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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-adrenergic activity (vasoconstriction) and moderate beta-1 adrenergic activity (inotropic effect). It is the first-line vasopressor for most forms of distributive shock.
## Primary Indications
- Hypotension/Shock: First-line agent for septic, cardiogenic, and distributive shock.
## Adult Dosing
- **Initial:** 0.01 to 0.05 mcg/kg/min or 2 to 4 mcg/min via continuous IV infusion.
- **Titration:** Titrate to achieve target mean arterial pressure (MAP), typically ≥65 mmHg.
- **Standard concentration:** 4 mg/250 mL or 8 mg/250 mL (D5W or NS).
- **Maximum dose:** No formal maximum, but doses >1–3 mcg/kg/min are significantly associated with refractory arrhythmias.
## Pediatric Dosing
- **Initial:** 0.05 to 0.1 mcg/kg/min constant infusion.
- **Titration:** Titrate by 0.05 mcg/kg/min every 5–15 minutes as needed.
- **Range:** 0.05 to 2 mcg/kg/min.
*Note: Always consult institutional guidelines or weight-based protocols.*
## Dose Adjustments
- **Hepatic/Renal:** No specific dose adjustments are required; however, close monitoring is essential.
- **Hypovolemia:** Norepinephrine should be avoided or used with extreme caution until hypovolemia is corrected with adequate fluid resuscitation.
## Contraindications
- Hypersensitivity to norepinephrine or sulfites.
- Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary and cerebral perfusion during volume replacement).
- Mesenteric or peripheral vascular thrombosis.
## Adverse Effects
- **Cardiovascular:** Hypertension, bradycardia (reflex), tachyarrhythmias, ischemia (myocardial/peripheral).
- **Extravasation:** Potent vesicant; can cause severe tissue necrosis and sloughing.
- **Metabolic:** Hyperglycemia, metabolic acidosis.
## Key Drug Interactions
- **MAO Inhibitors/Antidepressants:** May cause severe, prolonged hypertension.
- **Beta-blockers:** May result in unopposed alpha-adrenergic stimulation, leading to excessive hypertension and bradycardia.
- **Anesthetics (Halogenated):** May sensitize the myocardium to arrhythmias.
## Monitoring
- **Hemodynamics:** Continuous IV pressure monitoring (arterial line preferred).
- **Vascular Access:** Monitor the infusion site frequently for signs of extravasation. If extravasation occurs, consider phentolamine infiltration.
- **Perfusion:** Monitor urine output, serum lactate, and peripheral perfusion status.
- **Cardiac:** Continuous ECG monitoring for arrhythmias.
## Clinical Pearls
- **Central Line Requirement:** Due to extreme risk of tissue necrosis on extravasation, norepinephrine should be administered via a large central vein whenever possible. In life-threatening emergencies, peripheral administration is permitted but should be in a large vein (antecubital or larger) for the shortest duration possible.
- **Refractory Shock:** If patients are refractory to norepinephrine, consider the addition of vasopressin or corticosteroids per Surviving Sepsis Campaign guidelines.
- **Tapering:** Wean slowly to prevent rebound hypotension.
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*Disclaimer: This information is for educational purposes only. Clinical practice varies by institution and patient-specific factors. Always verify current dosing, compatibility, and infusion protocols with local clinical guidelines and package inserts before prescribing or administering medication.*
