Vasopressors: Medications That Increase Blood Pressure Through Vasoconstriction
Vasopressors are medications that increase blood pressure primarily through vasoconstriction and include: norepinephrine, epinephrine, dopamine, phenylephrine, vasopressin, and angiotensin II. 1
Primary Vasopressors
Pure Vasoconstrictors
- Phenylephrine: Acts solely through alpha-1 adrenergic receptor stimulation causing vasoconstriction without cardiac effects 2
- Vasopressin: Non-adrenergic peripheral vasoconstrictor that acts on AVPR1a receptors, causing coronary and renal vasoconstriction 3, 4
- Angiotensin II: Acts on angiotensin receptors (AG1, AG2) to cause vasoconstriction 4
Inoconstrictors (Combined Vasopressor + Inotropic Effects)
- Norepinephrine: Primarily alpha-1 and alpha-2 adrenergic effects with mild beta-1 activity, providing reliable vasoconstriction with minimal heart rate impact and mild positive inotropy 5, 2
- Epinephrine: Mixed alpha and beta adrenergic effects, causing both vasoconstriction and significant cardiac stimulation 2
- Dopamine: Dose-dependent effects on dopaminergic, beta, and alpha receptors 2
Clinical Hierarchy and Recommendations
Norepinephrine is the first-line vasopressor for distributive shock (particularly septic shock) after adequate fluid resuscitation 1, 6. This recommendation is based on evidence showing norepinephrine reduces mortality compared to dopamine (absolute risk reduction of 11%, number needed to treat of 9) with fewer adverse events including cardiac arrhythmias 6.
Second-Line Agents
When hypotension persists despite norepinephrine:
- Vasopressin (up to 0.03 units/min) can be added to reduce norepinephrine requirements 1
- Epinephrine may be added or used as a single agent, particularly when myocardial depression is present 1
- Angiotensin II may be useful for rapid resuscitation in profoundly hypotensive patients 4
Context-Specific Choices
- Cardiogenic shock with bradycardia: Dopamine may be considered 1
- Afterload-dependent states (aortic stenosis, mitral stenosis): Phenylephrine or vasopressin 1
- Cardiac arrest: Epinephrine remains the standard vasopressor; vasopressin offers no advantage as a substitute 3
Important Caveats
Dopamine has fallen to almost no-use recommendation due to increased arrhythmic events and higher mortality signals compared to norepinephrine, and should only be used in hypotensive patients with bradycardia or low risk for tachycardia 1, 4.
Phenylephrine should be reserved for salvage therapy in distributive shock due to lack of comparative mortality data and potential for excessive vasoconstriction without inotropic support 1.
The evidence consistently shows no definitive survival benefit for any specific vasopressor choice in randomized controlled trials, with the notable exception of norepinephrine's superiority over dopamine 1, 4. Therefore, recommendations are based primarily on organ dysfunction effects and safety profiles rather than mortality benefits 1.