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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine possessing both alpha-1 adrenergic (vasoconstriction) and beta-1 adrenergic (inotropic) activity. It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states (e.g., septic, cardiogenic, neurogenic shock)
* Adjunct in the treatment of cardiac arrest
## Adult Dosing
* **Continuous Infusion:** Initiate at 0.01–0.05 mcg/kg/min (or 2–5 mcg/min fixed dose).
* **Titration:** Titrate to clinical effect (target Mean Arterial Pressure, typically 65 mmHg) in increments of 0.05–0.1 mcg/kg/min every 2–5 minutes.
* **Typical Refractory Range:** 0.1–3 mcg/kg/min; doses exceeding 1 mcg/kg/min often require a second agent (e.g., vasopressin).
## Pediatric Dosing
* **Continuous Infusion:** 0.05–2 mcg/kg/min.
* **Note:** Dosing is highly protocol-dependent; consult institutional guidelines for specific titration steps and weight-based concentration requirements.
## Dose Adjustments
* **Renal/Hepatic:** No specific dose adjustments provided; use with caution in patients with severe underlying disease.
* **Extravasation Risk:** Reduce dosage or discontinue infusion if infiltration occurs.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary and cerebral perfusion until volume replacement is completed).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, myocardial ischemia.
* **Local:** Extravasation necrosis (peripheral tissue ischemia).
* **Other:** Metabolic acidosis, anxiety, headache.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May cause severe, prolonged hypertension; dose reduction of norepinephrine is recommended.
* **Beta-Blockers:** May decrease the inotropic effects of norepinephrine and result in unopposed alpha-mediated vasoconstriction.
* **Halogenated Anesthetics:** May sensitize the myocardium to arrhythmias.
## Monitoring
* **Continuous arterial pressure monitoring** is strongly recommended for prolonged or high-dose infusions.
* **Assessment of perfusion:** Heart rate, rhythm, urine output, and skin integrity at the infusion site.
* **Metabolic:** Monitor lactate and venous oxygen saturation to ensure adequate end-organ perfusion.
## Clinical Pearls
* **Central access preferred:** If administered peripherally, use a large, proximal vein (avoid distal extremities/hand) and limit duration; monitor site continuously for blanching or coldness.
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately and infiltrate the area with **phentolamine** (5–10 mg in 10 mL saline) locally to prevent necrosis.
* **Weaning:** Wean slowly to avoid rebound hypotension; consider volume status before attempting to discontinue.
* **Dose calculation:** Always use a weight-based protocol if available to minimize medication errors.
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**Disclaimer:** This information is for educational purposes only. Clinical settings and institutional protocols vary widely. Always verify current prescribing information, package inserts, and hospital-specific guidelines prior to administering medication.
