FIELD REFERENCE
Full criteria & treatment guidance
Key cautions & base contact
- Epinephrine precedes diphenhydramine in anaphylaxis.
- The IM and IV/IO epinephrine concentrations differ tenfold; confirm indication, concentration, route, and dose.
Classify the presentation
- Rash/urticaria only, stable vital signs, and no anaphylaxis history follows the mild-reaction branch. If SpO₂ is below 95%, use the anaphylaxis branch.
- Anaphylaxis findings include hypotension, wheeze, hypoxia, stridor, intraoral swelling, GI symptoms, or impending obstruction.
- Facial/cervical angioedema alone has a separate treatment branch: one 0.5 mg IM epinephrine dose, held if an auto-injector was already given, plus oxygen and diphenhydramine as specified.
Treat anaphylaxis promptly
- Give epinephrine 0.5 mg IM into the lateral thigh using 1 mg/mL. Count a prearrival auto-injector as the first dose.
- Give high-flow mask oxygen or nasal cannula at 6 L/min as tolerated. Establish IV/IO; for hypotension, saline 250 mL boluses up to 1 L to maintain perfusion.
- For wheeze or room-air hypoxia below 95%, give albuterol 5 mg/6 mL by continuous nebulization as tolerated.
Persistent severe symptoms
- After 5 minutes, continued hypotension, respiratory distress, or impending airway obstruction permits a second 0.5 mg IM epinephrine dose OR 0.3 mg IV/IO using 0.1 mg/mL.
- Give diphenhydramine 50 mg IM/IV once after initial epinephrine; do not give it if taken before arrival.
Contact & transport
- Anaphylaxis requires base contact and ALS escort to a base-designated ERC. Reassess airway, breathing, BP, and recurrence after every intervention.
- Patients who self-treated with an epinephrine auto-injector still require ALS escort and evaluation even when symptoms are resolving.
VISUAL FIELD REFERENCE
Anaphylaxis: first dose → reassess → next step
Adult / adolescent · ALS
Anaphylaxis branch only. Continue airway, oxygen, perfusion, and other indicated care alongside these checkpoints.
First-line IM epinephrine
Give epinephrine 0.5 mg IM into the lateral thigh using 1 mg/mL. Count a prearrival auto-injector as the first dose.
Persistent severe symptoms after 5 minutes
After 5 minutes, continued hypotension, respiratory distress, or impending airway obstruction permits a second 0.5 mg IM epinephrine dose OR 0.3 mg IV/IO using 0.1 mg/mL.
Diphenhydramine follows epinephrine
Give diphenhydramine 50 mg IM/IV once after initial epinephrine; do not give it if taken before arrival.
- Anaphylaxis requires base contact and ALS escort to a base-designated ERC. Reassess airway, breathing, BP, and recurrence after every intervention.
- The IM and IV/IO epinephrine concentrations differ tenfold; confirm indication, concentration, route, and dose.
Selected checkpoints; read the complete guide for criteria, exclusions, doses, and ongoing care. SO-M-015
UNDERSTAND THE CARE
Why the reaction branch matters
The local order separates stable rash-only illness, isolated facial/cervical angioedema and systemic anaphylaxis. These branches have different medication instructions. Describe airway swelling, breathing, oxygenation and perfusion explicitly so the chosen branch is clear. A patient’s prior auto-injector is part of the treatment record rather than a reason to restart the dose count.
Applying the guidance
Epinephrine precedes the adjunctive antihistamine in the anaphylaxis pathway. Prepare the correct product for the selected route and verify the concentration before administration; the IM and IV/IO concentrations are not interchangeable. Continued assessment looks for persistent airway obstruction, respiratory distress or hypotension and applies the repeat criteria in the full guide.
Putting it together
Teaching example: a patient used an auto-injector before EMS arrival and now reports feeling better. Identify the dose and time, reassess the whole presentation, count prior treatment and retain the required ALS evaluation, contact and transport pathway.
Diagram text & teaching checkpoints
- Classify
- Rash only, isolated angioedema, or systemic findings.
- First-line care
- Use the appropriate epinephrine branch.
- Reassess
- Airway, breathing, perfusion and prior doses.
- Contact and transport
- Improvement does not erase the requirement.
Sources for this explanation
Original OCMedic teaching synthesis of the references below. Educational expansion updated ; this is not a new independent clinical-review date. Source-specific dates and limitations remain in the full guidance.