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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 (inotropic effect). It is the first-line vasopressor for distributive (septic) shock.
## Primary Indications
* First-line treatment for hypotension in septic, distributive, or cardiogenic shock.
* Adjunctive therapy for critical hypotension refractory to fluid resuscitation.
## Adult Dosing
* **Initial:** 0.05–0.1 mcg/kg/min (or 2–4 mcg/min fixed dose).
* **Titration:** Titrate by 0.05–0.2 mcg/kg/min every 3–5 minutes based on Mean Arterial Pressure (MAP) goals (typically MAP ≥ 65 mmHg).
* **Maintenance:** Generally 0.01–3 mcg/kg/min.
* **Maximum:** No established pharmacological maximum; however, doses >1–2 mcg/kg/min are associated with significant tissue ischemia and peripheral vasoconstriction.
## Pediatric Dosing
* **Initial:** 0.05–0.1 mcg/kg/min.
* **Titration:** Titrate to maintain age-appropriate blood pressure/MAP goals per institutional protocol.
* **Note:** Always verify pediatric weight-based calculations via pharmacy-approved dosing tools.
## Dose Adjustments
* **Renal/Hepatic:** No specific dose adjustments required; however, monitor closely for tissue perfusion deficits in patients with pre-existing organ failure.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected hypovolemia (must restore volume status).
* Mesenteric or peripheral vascular thrombosis (risk of worsening ischemia).
## Adverse Effects
* **Extravasation:** Causes severe tissue necrosis and sloughing (treat with phentolamine infiltration).
* **Cardiovascular:** Hypertension, tachyarrhythmias, bradycardia (reflex), limb ischemia.
* **Other:** Metabolic acidosis, anxiety, headache.
## Key Drug Interactions
* **MAO Inhibitors/TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-blockers:** May cause excessive alpha-adrenergic stimulation leading to vasoconstriction and reflex hypertension.
* **Halogenated Anesthetics:** Increased risk of ventricular arrhythmias due to myocardial sensitization.
## Monitoring
* **Continuous ECG:** Monitor for arrhythmias.
* **Hemodynamics:** MAP, heart rate, and urine output (via arterial line preferred).
* **Site:** Inspect infusion site frequently for patency; if possible, administer via central venous catheter to prevent extravasation.
* **Perfusion:** Monitor distal extremity temperature, color, and capillary refill.
## Clinical Pearls
* **Central access required:** Use central venous access whenever possible. If administered via peripheral line, use a large vein (antecubital or larger) and monitor for infiltration continuously.
* **Fluid status:** Norepinephrine cannot replace volume; ensure adequate intravascular volume is achieved to optimize vasopressor response.
* **Weaning:** When weaning, maintain hemodynamic stability by ensuring fluid resuscitation is adequate to prevent rebound hypotension.
* **Institutional Protocols:** Specific infusion concentrations (e.g., 4 mg/250 mL or 8 mg/250 mL) and titrations are strictly defined by institutional policy.
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*Disclaimer: This information is for educational purposes only. Clinical practice varies by institution. Always verify current prescribing information, institutional guidelines, and drug compatibility before administration.*
