| Drug Name | Receptor affected | HR | BP | CO | Cardiac Vasoconstriction | Peripheral Vasculature (B2) | Uses |
| Norepinephrine | α, β1 | ↔ | ↑↑↑ | ↔ or ↑ | ++++ | 0 | 2-40 ug/min cardiogenic shock |
| Epinephrine | α, β1, β2 | ↑↑↑ | ↑↑↑ | ↑↑↑ | ++++ | increased peripheral vasodilation | 1-20 ug/min cardiogenic shock and anaphylaxis epi activates everything) |
| Dopamine | α, β1, dopaminergic | ↑↑ | ↑ | ↑↑ | 0 | increased peripheral vasodilation and dopaminergic effects | 1-4 ug/kg/min or 4-20 ug/kg/min cardiogenic and neurogenic shock, if not tachy |
| Phenylephrine | α | ↔ or ↓ | ↑↑↑ | ↓ | +++ | 0 | 20-200 ug/min septic shock, can use if tachy |
| Vasopressin | vasopressin | – | ↑↑↑ | – or ↑ | ++++ | 0 | 0.01-0.03 ug/min septic shock |
| Isoproterenol | β1, β2 | ↑ | ↓ | ↑ | increased peripheral vasodilation | 0.05 – 0.2 mcg/kg/min heart block, bradydysrhythmias | |
| Dobutamine | β1, β2 (less β2 than isoproterenol | ↑ | ↓ | ↑ | 0 | increased peripheral vasodilation | 2-20 ug/kg/min cardiogenic and septic shock At high doses, causes headaches, paresthesias, and muscle cramps; Doesn’t work well if the patient on beta blocker, milrinone is similar choice |
| Milrinone | inotrope, vasodilation, PDE (phosphodiesterase inhibitor) | ↑↑ | – | ↑ | 0 | increased peripheral vasodilation | 0.375-0.75 ug/kg/min |
α = smooth muscle contraction resulting in increased systemic vascular resistance, thereby increasing afterload on the heart, which in turn increases blood pressure and decreases cardiac output.. Alpha1 adrenergic receptors are mainly present in the smooth muscles of the blood vessels and the muscle tissues of the heart.
β1 = positive chronography, dromotropic and ionotropic, increases heart rate and contractility. With these two increased values, the stroke volume and cardiac output will also increase. Beta-1 receptors are predominantly found in three locations: the heart, the kidney, and the fat cells.
β2 = smooth muscle relaxation, which may result in peripheral vasodilation with subsequent hypotension and reflex tachycardia. In cardiac cells, B2 receptor stimulation can cause Increased heart rate, increased heart muscle contraction, increased blood pressure. In skeletal muscle cells, stimulation of B2 receptors causes increased contractility and may lead to muscle tremors. Beta 2 receptors are predominantly present in airway smooth muscles. They also exist on cardiac muscles, uterine muscles, alveolar type II cells, mast cells, mucous glands, epithelial cells, vascular endothelium, eosinophils, lymphocytes, and skeletal muscles.
Remember:
- BP = SBP/DBP
- MAP = [SBP + (2 * DBP)]/3 (normal is 70-100)
- Map is largely based off of DBP because most of cardiac cycle is in diastole (filling)
- Cardiac Output (CO) = Sv + HR
Which pressor when:
- Septic shock: norepinephrine is first line, +/- vasopressin +/- dopamine
- Cardiogenic shock: dobutamine is first line, +/- IABP (intra-aortic balloon pump) +/- milrinone.
- Post-op: phenylephrine
- Post-code:epinephrine
I like these graphics, which came from Hollenberg SM. Vasoactive drugs in circulatory shock. Am J Respir Crit Care Med. 2011 Apr 1;183(7):847-55.
