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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent. It primarily acts on alpha-1 adrenergic receptors, causing vasoconstriction and increasing systemic vascular resistance (SVR) and blood pressure. It also has some beta-1 adrenergic effects, increasing heart rate and contractility.
## Primary Indications
* Treatment of hypotension, particularly that associated with septic shock and other distributive shock states.
* Restoration and maintenance of blood pressure.
## Adult Dosing
* **Intravenous Infusion:** Typically initiated at 0.01 to 0.02 mcg/kg/min. The dose can be titrated upwards based on the patient's blood pressure response.
* **Typical Therapeutic Range:** 0.01 to 1 mcg/kg/min.
* **Maximum Dose:** Doses exceeding 1 mcg/kg/min may be used in refractory hypotension, but carry a higher risk of adverse effects. Specific maximums are often guided by institutional protocol.
## Pediatric Dosing
* **Intravenous Infusion:** Typically initiated at 0.05 to 0.1 mcg/kg/min. Titrate based on blood pressure and perfusion.
* **Typical Therapeutic Range:** 0.05 to 1 mcg/kg/min.
* **Maximum Dose:** Doses exceeding 1 mcg/kg/min are used in refractory shock and are guided by institutional protocol.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are routinely recommended, but close monitoring is essential.
* **Hepatic Impairment:** No specific dose adjustments are routinely recommended, but close monitoring is essential.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during general anesthesia with cyclopropane or halogenated hydrocarbons (risk of severe hypertension and arrhythmias).
* Hypotension due to factors other than shock (e.g., volume deficit, unless used temporarily until volume resuscitation is complete).
## Adverse Effects
* **Common:** Hypertension, bradycardia (reflex), peripheral ischemia, arrhythmias, anxiety, headache, dizziness, limb pain.
* **Severe:** Extravasation leading to tissue necrosis, elevated lactate, decreased cardiac output, decreased splanchnic blood flow.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiate the pressor response; avoid concurrent use or use extreme caution and significantly reduced doses if necessary.
* **Tricyclic Antidepressants (TCAs):** Potentiate the pressor response; use with caution.
* **Ergot Alkaloids:** May cause severe hypertension and peripheral ischemia.
* **Adrenergic Blockers:** Can antagonize the effects of norepinephrine or lead to unpredictable blood pressure responses.
* **Diuretics:** May potentiate the pressor effects by causing volume depletion.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (arterial line preferred), heart rate, central venous pressure (CVP), pulmonary artery pressures (if available).
* **Perfusion:** Urine output, capillary refill, mental status, lactate levels.
* **Infusion Site:** Assess for signs of extravasation (discoloration, edema, pain).
* **ECG:** For arrhythmias.
## Clinical Pearls
* Norepinephrine is a first-line agent for septic shock and other forms of distributive shock.
* Administer via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, immediately stop the infusion, remove the catheter, and infiltrate the affected area with phentolamine (if available) as per protocol.
* Norepinephrine can decrease splanchnic blood flow at higher doses, potentially worsening gut ischemia.
* Titration should be individualized based on clinical goals (e.g., mean arterial pressure >65 mmHg).
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*Disclaimer: This information is for educational purposes only and does not substitute for professional medical advice. Always consult current prescribing information and institutional guidelines for definitive patient care decisions.*
