).
* **Refractory Shock:** If requirements exceed institutional thresholds (typically >0.25–0.5 mcg/kg/min), consider adding Vasopressin (0.03–0.04 units/min) or epinephrine rather than continued norepinephrine escalation.
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**Educational Disclaimer:** This information is provided for educational purposes only. Clinical practice is subject to institutional protocols, regional guidelines, and individual patient factors. Always verify current FDA-approved prescribing information and local hospital policies before administering medication.
