MICU intern's survival guide vasopressors
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Norepinephrine
Mechanism of action
Acts on both alpha1 (vasoconstriction of blood vessels) and beta1 receptors (increases cardiac output).
Indications
- Septic shock
- Cardiogenic shock - Recent studies have shown that norepinephrine may be better than dopamine in cardiogenic shock due to a decreased risk of tachyarrhythmias.
- In cases where the type of shock is unclear, norepinephrine can be tried as a first line agent.
Doses
- 1-30 mcg/min.
Dopamine
Mechanism of action
- Acts on alpha1 (vasoconstriction of blood vessels), beta1 (increases cardiac output) and dopamine receptors (scattered throughout the body).
- Its action is dose dependent. At low doses it predominantly acts on cardiac receptors (1-10 mcg/min) with less vasoconstriction activities. At higher doses it has both vasoconstriction and cardiac activities.
Indications
- Cardiogenic shock
- Septic shock - second line treatment for septic shock
Side-effects
- Arrhythmogenic. Avoid in patients prone to arrhythmias.
- Doses
- 1-20 mcg/min.
Dobutamine
Vasopressin
Mechanism of action
- Acts by stimulating V1 (vasopressin) receptors in vascular and GI smooth muscles causing contraction. It also has anti-diuretics effect.
Indications
- Septic shock - second line treatment for septic shock
Side-effects
- Coronary and splanchnic vasoconstriction. Avoid in NSTEMI (can use in mild troponin leaks but avoid if Trops high 5-10) and gut ischemia.
Doses
- .03units/min (only vasopressor which is not titrated).
Phenylephrine
Mechanism of action
- Acts only on alpha1 receptors (vasoconstriction). No action on cardiac receptors and is cardiac neutral.
Indications
- Used in neurogenic shock
- Third or fourth line vasopressor in septic shock (refractory to norepinephrine, dopamine, and vasopressin).
Side-effects
- Can cause reflex bradycardia but not tachycardia.