Vasopressors Emergency Medicine

What Are Vasopressors?

• Potent medications that constrict blood vessels → increase blood pressure.

• Goal: restore tissue perfusion in very hypotensive patients.

• Can also affect heart contractility and heart rate (inotropy).

• Commonly called “pressors.”

• Main inotrope used: Dobutamine (covered at end).

Receptor Sites

• Alpha receptors – vascular walls → vasoconstriction → ↑ BP.

• Beta-1 receptors – heart → ↑ contractility + ↑ heart rate.

• Beta-2 receptors – lungs → bronchodilation, vasodilation.

• V1 receptors – vascular walls → vasoconstriction → ↑ BP.

Key Vasopressors

1. Norepinephrine (Levofed)

• First-line agent: septic shock, neurogenic shock, cardiogenic shock, obstructive shock.

• Not for hypovolemic shock unless adequately volume resuscitated.

• Potent alpha activity, slight beta-1.

• Mixing: 4 mg in 250 mL NS (also 8 mg/250 or 16 mg/250).

• Onset: 1–2 min.

• Dose: 2–40 mcg/min (sometimes higher, e.g. up to 200). Start ~2 mcg/min.

• Titration: usually ↑ by 2 mcg every 3–5 min (per facility).

2. Vasopressin

• Pure V1 agonist.

• Never first-line, but added to norepinephrine in septic shock.

• Works well in acidotic environments.

• Onset: up to 15 min.

• Dose: 0.03 units/min (not titrated).

• Mixing: 20 units in 100 mL NS.

• Uses: septic shock add-on, diabetes insipidus, alternative to epinephrine in code situations.

3. Epinephrine

• Affects alpha, beta-1, beta-2.

• ↑ BP, ↑ HR, ↑ contractility, bronchodilation.

• Uses:

  • First-line in cardiac arrest.

  • Anaphylaxis and refractory shock.

  • Preferred when shock + low HR (no compensatory tachycardia).

• Onset: ~1 min.

• Concentration: 1 mg/250 mL or 4 mg/250 mL.

• Dose range: 0.5–2 mcg/kg/min (start ~0.1 mcg/kg/min).

• Complication: can ↑ lactate (important for lab interpretation).

4. Phenylephrine (Neo-Synephrine)

• Pure alpha agonist → ↑ SVR, ↑ BP.

• Add-on agent (after norepi, vasopressin, epi).

• Onset: 1 min.

• Concentration: 50 mg/250 mL NS.

• Dose range: 10–200 mcg/min (start ~100 mcg/min).

• Titration: 25 mcg every 3–5 min.

• Side effect: reflex bradycardia.

5. Dopamine

• Affects beta-1, alpha, dopamine receptors.

• Unpredictable effects → not commonly used in ER.

• Onset: 5 min.

• Concentration: 450 mg/250 mL NS.

• Dose: 2–20 mcg/kg/min.

  • <10 mcg/kg/min → beta-1 + renal perfusion.

  • 10 mcg/kg/min → alpha → vasoconstriction.

• Downsides: arrhythmias, less reliable vs norepi/epi.

6. Dobutamine

• Main inotrope (↑ contractility).

• Primarily beta-1 (contractility) + some beta-2 and alpha (vasodilation).

• May drop BP due to vasodilation.

• Uses: cardiogenic shock, heart failure (though controversial—“don’t whip a tired heart”). Sometimes add-on in septic shock.

• Onset: 10 min.

• Concentration: 500 mg/250 mL NS.

• Dose range: 2–20 mcg/kg/min (start at 2, titrate by 2 every 15 min).

Special Preparations

Dirty Epinephrine Drip

• 1 mg epi in 1 L NS.

• Run wide open → ~20–30 mcg/min.

• Use: critical, crashing patients (e.g., anaphylaxis, near-arrest).

• Buys time for pump infusion setup.

Norepinephrine Drip (self-mix in emergencies)

• 4 mg norepi in 250 mL NS.

• Label, shake, start infusion quickly.

Push-Dose Pressors

Phenylephrine Push-Dose

• Used for hypotension during RSI or sedation.

• Prep: 10 mg phenylephrine (1 mL) into 100 mL NS → 100 mcg/mL.

• Dose: 50–200 mcg (0.5–2 mL).

• Caution: do not use in bradycardic patients (can worsen).

Epinephrine Push-Dose

• Used in crashing/pre-arrest patients.

• Prep: Take flush (10 mL NS), remove 1 mL → 9 mL left. Add 1 mL from epi amp (1 mg/10 mL) → 100 mcg total = 10 mcg/mL.

• Dose: 10–20 mcg per push.

Complications of Vasopressors

• Extravasation → tissue necrosis.

• Arrhythmias.

• Ischemia to organs (heart, periphery, gut).

• Reflex bradycardia (phenylephrine).

• ↑ Lactate (epinephrine).

Clinicians Must-Knows

• Okay to start pressors peripherally in crashing patients (esp. norepi). Central line needed ASAP.

• Pressors are compatible with each other (verify per facility).

• Always have the next bag ready, never run dry.

• Know how to mix norepi, epi, and vasopressin yourself (don’t wait for pharmacy).

• Vasopressin: do not titrate, just start/stop.

• Label all lines (at pump + near patient).

• Do not bolus pressors → risk of acute hypertension, ischemia, arrhythmias.

• Allow time for onset before titrating further.

• Follow facility protocols + preceptor guidance.

• If starting a second pressor, advocate for arterial line placement.