Rapid Review·Cardiovascular
Select any text to highlight it or add a note.
PHARMACOLOGY
T3Take a glanceVasopressors & Inotropes
Focus on
Pressure and squeeze support in shock, and which agent belongs to which shock.
Key takeaways
The pressors
Norepinephrine (alpha-1 far more than beta-1)
FIRST-LINE for septic and distributive shock. A potent vasoconstrictor with modest inotropy, which is what a vasodilated patient needs.Epinephrine (beta-1 and beta-2 at low dose, alpha-1 at high dose)
anaphylaxis and cardiac arrest, and second-line in septic shock.Phenylephrine (pure alpha-1)
raises systemic vascular resistance with reflex bradycardia, which makes it useful when a tachyarrhythmia limits the other agents.Vasopressin (V1 receptors)
a catecholamine-sparing adjunct in refractory septic shock, producing vasoconstriction independent of the adrenergic system.Dopamine (dose-dependent: low is D1 renal, mid is beta-1, high is alpha-1)
largely out of favour, because it causes more arrhythmias than norepinephrine.The inotropes
Dobutamine (beta-1 far more than beta-2)
the INOTROPE of choice for cardiogenic shock and decompensated heart failure. It raises contractility with mild vasodilation, which drops afterload and can therefore lower blood pressure.Milrinone (PDE-3 inhibitor)
an "inodilator". Raising cAMP does two things: in the cardiomyocyte it raises calcium influx and contractility; in vascular smooth muscle it inhibits MLCK and dilates the vessel, lowering preload and afterload. Useful in acute decompensated heart failure with cardiogenic shock, including patients on beta-blockers, because it bypasses the beta receptor entirely. Adverse: tachycardia, ventricular arrhythmias, hypotension.| Agent | Receptors | First choice for | Note |
|---|---|---|---|
| Norepinephrine | Alpha-1 >> beta-1 | Septic / distributive shock | Potent vasoconstrictor, modest inotropy |
| Epinephrine | Beta at low dose, alpha at high dose | Anaphylaxis, cardiac arrest | Second-line in sepsis |
| Phenylephrine | Pure alpha-1 | When tachyarrhythmia limits other agents | Causes reflex bradycardia |
| Vasopressin | V1 | Refractory septic shock | Catecholamine-sparing adjunct |
| Dopamine | Dose-dependent D1, beta-1, alpha-1 | Rarely used now | More arrhythmias than norepinephrine |
| Dobutamine | Beta-1 >> beta-2 | Cardiogenic shock, decompensated HF | Raises contractility, can lower BP |
| Milrinone | PDE-3 inhibition | Acute decompensated HF | Works despite beta-blockade |
A beta-blocked patient is in acute decompensated heart failure and dobutamine is not working. Which inotrope, and why?
Milrinone: it raises cAMP by blocking PDE-3, downstream of the blocked beta receptor.
How it's tested
Norepinephrine is the first-line vasopressor for septic shock, because the problem there is pathological vasodilation and norepinephrine is the strongest vasoconstrictor with acceptable inotropy. Dobutamine is the inotrope of choice for cardiogenic shock, since it raises contractility while modestly lowering afterload, and the catch worth remembering is that this can drop the blood pressure. Milrinone is the answer when a patient is already beta-blocked, because it acts downstream of the receptor.
Go deeper
First Aid 2026 — CV/Pharmacology (sympathomimetics in shock) · B&B — Vasopressors & inotropes · Mehlman — HY Cardio (shock hemodynamics and agents); pairs with the Shock & Cardiac Tamponade page
You just read one page of 944
The rest of Step 1, written exactly like this.
Rapid Review is the reading layer of a full Step 1 platform: a schedule fitted to your exam date, flashcards for every page, and a mentor a message away.
Every Step 1 system
Written the same way: what to know, how it’s tested, where to go deeper.
A plan built to your exam date
Tell us when you sit, and the schedule fits the whole library and your question bank to it.
Flashcards for every page
Ready-made spaced-repetition decks linked to each topic, so nothing you read gets forgotten.
