AAP/ACAAI

Anaphylaxis: Epinephrine + Broselow

Calculate IM epinephrine dosing (0.01 mg/kg) and estimate pediatric weight by length using the Broselow method.

Epinephrine IM Dosing by Weight

Dose: 0.01 mg/kg IM of 1:1000 (= 1 mg/ml) epinephrine. Repeat every 5–15 min if no improvement.

1–150 kg
Your data never leaves this device. No accounts. No servers. No tracking.

Frequently Asked Questions About Anaphylaxis & Epinephrine

Anaphylaxis is a rapid, systemic hypersensitivity reaction characterized by sudden onset of urticaria/angioedema, respiratory distress, hypotension, GI symptoms, or loss of consciousness. Common triggers include foods, medications, insect venom, and latex.

First-line treatment is immediate IM epinephrine 0.01 mg/kg of 1:1000 solution (max single dose 0.5 mg adult, often capped at 0.3 mg for children), repeated every 5–15 minutes if no improvement. Lay patient supine with legs elevated, establish IV access, give antihistamines and corticosteroids, and observe for biphasic reaction (monitor ≥4–8 hours).

The 0.01 mg/kg (0.01 ml/kg of 1:1000) IM dose is supported by evidence from anaphylaxis registry data and consensus guidelines (Sicherer & Simons, Pediatrics 2017). This dose reliably reverses hypotension, urticaria, and airway symptoms in most cases. Higher doses increase risk of arrhythmia; lower doses may be inadequate.

The maximum single adult dose is capped at 0.5 mg per ACAAI/AAAAI guidelines. Many pediatric sources recommend capping children at 0.3 mg, though the 0.01 mg/kg calculation often produces lower values in younger children.

Auto-injector selection depends on weight and the 0.01 mg/kg target dose:

  • <7.5 kg: Ampule preferred; auto-injectors deliver fixed doses that may exceed 0.01 mg/kg target.
  • 7.5–14 kg: 0.1 mg auto-injector (Auvi-Q 0.1 mg or generic equivalent) or use ampule with syringe.
  • 15–29 kg: 0.15 mg auto-injector (EpiPen Jr, Auvi-Q 0.15 mg).
  • ≥30 kg: 0.3 mg auto-injector (EpiPen, Auvi-Q 0.3 mg).

These are US labeling guidelines. Repeat IM injection every 5–15 min if symptoms persist.

The Broselow tape (Lubitz et al., Ann Emerg Med 1988) is a color-coded length-to-weight estimation tool that divides children into 10 zones (Grey, Pink, Red, Purple, Yellow, White, Blue, Orange, Green, Green-extension). Each zone has an estimated weight range.

The tape is useful in emergency settings when weight is unknown. Important limitation: Broselow underestimates weight in older and obese children. Always use measured weight when available. Accuracy is ±10% in about 80% of children but can be off by 20%+ in outliers.

IM is first-line. The IM route (vastus lateralis or deltoid) is preferred because it reliably achieves therapeutic levels faster than subcutaneous (SQ). SQ is slower and not recommended for anaphylaxis.

IV epinephrine (as infusion, NOT bolus in anaphylaxis) is reserved for refractory hypotensive shock and requires ICU monitoring due to risk of arrhythmia. For anaphylaxis in the ED or pre-hospital setting, always use IM first.

After IM epinephrine, take these steps:

  • Lay supine with legs elevated (unless vomiting or respiratory distress) to maintain cerebral perfusion.
  • Assess response in 5–15 minutes. If symptoms persist or worsen, repeat IM epinephrine.
  • Establish IV access and give 0.5 L bolus (children: 20 ml/kg NS) for hypotension.
  • Give H1/H2 blockers (diphenhydramine 1 mg/kg, ranitidine if IV available) and corticosteroids (methylprednisolone 1–2 mg/kg or equivalent).
  • Observe ≥4–8 hours in ED for biphasic reaction (recurrence of symptoms 1–72 hours after initial onset, seen in ~1% of cases).
  • Discharge with auto-injectors and emergency action plan, including trigger avoidance.

Biphasic anaphylaxis is recurrence of anaphylaxis symptoms (commonly respiratory distress, hypotension, or urticaria) that develops 1–72 hours (median ~10 hours) after the initial episode, even after successful epinephrine treatment.

Risk factors include severe initial reaction, delayed epinephrine administration, or lack of adjunctive therapy. Management includes continued observation in hospital, repeat epinephrine if recurrence, and IV access maintained throughout.