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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine primarily acting on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 adrenergic receptors (inotropic effect). It is the first-line vasopressor for septic and vasodilatory shock.
## Primary Indications
* Acute hypotension (e.g., septic, cardiogenic, or distributive shock).
* Adjunct treatment of cardiac arrest (off-label/specialized protocols).
## Adult Dosing
* **Initial Dose:** 0.01 to 0.05 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.01–0.05 mcg/kg/min every 3–5 minutes to achieve target Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Maintenance Dose:** 0.05 to 0.5 mcg/kg/min titration to effect.
* **Maximum Dose:** Generally 1–3 mcg/kg/min; higher doses provide diminishing returns and increase risk of severe tissue ischemia.
## Pediatric Dosing
* **Initial Dose:** 0.05 to 0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.05 mcg/kg/min every 5–10 minutes.
* **Maintenance:** Usual range 0.05 to 1 mcg/kg/min.
* **Note:** Pediatric dosing is highly institutional-protocol dependent. Use weight-based calculations carefully.
## Dose Adjustments
* **Renal/Hepatic:** No formal dose adjustments required; however, close monitoring is essential due to the underlying severity of shock.
* **Discontinuation:** Wean gradually to prevent rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension secondary to uncorrected hypovolemia (must replace volume before/concurrently with pressors).
* Mesenteric or peripheral vascular thrombosis (caution).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (tachycardia or bradycardia), myocardial ischemia.
* **Local:** Extravasation can cause severe tissue necrosis and sloughing.
* **Systemic:** Peripheral/visceral ischemia, bradycardia (reflex), anxiety, headache.
## Key Drug Interactions
* **MAO Inhibitors/Antidepressants:** May cause severe, prolonged hypertension.
* **Beta-blockers:** May result in unopposed alpha-adrenergic vasoconstriction, leading to extreme hypertension and reflex bradycardia.
* **General Anesthetics:** Potential for sensitization of the myocardium to arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous invasive arterial blood pressure monitoring (preferred) or frequent non-invasive BP checks.
* **Perfusion:** MAP, heart rate, EKG (arrhythmia monitoring), urine output, lactate levels, and core-to-extremity perfusion gradients.
* **Access Site:** Inspect IV site frequently for signs of infiltration.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately. If available, infiltrate the area with phentolamine (5–10 mg in 10 mL saline) locally to prevent necrosis.
* **Access:** Highly preferred via central venous catheter to reduce risk of extravasation, though peripheral administration is acceptable for short durations through large-bore, proximal veins.
* **Compatibility:** Must be infused via a dedicated line. Do not mix with other drugs in the same line.
* **Shock State:** Norepinephrine is not a substitute for volume resuscitation; ensure adequate fluid loading unless contraindicated (e.g., severe heart failure).
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**Disclaimer:** This information is for educational purposes and does not replace local clinical protocols or institutional guidelines. Dosing and safety standards may evolve; always verify prescribing information with the latest clinical resources or pharmacy department before administration.
