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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 adrenergic receptors (inotropy). It is the first-line vasopressor for distributive shock.
## Primary Indications
* Hypotension associated with septic shock
* Acute hypotensive states (e.g., cardiogenic or neurogenic shock)
* Adjunct in cardiac arrest (if return of spontaneous circulation is achieved but hypotension persists)
## Adult Dosing
* **Initial:** 0.01 to 0.05 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.01 to 0.05 mcg/kg/min every 2–5 minutes to achieve target mean arterial pressure (MAP) (typically >65 mmHg).
* **Maintenance:** Generally 0.01 to 3 mcg/kg/min, though refractory shock may require higher doses.
* **Note:** Dosing varies significantly by institutional protocol.
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate to clinical effect.
* **Max:** Generally considered 2 mcg/kg/min, but practice varies based on resuscitation guidelines (e.g., PALS).
## Dose Adjustments
* **Renal/Hepatic:** No specific dosage adjustments established.
* **Titration:** Taper doses gradually to avoid precipitous hemodynamic collapse (rebound hypotension).
## Contraindications
* Hypersensitivity to norepinephrine (or sulfites).
* Hypotension due to uncorrected blood volume deficit (except as emergency support during fluid resuscitation).
* Mesenteric or peripheral vascular thrombosis (due to risk of increasing ischemia).
## Adverse Effects
* **Common:** Hypertension, headache, bradycardia (reflex).
* **Serious:** Extravasation injury (tissue necrosis), arrhythmias, peripheral ischemia/necrosis (toes, digits), lactic acidosis, mesenteric ischemia.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May cause severe, prolonged hypertension due to inhibited metabolism/uptake.
* **Alpha-blockers:** May antagonize the vasoconstrictive effects of norepinephrine.
* **Beta-blockers:** May result in unopposed alpha-adrenergic vasoconstriction and severe hypertension.
## Monitoring
* **Hemodynamics:** Continuous invasive blood pressure (A-line) preferred.
* **Access:** Pulse/perfusion distal to IV site frequently.
* **Metabolic:** Lactate levels, venous oxygen saturation (ScvO2/SvO2), and urine output.
## Clinical Pearls
* **Extravasation Risk:** Must be administered via a **central venous line** whenever possible. If peripheral use is necessary, use the most proximal vein possible and monitor for signs of infiltration.
* **Management of Extravasation:** If infiltration occurs, infiltrate the site with **phentolamine** (alpha-adrenergic antagonist) as soon as possible.
* **Compatibility:** Must be administered in compatible IV fluids; check Y-site compatibility before hanging with other infusions.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practices vary by institution. Always consult your facility’s specific drug monographs, local protocols, and current prescribing information before administering medications.
