Source / episode info

• **Episode:**333
• **Title:**Divine Intervention Episode 333 – The Clutch Pressor and Inotrope Podcast for Step 2CK/3.
• **Published:**2021-08-16
• Source:Episode page

One-liner

This episode provides a comprehensive review of positive inotropes (dobutamine, milrinone) and vasopressors (norepinephrine, phenylephrine, vasopressin), detailing their mechanisms of action, clinical uses in septic shock and cardiac stress testing, and covering high-yield topics like digoxin toxicity and the role of desmopressin.

High-yield summary

• Digoxin Toxicity: Inhibition of the {Na}^+/{K}^+ ATPase pump leads to increased intracellular calcium ({Ca}^{2+}) in myocardial cells, causing positive inotropy and arrhythmias. Treatment is specific: Anti-digoxin Fab fragments.
• Milrinone (PDE III Inhibitor): Increases cardiac contractility by increasing cAMP while simultaneously causing systemic vasodilation (decreasing afterload). This results in a widened pulse pressure (increased systolic BP, decreased diastolic BP).
• Septic Shock Management: The stepwise approach is crucial: First line -> Norepinephrine (_1 and _1 effects); Second line -> Vasopressin; Third line -> Epinephrine.
• Dobutamine ( _1 Agonist): Used for chemical stress testing in non-exercising patients and in cardiogenic shock. It stimulates _1 receptors in the heart and kidney, leading to increased cardiac output and RAAS activation ( {Ang II}, {Aldosterone}).
• Vasopressin/Desmopressin: Used for SIADH management (free water retention) and treating bleeding disorders by stimulating the release of von Willebrand factor (vWF) from the vildopodial body.
• Phenylephrine: A pure _1 agonist that causes peripheral vasoconstriction, increasing systemic vascular resistance and blood pressure; be aware of potential reflex bradycardia.

Learning objectives

• Differentiate the mechanisms and clinical uses of positive inotropes (e.g., dobutamine, milrinone) versus vasopressors (\alpha_1 agonists).
• Recognize the specific sequence of pressor agents required for managing septic shock.
• Understand the pathophysiology of digoxin toxicity and its antidote.
• Identify the indications for desmopressin in both SIADH and bleeding disorders (vWBD).
• Predict hemodynamic changes resulting from \beta_1 agonism or pure \alpha_1 agonism.