Vasopressors increase vascular tone. Inotropes increase contractility. Inodilators increase contractility while reducing vascular resistance and may lower MAP. Pick by the hemodynamic problem (perfusion vs pump vs both), titrate to an individualized MAP target + perfusion (lactate, urine, mentation) — not a single number — and prefer a central line for prolonged/high-dose use.
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Receptor guide

what the drugs pull
ReceptorActionAgents
α₁Vasoconstriction (↑ SVR)norepi, phenylephrine, epi (high)
β₁Inotropy + chronotropy (↑ CO/HR)dobutamine, epi, dopamine, iso
β₂Vasodilation / bronchodilationepi, isoproterenol, dobutamine
V₁Vasoconstriction (non-adrenergic)vasopressin
PDE3 / AT₁Inodilation / vasoconstrictionmilrinone / angiotensin II
A

The agents at a glance

receptor · dose · effect · niche
AgentReceptorTypical doseEffect & niche
Norepinephrineα₁ > β₁0.01–0.5+ mcg/kg/min↑SVR, variable CO — first-line in septic shock and reasonable initial support in hypotensive cardiogenic shock
Epinephrineβ₁ β₂ > α₁0.01–0.5 mcg/kg/min↑CO ↑HR ↑SVR, ↑lactate — IM first for anaphylaxis. More refractory shock in small AMI-CS trial, not a universal mortality comparison
Phenylephrinepure α₁0.5–6 mcg/kg/min↑SVR, reflex ↓HR — selected vasodilatory hypotension or LVOT obstruction. May reduce CO
VasopressinV₁0.03 U/min (fixed)↑SVR, catecholamine-sparing — septic-shock add-on. Common fixed dose, but labeled regimens allow titration
DopamineD / β / α (dose)2–20 mcg/kg/minArrhythmogenic — generally avoid (SOAP-II), except selected bradycardia
Dobutamineβ₁ > β₂2–20 mcg/kg/min↑CO, ↓SVR (may ↓BP) — cardiogenic/low-output "cold" HF
MilrinonePDE3 inhib.0.125–0.75 mcg/kg/minInodilator ↑CO ↓SVR ↓PVR — RV failure/PH, β-blocked. Renal clearance, longer t½
Isoproterenolβ₁ β₂0.5–10 mcg/minChronotrope/inodilator — selected bradycardia or acquired, pause-dependent torsades. Avoid congenital long QT
Angiotensin IIAT₁Start 20 ng/kg/minVasodilatory shock. Max 80 ng/kg/min for first 3 h, then 40. Concurrent VTE prophylaxis
Doses are typical adult ICU ranges — verify current labeling, concentration, and pharmacy guidance. Several are weight-based. Vasopressin & isoproterenol are not.
B

Effect on the hemodynamic numbers

qualitative tendencies, not guaranteed responses
AgentMAPCOHRSVRPCWPHemodynamic signature
Norepinephrine↑↑↑/↔↔/↓↑↑↔CO depends on preload, afterload and ventricular function
Epinephrine↑↑↑↑↑↑↑↔↑ lactate via β₂ glycolysis (not always hypoperfusion)
Phenylephrine↑↓/↔↓↑↑↑reflex bradycardia, can ↓CO
Vasopressin↑↓/↔↓/↔↑↑variableMay decrease CO. Higher doses increase ischemic risk
Dopamine↑↑↑↑↑↑*↑arrhythmogenic. *α emerges at high dose
Dobutamine↔/↓↑↑↑↓↓inodilator — may drop BP → pair a pressor
Milrinone↓↑↑↔/↑↓↓↓↓↓ PVR too, renal clearance, long t½ (AKI)
Isoproterenol↓↑↑↑↑↑↓↓pure chronotrope/inodilator
Angiotensin II↑↑↔↔↑↑↔AT₁ vasoconstriction, catecholamine-sparing
C

Dosing, lines & monitoring

how to run them
  • Weight-based norepi/epi/phenyl/dopamine/dobutamine/milrinone (mcg/kg/min). Fixed vasopressin (0.03 U/min) & isoproterenol (mcg/min).
  • Onset / titration catecholamines act in seconds–minutes — titrate q2–5 min. Milrinone has a long t½ (no quick off).
  • Access central line for sustained / high-dose or concentrated mixes. Arterial line for true MAP.
  • Watch digital / mesenteric ischemia at high α-dose. Reduce milrinone in AKI.
Match the agent to the shock physiology: a vasodilated patient needs a vasopressor. A failing pump needs an inotrope. Use both when low output and hypotension coexist. Reassess rhythm, filling, afterload and reversible causes before escalating.
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Pick the agent by the hemodynamic problem

phenotype → drug

Low vascular tone

Norepinephrine for septic shock.

Add vasopressin, then epinephrine if MAP remains low.

Low output

Correct rhythm, filling and cause. Consider dobutamine or milrinone.

If hypotensive, support MAP with norepinephrine. Reassess output and perfusion.

Mixed low output + low tone

Pressor for vascular pressure plus inotrope for persistent low output.

Escalating requirements warrant repeat echo/hemodynamics and timely support-team review.

Qualitative decision map. Shock can occur without MAP below 65. A pressure response alone does not establish adequate perfusion.

A

Choose by shock type

first → next
ShockSequence
CardiogenicNorepinephrine if hypotensive. Add dobutamine/milrinone for persistent low-output hypoperfusion. Consider tMCS if refractory
Septic / distributiveNorepinephrine → add vasopressin → epinephrine if MAP remains low. With cardiac dysfunction, SSC 2026 suggests norepinephrine or epinephrine initially. For persistent hypoperfusion after adequate volume/BP, add dobutamine to norepinephrine or use epinephrine alone.
RV failureNorepi/vasopressin for MAP (coronary perfusion) + milrinone/dobutamine, iNO/pulmonary vasodilator. Avoid hypoxia/hypercarbia
AnaphylacticEpinephrine (IM → infusion), fluids, adjuncts
Hypovolemic / hemorrhagicVolume / blood first — pressors only as a bridge
BradycardicAtropine if appropriate → pacing and/or epi/dopamine. Do not delay pacing for unstable high-grade block
B

Run them safely

access · targets · weaning
  • Access Do not delay a needed pressor for central access. Use a monitored peripheral IV, inspect the site and have an extravasation rescue plan.
  • Targets Sepsis: initial MAP 65 mm Hg. SSC 2026 suggests 60–65 at age ≥65. Individualize to perfusion, not hypertension history alone.
  • Refractory shock Confirm phenotype and source control. Treat hypoxemia, severe metabolic disturbance and an identified endocrine emergency.
  • Wean Taper according to adverse effects and perfusion response. No universally proven withdrawal sequence.
C

Inopressor pearls

the gotchas
  • Milrinone renal clearance → accumulates in AKI. Vasodilates → can drop BP (may need a pressor alongside).
  • Dobutamine tachycardia/arrhythmia, tachyphylaxis, ↓SVR.
  • Epinephrine ↑ lactate via β₂ glycolysis — not always hypoperfusion.
  • Phenylephrine reflex bradycardia and increased afterload can worsen a low-output state.
D

Refractory shock — adjuncts

beyond the drips
  • Steroids SSC 2026 suggests IV corticosteroids for septic shock. A typical regimen is hydrocortisone 200 mg/day, divided or infused.
  • Vasoplegia Methylene blue is off label, with uncertain survival benefit. Avoid in G6PD deficiency and review serotonergic drug interactions.
  • Fix the substrate Treat the cause of acidosis and hypoxia. Replace calcium for a defined indication, not routinely for all shock.
  • Cardiogenic & escalating → temporary MCS (→ Shock / VA-ECMO cards).
The one-liner: norepinephrine is the default vasopressor. Add an inotrope (dobutamine/milrinone) when the pump is the problem. Layer vasopressin → epinephrine for refractory vasodilatory shock. Titrate to perfusion, secure access, and treat the cause. Hemodynamic assessment