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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine that acts primarily as an alpha-1 adrenergic agonist with some beta-1 adrenergic activity. It causes intense peripheral vasoconstriction and positive inotropic effects, used typically as a first-line vasopressor in distributive shock.
## Primary Indications
- Septic shock
- Hypotension refractory to fluid resuscitation
- Cardiogenic shock (often as an adjunct)
## Adult Dosing
- **Initial:** 0.05 to 0.1 mcg/kg/min or 2 to 4 mcg/min via continuous IV infusion.
- **Titration:** Increase by 0.05–0.1 mcg/kg/min every 3–5 minutes based on mean arterial pressure (MAP) goals (typically MAP ≥65 mmHg).
- **Maintenance:** Generally 0.01 to 3 mcg/kg/min.
- **Maximum:** Theoretically no absolute maximum, but doses exceeding 1–2 mcg/kg/min are associated with severe peripheral ischemia and metabolic acidosis.
## Pediatric Dosing
- **Initial:** 0.05 to 0.1 mcg/kg/min by continuous IV infusion.
- **Titration:** 0.05 mcg/kg/min increments every 3–5 minutes as tolerated.
- **Max dose:** Up to 2 mcg/kg/min.
- *Note:* Always verify concentration (e.g., 0.1 mg/kg in 50 mL fluid = 2 mcg/mL provides 1:1 ratio for mcg/kg/min).
## Dose Adjustments
- No formal renal or hepatic adjustments.
- Reduce titration speed in patients with history of severe peripheral vascular disease or baseline hypertension to prevent acute target organ ischemia.
## Contraindications
- Hypersensitivity to norepinephrine or sulfites.
- Hypotension due to uncorrected hypovolemia (must restore circulating volume first).
- Mesenteric or peripheral vascular thrombosis.
## Adverse Effects
- **Common:** Hypertension, headache, bradycardia (reflexive), anxiety.
- **Serious:** Tissue ischemia/necrosis (secondary to extravasation), cardiac arrhythmias, hyperglycemia, lactic acidosis, mesenteric ischemia.
## Key Drug Interactions
- **MAOIs/Linezolid/TCAs:** May significantly potentiate pressor effects; monitor for hypertensive crisis.
- **Beta-blockers:** May cause severe hypertension and reflex bradycardia due to unopposed alpha-stimulation.
- **Halogenated anesthetics:** Increased risk of ventricular arrhythmias.
## Monitoring
- **Clinical:** Continuous ECG monitoring, mandatory arterial line for precise blood pressure titration, hourly urine output, distal peripheral perfusion (check skin temperature and capillary refill).
- **Laboratory:** Serum lactate levels, CBC, electrolytes (potassium/magnesium), blood glucose.
- **Administration:** Ideally infused via a central venous catheter. If extravasation occurs, immediately stop infusion and consider phentolamine infiltration.
## Clinical Pearls
- **First-line:** Norepinephrine is currently the preferred vasopressor for septic shock per Surviving Sepsis Campaign guidelines.
- **Tachyphylaxis:** May occur with prolonged use; monitor for escalation in dose requirements.
- **Weaning:** Withdraw gradually to avoid rebound hypotension; avoid abrupt discontinuation.
- **Extravasation:** Central venous access is preferred to minimize necrotic risk. If peripherally administered, use the largest available vein and monitor site frequently.
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*Disclaimer: This information is for educational purposes only. Dosing protocols can vary significantly by institution. Always consult your current hospital formulary, local clinical guidelines, and the manufacturer’s package insert before prescribing or administering medication.*
