Vasopressors: When To Start Them And Dosages
Pressors don't have to scare you anymore...
Figuring out when to start vasopressors in the ER can feel overwhelming. Between multiple clinical scenarios and several different pressor options, choosing the right agent isn’t always straightforward.
The goal of this article is to simplify when to initiate pressors and which ones to consider based on the clinical situation.
Below is a quick sheet for reference followed by some greater details for those who like to read!
SEPTIC SHOCK
| Medication | Dose | When to Use | Key Notes |
|---|---|---|---|
| Norepinephrine (1st-line) | 0.05 mcg/kg/min | Persistent hypotension after 30 mL/kg fluids | Strong α1 → vasoconstriction; mild β1 |
| Epinephrine | 0.01–0.05 mcg/kg/min | Add if MAP still low OR need inotropy | ↑ HR, ↑ contractility; can ↑ lactate |
| Vasopressin | 0.01–0.04 units/min | Adjunct to NE in refractory shock | Non-adrenergic; restores vascular tone |
| Goal MAP | ≥ 65 | — | Titrate to perfusion |
***IN ACIDOTIC STATES CONSIDER STARTING/ ADDING VASOPRESSIN EARLY BECAUSE ACTS ON V1 AND V2 RECEPTORS
*Norepinephrine and Epi require higher doses below pH of 7.1/ doesn't work as well!
HYPOVOLEMIC SHOCK
| Medication | Dose | When to Use | Key Notes |
|---|---|---|---|
| Norepinephrine | 0.01–0.05 mcg/kg/min (max 0.5) | Hypotension despite fluids | Use small titrations; improves vascular tone |
| Goal MAP | ≥ 65 | — | Must give fluids first |
CARDIOGENIC SHOCK
| Medication | Dose | When to Use | Key Notes |
|---|---|---|---|
| Norepinephrine | 0.01–0.03 mcg/kg/min (max 0.5) | Hypotension + low perfusion | Mild β1 → supports MAP without ↑ HR too much |
| Dobutamine | 2–5 mcg/kg/min | Low cardiac output with preserved SVR | Strong inotrope; may ↓ BP |
| Milrinone | 0.125–0.5 mcg/kg/min | Pulmonary HTN or dobutamine failure | Vasodilatory; can worsen hypotension |
| Combo: NE + Dobutamine | See above | Low MAP + low CO | NE = afterload; Dobutamine = inotropy |
NEUROGENIC SHOCK
| Medication | Dose | When to Use | Key Notes |
|---|---|---|---|
| Norepinephrine (1st-line) | 0.01–0.1 mcg/kg/min | Hypotension + bradycardia | Restores SVR; supports HR mildly |
| Epinephrine | 0.01–0.05 mcg/kg/min (max 0.3) | Refractory shock or severe bradycardia | Inotropy + chronotropy |
| Phenylephrine | 0.1–0.5 mcg/kg/min (max 1–2) | Isolated vasodilation without bradycardia | Pure α1 → ↑ SVR without ↑ HR |
| Vasopressin | 0.01–0.04 units/min | Refractory states | Non-adrenergic vasoconstriction |
| Goal MAP | ≥ 65 | — | Higher goals sometimes used in spinal trauma |
ANAPHYLACTIC SHOCK
| Medication | Dose | When to Use | Key Notes |
|---|---|---|---|
| IM Epinephrine (first-line) | Adults: 0.3–0.5 mg / Kids: 0.01 mg/kg | All anaphylaxis with airway or hypotension | Reverses bronchospasm & vasodilation |
| IV Epinephrine | 0.1–0.5 mcg/kg/min (max 0.3) | Refractory to IM + fluids | Potent β1/β2/α1; monitor closely |
| Norepinephrine | 0.01–0.1 mcg/kg/min (max 1–2) | Persistent hypotension | Add-on if IV epi insufficient |
| Goal MAP | ≥ 65 | — | Treat airway + remove trigger |
RISKS and TREATMENT
| Risk / Issue | Details / Management |
|---|---|
| Tissue ischemia | Rare but possible; higher risk with norepinephrine or phenylephrine |
| Extravasation | Catecholamine extravasation reversible with phentolamine; vasopressin has no reversal agent |
| Kidney perfusion | Prolonged vasopressor use may reduce renal perfusion; monitor UOP and creatinine |
| Peripheral administration | Avoid > 24–48 hours to prevent tissue injury |
| Extravasation Management Steps | Notes |
|---|---|
| Stop infusion | Leave the catheter in place for possible antidote |
| Aspirate remaining drug | Do not flush the line |
| Elevate limb | Reduces edema and drug spread |
| Phentolamine injection | First-line for catecholamine extravasation; infiltrate around and through catheter site to create a vasodilation ring |
| Topical nitroglycerin 2% | Use if phentolamine unavailable; promotes local vasodilation |
| Warm compresses | Helps increase local blood flow |
| Monitor | Watch for ischemia, necrosis, pain, or sensory changes; escalate to surgery/plastics if needed |
I figured its important to quickly review the receptors so here is quick, easy, to the point bullets:
- α1 → 1 vessel = vasoconstriction
- α2 → 2 = negative feedback / inhibit NE
- β1 → 1 heart = heart effects
- β2 → 2 lungs = bronchodilation / vasodilation
- V1 --> vasoconstricts/ vascular smooth muscle
- V2 --> 2 kidneys= ADH collects water in kidneys
Sepsis / Septic Shock
Start a pressor when:
- The patient has received adequate fluids (30 mL/kg) and is still inadequately perfused
- Hypotension
- MAP < 65
- Lactate > 2 mmol/L
- AMS
- Low urine output
1. Norepinephrine (Levophed)
- Start: 0.05 mcg/kg/min
- Receptor profile: α1 agonist (vasoconstriction) with mild β1 effects (↑ HR & contractility)
2. Epinephrine
- Dose: 0.01–0.05 mcg/kg/min
- Use when norepinephrine is insufficient and additional inotropic support is needed.
3. Vasopressin
- Dose: 0.01–0.04 units/min
- Adjunct to norepinephrine
- BEST TO USE WHEN ACIDOTIC BECAUSE IT ACTS ON V1 RECEPTOR NOT AFFECTED BY LOW PH!
Goal: Titrate to MAP ≥ 65
Hypovolemic Shock
Start a pressor when hypotension persists despite adequate fluid resuscitation, especially when accompanied by:
- Low urine output
- Tachycardia
- AMS
Norepinephrine
- Start: 0.01–0.05 mcg/kg/min
- Increase by 0.01 mcg/kg/min as needed
- Max: 0.5 mcg/kg/min (severe shock)
Goal: MAP ≥ 65
Cardiogenic Shock
Defined by cardiac dysfunction, hypotension, and poor perfusion (cool extremities, low urine output).
After cautious fluid resuscitation, pressors may be needed.
1. Norepinephrine
- Dose: 0.01–0.03 mcg/kg/min
- Max: 0.5 mcg/kg/min
- Helps maintain MAP ≥ 65 and organ perfusion
>0.2 mcg/kg/min typically used in severe cases
2. Dobutamine
- Dose: 2–5 mcg/kg/min, titrate as needed
- Use for low cardiac output with preserved SVR
- Strong inotropic agent
3. Combination Therapy
Dobutamine + Norepinephrine
- Dobutamine ↑ inotropy
- Norepinephrine ↑ afterload, improves MAP & coronary perfusion
4. Milrinone
- Dose: 0.125–0.5 mcg/kg/min
- Consider if dobutamine is insufficient or in pulmonary hypertension
Neurogenic Shock
Often presents with bradycardia + hypotension due to loss of sympathetic tone (spinal injury, autonomic failure).
Significant vasodilation → requires pressors after fluids.
1. Norepinephrine
- Dose: 0.01–0.1 mcg/kg/min
- Titrate by 0.01–0.02 mcg/kg/min
2. Epinephrine
- Dose: 0.01–0.05 mcg/kg/min
- Titrate by 0.01–0.05 mcg/kg/min
- Max: 0.1–0.3 mcg/kg/min
- Helpful with severe bradycardia or when norepinephrine is inadequate
3. Phenylephrine
- Dose: 0.1–0.5 mcg/kg/min
- Titrate by 0.05–0.1 mcg/kg/min
- Max: 1–2 mcg/kg/min
- Pure α1 agonist → vasoconstriction without ↑ HR
- Useful in isolated vasodilation
4. Vasopressin
- Dose: 0.01–0.04 units/min
- Consider in refractory shock
- BEST TO USE WHEN ACIDOTIC BECAUSE ACTS ON V1 RECEPTOR AND NOT AFFECTED
Goal: MAP ≥ 65
Anaphylactic Shock
If hypotension persists despite fluids and IM epinephrine, start pressors.
1. IM Epinephrine (first-line)
- Adults: 0.3–0.5 mg (1:1000, 1 mg/mL)
- Kids: 0.01 mg/kg (max 0.3 mg/dose) IM
2. IV Epinephrine
- Dose: 0.1–0.5 mcg/kg/min
- Max: 0.1–0.3 mcg/kg/min
- Helps reverse bronchospasm, vasodilation, and increased vascular permeability
3. Norepinephrine
- Dose: 0.01–0.1 mcg/kg/min
- Titrate by 0.01–0.02 mcg/kg/min
- Max: 1–2 mcg/kg/min
Goal: MAP ≥ 65
Risks & Considerations with Vasopressors
- Tissue ischemia (rare but possible), especially with norepinephrine or phenylephrine
- Vasopressor extravasation risk—no reversal agent but.....
- Phentolamine = first-line antidote for catecholamine extravasation.
- Infiltrate around and through the catheter site with dilute phentolamine.
- Goal: create a ring to promote local vasodilation.
- If no Phentolamine then use 2% topical nitroglycerin to promote vasodilation.
- also use warm compresses
- Kidney perfusion reduction with prolonged use
- Avoid prolonged peripheral administration >24–48 hours
References
- Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021 (Intensive Care Medicine, 2021)
- Singer M, et al. Sepsis-3, JAMA, 2016
- EMGuideWire – Vasopressors in the ED
- EMCrit IBCC – Pressors
