<aside> ⚡

Clinical pearls:

• In shock + pulmonary hypertension, use:
  • Epinephrine for hypotensive cold shock
  • Milrinone or Dobutamine for RV failure or PH, but only if BP is stable
• Avoid vasodilators like milrinone or dobutamine in initial hypotensive states → these agents will lower SVR too much
• Epinephrine is preferred in decompensated shock with acidosis
• Consider transitioning to milrinone or dobutamine once BP stabilizes if pulmonary pressures remain high </aside>

low β1 > β2 > ⍺1 high ⍺1 > β1 > β2** | β1: ↑ heart rate, ↑ contractility α1: vasoconstriction (↑ SVR, ↑ BP) β2: mild vasodilation | ↑↑ | ↑↑ | ↑ | ↑↑ | - Cold shock w/ hypotension and metabolic acidosis

• Cardiac arrest, anaphylaxis, post-arrest support | Infusion: 0.05–3 mcg/kg/min Bolus: 0.01 mg/kg IV in resuscitation | Effective even in acidotic states | | **Norepinephrine

⍺1 > β1 > β2** | Potent α1 → vasoconstriction Some β1 → ↑ contractility | ↑ | ↑ | ↑↑ | ↑↑ | Warm shock, distributive shock | 0.05–1.5 mcg/kg/min  IV infusion | ↑ SVR in hypotensive states | | **Phenylephrine

Pure ⍺1** | α1 → vasoconstriction | ↔︎/↓ (reflex mediated) | ↔︎/ mild ↓ | ↑↑ | ↑↑ | Vasodilatory shock with tachycardia or when β-stimulation is not desired | 0.05-1.5 mcg/kg/min | | | **Isoproterenol

β1 = β2** | Pure β1 + β2 agonist → ↑ HR and contractility, vasodilation | ↑↑ | ↑ | ↓ | ↓ | Bradycardia, heart block | 0.05–0.5 mcg/kg/min | Not used in shock due to vasodilation-induced hypotension | | **Dopamine

low D1 > β1 > ⍺1 high ⍺1 > β1 > D1** | Dose dependent Low (1–5 mcg/kg/min): renal vasodilation (D1) – not reliable Moderate (5–10): β1 → ↑ HR, ↑ contractility High (>10): α1 → ↑ vasoconstriction | ↑ | ↑ | ↑ (dose-dependent) | ↑ | Mild-to-moderate shock, bradycardia, or renal hypoperfusion | 3–20 mcg/kg/min IV infusion | | | **Dobutamine

β1 > β2** | Strong β1, mild β2 → ↑ contractility, slight vasodilation

• Little α1 activity | ↑ | ↑↑ | ↓ | ↔︎ / ↓ | - Low CO with stable BP
• Myocarditis, cardiomyopathy
• Post-op support | 2–20 mcg/kg/min IV infusion | Avoid in significant hypotension due to **vasodilatory effect
• Preferred in pHTN** | | **Milrinone

PDE-3 inhibitor** | ↑ cAMP → inotropy + lusitropy (relaxation) Vasodilation (↓ SVR, ↓ PVR) | ↔︎ | ↑↑ | ↓↓ | ↓ | - Heart failure with preserved BP

• Post-op | Loading: 50 mcg/kg over 30–60 min (optional) Maintenance:  0.25–0.75 mcg/kg/min | Excellent for afterload reduction and diastolic dysfunction - Preferred in pHTN |

• Autonomic Receptors & Related Pharmacology (Adrenergic, Cholinergic) ★