Lecture on Norepinephrine in Critical Care

Introduction

• Medication widely used in critical care
• Important for patient care
• Lesson by Eddie Watson from ICU Advantage
• Goal: Simplify complex critical care subjects
• Notes available to YouTube and Patreon members
• Quizzes available on icuadvantage.com with weekly giveaways

What is Norepinephrine?

• Also known as norepi or Levafed (trade name), noradrenaline (outside the US)
• Same as natural hormone and neurotransmitter in body
• Sympathomimetic medication: Mimics endogenous hormone effects on sympathetic nervous system
• Classified as a vasopressor: Increases blood pressure

Mechanism of Action

• Activates receptors of the sympathetic nervous system
• Works by activating alpha (α) and beta (β) adrenergic receptors
  • Alpha Receptors: Effects on α1 and α2 receptors
    • Smooth muscle contraction in arteries and veins
    • Increases systemic vascular resistance -> Higher blood pressure
  • Beta Receptors: Effects on β1, β2, and β3 receptors
    • Beta 1 (β1): Heart effects (positive chronotropic and inotropic)
    • Beta 2 (β2): Smooth muscle relaxation in airways, arteries
    • Full receptor activation -> Overall increase in blood pressure

Clinical Effects

• Increases systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), mean arterial pressure (MAP), central venous pressure (CVP), heart rate, and cardiac output
• Note on tachycardia: Can lead to reduced cardiac output due to insufficient filling time
• Effectiveness affected by concentration, temperature, and patient’s pH (acidosis reduces effectiveness)

Dosing

• Short half-life: 2.5 minutes
• Administration: Continuous IV infusion
• Preferred via central line; can be given via peripheral IV (large vein)
• Concentrations: 4, 8, 16, 32 mg in 250 mL (pre-mixed or manual)
• Dosing range: Generally 1-50 mcg/min (0.025-1 mcg/kg/min for weight-based)
• Starting dose: 5-10 mcg/min or 0.05 mcg/kg/min
• Titration: Facility-dependent; reference previous vasopressors lesson

Adverse Effects

• Excessive vasoconstriction -> Decreased organ perfusion, hypertension
• Tachycardia, arrhythmias
• Baroreceptor-mediated bradycardia
• Negative effects in patients with pulmonary hypertension
• IV extravasation can cause tissue necrosis (central line preferred)

Uses in Critical Care

• Primary use: Hypotension and shock (especially distributive shock)
• Increases systemic vascular resistance, blood pressure, MAP (target MAP: 65)
• Sepsis and septic shock: First-line vasopressor per Surviving Sepsis Campaign guidelines
• Cardiogenic shock: Not indicated due to increased afterload

Conclusion

• Norepinephrine is a crucial medication in critical care
• Ensure proper dosing and monitoring to manage adverse effects
• First-line treatment for sepsis-induced hypotension post-fluid administration

Additional Resources

• YouTube: ICUAdvantage
• Patreon: For additional support and perks
• Links to nursing gear and t-shirt designs in the description

Stay tuned for upcoming lessons!