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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-adrenergic activity (vasoconstriction) and moderate beta-1-adrenergic activity (increased inotropy). It is primarily used as a first-line vasopressor for distributive shock.
## Primary Indications
* Septic shock.
* Hypotension refractory to fluid resuscitation.
* Cardiogenic shock (often as an adjunct).
## Adult Dosing
* **Initial:** 0.01 to 0.05 mcg/kg/min (or 2–4 mcg/min fixed-rate equivalent).
* **Titration:** Titrate every 2–5 minutes to achieve target Mean Arterial Pressure (MAP), typically 65 mmHg.
* **Typical Maintenance:** 0.05 to 0.5 mcg/kg/min.
* **Maximum:** No defined absolute maximum; requirements >1–3 mcg/kg/min are considered highly refractory and suggest poor prognosis.
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min IV infusion.
* **Titration:** Increase to effect; usual range up to 1 mcg/kg/min.
* **Note:** Dosing varies strictly by institutional protocols and the urgency of the clinical scenario.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No specific adjustment required; however, use with caution and monitor for prolonged hemodynamic instability.
* **Elderly:** Use lowest effective dose; higher risk of peripheral ischemia.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to uncorrected hypovolemia (must restore volume status first).
* Thrombosis (e.g., mesenteric, peripheral vascular) may be exacerbated by vasoconstriction.
## Adverse Effects
* **Cardiovascular:** Bradycardia (reflex), arrhythmias, myocardial ischemia, hypertension.
* **Extravasation:** Tissue necrosis and sloughing (if leakage occurs).
* **Metabolic:** Lactic acidosis (secondary to peripheral vasoconstriction/hypoperfusion).
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May result in severe, prolonged hypertensive crisis.
* **Beta-blockers:** May lead to excessive alpha-mediated vasoconstriction (unopposed alpha-stimulation).
* **Halogenated Anesthetics:** May sensitize the myocardium to arrhythmias.
## Monitoring
* **Continuous:** ECG (arrhythmias) and invasive blood pressure monitoring (art-line) preferred.
* **Perfusion:** Vital signs, urine output, serum lactate, and peripheral perfusion (to assess for ischemia).
* **Site:** Inspect IV site frequently for signs of extravasation. Use a large-bore central venous catheter whenever possible.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately. Phentolamine infiltration is the standard treatment to antagonize the vasoconstriction.
* **Line Compatibility:** Central venous access is strongly preferred to avoid skin necrosis, though short-term use in large peripheral veins may be tolerated under strict institutional protocols.
* **Tapering:** Wean slowly to avoid rapid hemodynamic collapse.
* **Refractory Cases:** If vasopressor requirements rise, consider adding vasopressin (0.03–0.04 units/min) or evaluating for adrenal insufficiency.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult your institutional formulary, clinical guidelines, and the official manufacturer's prescribing information before prescribing or administering any medication.
