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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent that acts primarily on alpha-1 adrenergic receptors, causing vasoconstriction, and on beta-1 adrenergic receptors, increasing heart rate and contractility. It is a naturally occurring catecholamine.
## Primary Indications
* Severe hypotension (e.g., shock, sepsis) refractory to fluid resuscitation.
* Cardiogenic shock.
## Adult Dosing
* **Initial Rate:** 0.01 to 0.02 mcg/kg/min IV infusion.
* **Titration:** Titrate slowly to achieve desired mean arterial pressure (MAP) (e.g., target MAP $\ge$ 65 mmHg).
* **Maximum Dose:** Typically 0.1 mcg/kg/min, but higher doses may be used cautiously in refractory shock. Doses $\ge$ 0.3 mcg/kg/min are considered very high and require careful consideration.
* **Preparation:** Dilute in a compatible IV fluid (e.g., D5W, NS). Common concentrations range from 4 mcg/mL to 16 mcg/mL. *Confirm local preparation guidelines.*
## Pediatric Dosing
* **Initial Rate:** 0.05 to 0.1 mcg/kg/min IV infusion.
* **Titration:** Titrate to achieve target MAP for age (e.g., $\ge$ 40 mmHg for neonates, $\ge$ 50 mmHg for infants, $\ge$ 60 mmHg for children).
* **Maximum Dose:** 1-2 mcg/kg/min.
* **Preparation:** Dilute in D5W or NS. Common concentrations are 20 mcg/mL or 40 mcg/mL. *Confirm local preparation guidelines.*
## Dose Adjustments
No specific dose adjustments for hepatic or renal impairment are established. Dosing is guided by hemodynamic response.
## Contraindications
* Hypersensitivity to norepinephrine.
* In patients with existing severe peripheral vascular thrombosis (due to risk of worsening ischemia).
## Adverse Effects
* **Cardiovascular:** Arrhythmias (tachycardia, bradycardia), hypertension, peripheral ischemia, gangrene, angina, decreased cardiac output.
* **Central Nervous System:** Headache, anxiety, dizziness.
* **Local:** Extravasation can cause severe tissue necrosis; antidote is phentolamine.
## Key Drug Interactions
* **Anesthetics:** May potentiate arrhythmias, especially with halogenated anesthetics.
* **Beta-blockers:** May cause unopposed alpha-stimulation, leading to severe hypertension.
* **MAO inhibitors & Tricyclic Antidepressants:** Can prolong and intensify the pressor effect. Avoid concurrent use.
* **Oxytocics:** May cause severe hypertension.
## Monitoring
* **Hemodynamic:** Continuous arterial blood pressure, heart rate, central venous pressure (CVP), pulmonary artery pressures (if available).
* **Urine Output:** Monitor for adequate renal perfusion.
* **Peripheral Perfusion:** Assess skin color, temperature, capillary refill, and presence of pulses.
* **Lactate levels:** To assess tissue perfusion.
* **ECG:** For arrhythmias.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize risk of extravasation and tissue injury.
* If extravasation occurs, stop infusion immediately, do not flush, and administer phentolamine subcutaneously to the affected area.
* Gradually taper infusion to avoid rebound hypotension.
* Consider concurrent use of other agents (e.g., vasopressin, dobutamine) based on clinical scenario and patient response.
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*Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information and consult relevant guidelines and drug monographs for complete details and updates.*
