The Critical Care Medic's Guide to Vasopressors
Understanding Epinephrine, Norepinephrine, Vasopressin, Dopamine, Dobutamine & More
"Treat the physiology—not just the blood pressure."
One of the biggest transitions from traditional EMS into critical care medicine isn't learning new medications—it's learning why you're choosing one vasoactive medication over another.
Two patients can both have a MAP of 52 mmHg.
One needs norepinephrine.
Another needs epinephrine.
Another needs dobutamine.
Another needs blood.
Another simply needs fluids.
If you choose the wrong medication, you may improve the blood pressure while making the patient's underlying physiology worse.
The monitor won't tell you which pressor to use.
Understanding shock physiology will.
Let's dive in.
Before You Hang a Pressor
Before reaching for a syringe or infusion pump, ask yourself one simple question:
Why is this patient hypotensive?
Blood pressure is simply the symptom.
Shock is the disease.
There are four major categories of shock every critical care provider should recognize:
Hypovolemic Shock
The tank is empty.
Examples include:
-
Hemorrhage
-
Dehydration
-
GI losses
-
Burns
The answer usually isn't a pressor.
It's replacing volume.
Cardiogenic Shock
The pump is failing.
Examples include:
-
Acute myocardial infarction
-
Severe heart failure
-
Cardiomyopathy
-
Mechanical complications
Increasing vascular resistance without improving cardiac output can actually worsen perfusion.
Distributive Shock
The pipes are too large.
Examples include:
-
Septic shock
-
Neurogenic shock
-
Anaphylaxis
This is where vasopressors truly shine.
Obstructive Shock
Something is physically blocking circulation.
Examples include:
-
Massive pulmonary embolism
-
Cardiac tamponade
-
Tension pneumothorax
No amount of Levophed will fix a tension pneumothorax.
You must correct the obstruction.
Stop Chasing Blood Pressure
One of the biggest mistakes in EMS is focusing on systolic blood pressure alone.
A patient doesn't care if their systolic pressure is 120.
Their kidneys don't.
Their brain doesn't.
Their heart doesn't.
What they care about is perfusion.
That's why critical care focuses on:
Mean Arterial Pressure (MAP)
For most critically ill adults, our goal is:
MAP ≥65 mmHg
But remember...
A MAP of 65 means nothing if the patient still has poor perfusion.
Always evaluate:
-
Mental status
-
Skin signs
-
Capillary refill
-
Urine output
-
ETCO₂ trends
-
Lactate
-
Pulse pressure
Numbers never replace your patient assessment.
Norepinephrine (Levophed)
"The King of Septic Shock"
If you've spent any time in an ICU or flight program, you've probably heard the phrase:
"Levophed first."
There's a reason.
Primary Receptors
★★★★☆ Alpha-1
★★☆☆☆ Beta-1
Very little Beta-2 activity.
What It Does
Think of Levophed as tightening the vascular system.
It increases systemic vascular resistance by constricting arteries throughout the body.
The result is:
-
Increased MAP
-
Improved coronary perfusion
-
Improved cerebral perfusion
-
Minimal increase in heart rate compared to epinephrine
Unlike epinephrine, Levophed doesn't dramatically increase myocardial oxygen demand.
That's a huge advantage in critically ill patients.
Best Uses
Septic Shock
This is the gold standard.
Sepsis causes profound vasodilation.
Levophed restores vascular tone.
Neurogenic Shock
Loss of sympathetic tone causes massive vasodilation.
Again...
Levophed restores vascular resistance.
Vasodilatory Shock
Whether from medications, anesthesia, or other causes, Levophed excels when the primary problem is low systemic vascular resistance.
Cardiogenic Shock With Severe Hypotension
Many clinicians now prefer norepinephrine over epinephrine because it generally causes fewer arrhythmias and less tachycardia while maintaining perfusion pressure.
Downsides
No medication is perfect.
Levophed can cause:
-
Peripheral ischemia
-
Digital ischemia
-
Extravasation injury
-
Excessive vasoconstriction at high doses
Always monitor extremities carefully.
Practical EMS Tips
✔ Don't chase "normal" blood pressures.
✔ Titrate to perfusion.
✔ Watch pulse pressure.
✔ Follow ETCO₂ trends.
✔ Reassess skin temperature and mental status frequently.
Epinephrine
The Swiss Army Knife
If Levophed is the king...
Epinephrine is the multitool.
It affects nearly every major adrenergic receptor.
Primary Receptors
★★★★★ Beta-1
★★★★☆ Beta-2
★★★★☆ Alpha-1
Its effects change depending on the dose.
Lower doses produce more beta effects.
Higher doses become increasingly alpha dominant.
What Epinephrine Does
Epinephrine:
-
Increases heart rate
-
Increases contractility
-
Increases cardiac output
-
Raises systemic vascular resistance
-
Causes bronchodilation
-
Raises blood glucose
-
Raises serum lactate
It truly does a little bit of everything.
Best Uses
Cardiac Arrest
No surprise here.
Anaphylaxis
The perfect medication.
It simultaneously treats:
-
Bronchospasm
-
Vasodilation
-
Airway edema
-
Hypotension
No other medication accomplishes all of these.
Bradycardia with Hypotension
When your patient is both slow and hypotensive, epinephrine often makes far more physiologic sense than Levophed.
Severe Cardiogenic Shock
Patients with profound pump failure may benefit from epinephrine's powerful inotropic effects.
Downsides
The downside to epinephrine is that it works...
Almost too well.
Expect:
-
Tachycardia
-
Increased myocardial oxygen demand
-
Increased dysrhythmias
-
Elevated lactate levels
-
Higher myocardial workload
Remember:
A rising lactate after starting epinephrine doesn't always mean worsening shock.
Sometimes it's simply the medication.
Practical EMS Tips
If the patient is:
Hypotensive...
Bradycardic...
Cold...
Poorly perfusing...
Think epinephrine.
Vasopressin
The Forgotten Hormone
Unlike catecholamines...
Vasopressin doesn't work through alpha or beta receptors.
Instead, it works on:
V1 Receptors
Completely different pathway.
That's what makes it so valuable.
During prolonged septic shock, patients frequently become relatively vasopressin deficient.
Giving vasopressin restores vascular tone through a mechanism completely independent of catecholamines.
Best Uses
-
Refractory septic shock
-
High norepinephrine requirements
-
Catecholamine sparing
Why We Love It
Vasopressin:
-
Doesn't increase heart rate
-
Doesn't increase myocardial oxygen demand
-
Works when catecholamines begin losing effectiveness
-
Allows lower doses of norepinephrine
Think of it as backup power for the vascular system.
Downsides
Watch for:
-
Digital ischemia
-
Mesenteric ischemia
-
Reduced peripheral perfusion
Most protocols use a fixed dose instead of titrating.
Dopamine
Yesterday's Favorite
Years ago...
Everyone received dopamine.
Today?
Not so much.
Why It Fell Out of Favor
Compared to norepinephrine, dopamine causes:
-
More tachycardia
-
More arrhythmias
-
Higher myocardial oxygen consumption
-
Less predictable outcomes
Evidence gradually pushed critical care toward Levophed.
Does Dopamine Still Have a Role?
Occasionally.
If a profoundly hypotensive patient is also severely bradycardic—and epinephrine isn't available—dopamine may still be useful.
Outside of that...
Most critical care systems rarely reach for it first.
Phenylephrine
Pure Alpha
Phenylephrine is almost exclusively an alpha agonist.
That means:
No increase in contractility.
Minimal increase in heart rate.
Just vasoconstriction.
Think of it as simply tightening the pipes.
Best Uses
Patients who already have significant tachycardia.
Anesthesia-induced hypotension.
Certain atrial fibrillation patients.
It's much less common in prehospital critical care but still worth understanding.
Dobutamine
Not a Pressor...
An Inotrope
This distinction is important.
Dobutamine primarily improves:
-
Contractility
-
Stroke volume
-
Cardiac output
It is not designed to raise systemic vascular resistance.
Best Uses
Cold cardiogenic shock.
Severe heart failure.
Low cardiac output with adequate blood pressure.
Sometimes patients don't need tighter arteries.
They simply need a stronger pump.
Angiotensin II
The newest player.
Rarely carried in EMS.
Primarily used in ICUs for refractory vasodilatory shock.
As research continues, don't be surprised if this medication becomes more common over the next decade.
Push-Dose Pressors
Every critical care provider should understand push-dose pressors.
These include:
-
Push-dose epinephrine
-
Push-dose phenylephrine
They're bridge therapies.
They buy you time.
They do not replace continuous infusions.
Think of them as a temporary solution while preparing definitive treatment.
Choosing the Right Pressor
Septic Shock
Fluid resuscitation
↓
Norepinephrine
↓
Add Vasopressin if escalating doses are needed
↓
Consider Epinephrine for refractory shock
Cardiogenic Shock
Hypotensive?
↓
Norepinephrine
Poor cardiac output?
↓
Consider Dobutamine
Persistent shock?
↓
Mechanical circulatory support when available
Bradycardia + Hypotension
↓
Epinephrine
↓
Dopamine if epinephrine isn't available
Neurogenic Shock
↓
Norepinephrine
Anaphylaxis
↓
Epinephrine
Always.
Common Mistakes
❌ Treating the blood pressure instead of the patient.
❌ Forgetting to identify the underlying type of shock.
❌ Escalating Levophed endlessly without considering vasopressin.
❌ Using dopamine because "that's what we've always done."
❌ Waiting too long to initiate vasopressors.
❌ Forgetting that fluids, blood, or source control may be the actual treatment.
Current Trends in Critical Care
Modern critical care transport teams are shifting toward:
-
Earlier recognition of shock.
-
Earlier norepinephrine initiation.
-
Less dopamine use.
-
More physiology-based medicine.
-
Earlier vasopressin in refractory septic shock.
-
Greater focus on perfusion markers rather than blood pressure alone.
The trend is simple:
Treat the cause.
Not the number.
Final Thoughts
Great critical care medics don't memorize medication cards.
They understand physiology.
Levophed isn't "better" than epinephrine.
Epinephrine isn't "stronger" than vasopressin.
Dobutamine isn't "just another pressor."
Each medication exists for a different reason.
The best critical care providers ask one question before hanging any vasoactive medication:
"What physiology am I trying to fix?"
Once you answer that question, choosing the right medication becomes much easier.
Stop chasing blood pressure.
Start chasing perfusion.
Your patients will thank you for it.