Vasopressors (Part 1) - ICU Drips

Summary

This ICU Advantage video lesson focuses on vasopressors, crucial medications in critical care that increase blood pressure by activating adrenergic receptors, leading to vasoconstriction. The video explains vasopressors' impact on SVR and cardiac output, discusses receptor types, and covers various vasopressors including Levophed, Neosynephrine, Vasopressin, Epinephrine, Dopamine, and Giapreza. It provides insights into their specific actions, receptor activations, and appropriate dosages, emphasizing the importance of understanding these to manage hypotensive and shock patients effectively.

Takeaways

• 💡 Vasopressors, also known as 'pressors', are critical care medications primarily used to increase systemic vascular resistance (SVR) and blood pressure in hypotensive and shock patients.
• 🔍 These medications work by activating adrenergic receptors, leading to peripheral vasoconstriction and improved tissue perfusion, especially in end organs.
• 📌 Normal SVR ranges from 600-1200 dynes/s/cm-5, and vasopressors aim to increase this value to enhance vascular constriction.
• 🚑 The primary goal of vasopressors is to increase SVR, but they can also affect cardiac output through changes in heart rate, contractility, and preload.
• 🔬 Understanding adrenergic receptors, particularly alpha-1, beta-1, and beta-2, is crucial for grasping how vasopressors function and their potential effects on the body.
• 💊 Levophed (norepinephrine) is often the first-line pressor due to its strong alpha-1 agonist effects and is listed as the primary pressor in surviving sepsis campaign guidelines.
• 🌡 Neosynephrine (phenylephrine) is a pure alpha receptor agonist that can cause bradycardia due to baroreceptor-mediated reflex and is used as an alternative or adjunct in therapy.
• 🌊 Vasopressin is a second-line treatment for catecholamine-resistant shock, acting as a v1 receptor agonist to increase blood pressure without alpha or beta receptor activation.
• ⚠️ Epinephrine is a non-selective adrenergic agonist used as a last resort in shock treatment, affecting all adrenergic receptors with a preference for alpha receptors at higher doses.
• 📈 Dopamine's effects are dose-dependent, acting as a beta agonist at lower doses and an alpha agonist at higher doses, impacting SVR, heart rate, and contractility.
• 🆕 Giapreza (Angiotensin-2) is a newer pressor that activates the renin-angiotensin-aldosterone system, causing arterial vasoconstriction primarily through AT2 receptor activation.

Q & A

What are vasopressors and why are they important in critical care?

Vasopressors, also known as 'pressors', are a subset of vasoactive medications used in critical care to increase blood pressure by activating adrenergic receptors, leading to peripheral vasoconstriction. They are crucial for managing hypotension and shock, aiming to improve systemic vascular resistance (SVR) and ultimately tissue perfusion, especially in end organs.

What is the normal range for systemic vascular resistance (SVR)?

The normal SVR range is between 600-1200 dynes/s/cm-5. SVR measures afterload, which is essentially how constricted a patient's blood vessels are.

How do vasopressors impact cardiac output?

Vasopressors primarily work to increase afterload by raising SVR, which can help increase blood pressure. Some vasopressors can also affect heart rate and contractility, which are components of cardiac output, potentially providing additional benefits or challenges in patient management.

What are the alpha and beta adrenergic receptors, and why are they significant for vasopressors?

Alpha receptors (specifically alpha-1) are significant for vasopressors because they are responsible for smooth muscle contraction, leading to vasoconstriction. Beta receptors (beta-1 and beta-2) are also important; beta-1 receptors, located in the heart, affect heart rate and contractility, while beta-2 receptors, found in the lungs, can cause smooth muscle relaxation.

What is the difference between an agonist and an antagonist in the context of vasopressors?

An agonist is a substance that activates a receptor, whereas an antagonist does not activate the receptor and can block the effects of agonists. Vasopressors are agonists for various receptors, including alpha-1, beta-1, and others, which they activate to increase blood pressure.

What is Levophed, and why is it typically the first-line pressor used?

Levophanine, also known as norepinephrine or 'levo', is a direct-acting vasopressor that is typically the first-line pressor used due to its strong alpha-1 receptor agonist effects and some beta-1 agonist effects. It is recommended as the primary pressor in surviving sepsis campaign guidelines.

What is Neosynephrine, and how does it differ from Levophed?

Neosynephrine, also known as phenylephrine or 'neo', is a pure alpha receptor agonist, unlike Levophed which also has beta-1 agonist effects. Neosynephrine is a direct-acting vasopressor that can cause baroreceptor-mediated reflex bradycardia due to its pure alpha effects, and is often used as an alternative or adjunct in cases of Levophed-induced arrhythmias.

How does Vasopressin work, and in what situations is it typically used?

Vasopressin works by acting as a v1 receptor site agonist, causing smooth muscle contraction and increasing blood pressure. It is often used as a second-line treatment for patients who are resistant to catecholamine vasopressors.

What is the role of Epinephrine in treating shock, and how does its action differ from other vasopressors?

Epinephrine is a non-selective agonist of all adrenergic receptors and is typically used as a last resort in shock treatment when other measures fail. It increases blood pressure and can significantly impact heart rate and contractility due to its effects on beta-1 and beta-2 receptors.

How does dopamine function as a vasopressor, and what is its dose-dependent effect?

Dopamine acts as a vasopressor in a dose-dependent manner, with low doses (0.5 to 2 mcg/kg/min) having renal effects, medium doses (5 to 10 mcg/kg/min) acting as a beta agonist with inotropic effects, and higher doses (10 to 20 mcg/kg/min) acting more as an alpha agonist, increasing SVR.

What is Giapreza, and how does it differ from other vasopressors?

Giapreza, or Angiotensin-2 in IV form, is a synthetic peptide that activates the renin-angiotensin-aldosterone system (RAAS) by agonizing AT2 receptors, causing arterial vasoconstriction. Unlike other vasopressors, it does not affect alpha or beta receptors and has no impact on heart rate or contractility.