In pediatric patients with acute upper airway mucosal edema such as anaphylaxis, allergic angio‑edema, or moderate‑to‑severe viral croup, when is adrenaline indicated and what are the recommended dosing regimens?

Adrenaline (Epinephrine) for Pediatric Mucosal Edema

Intramuscular epinephrine is the first-line emergency treatment for pediatric upper airway mucosal edema caused by anaphylaxis or severe allergic reactions, while nebulized racemic epinephrine is indicated for moderate-to-severe viral croup. 1, 2

Anaphylaxis and Allergic Angioedema

Primary Indication

• Epinephrine is the medication of choice for anaphylaxis through its vasoconstrictor effects that prevent or decrease upper airway mucosal edema (laryngeal edema), hypotension, and shock. 1
• Delayed epinephrine administration is associated with increased risk of hospitalization and poor outcomes including hypoxic-ischemic encephalopathy and death, while prompt prehospital injection is associated with lower risk of hospitalization and fatality. 1

Dosing Regimen for Anaphylaxis

• Children ≤30 kg (66 lbs): 0.01 mg/kg (0.01 mL/kg) of 1:1000 concentration, up to maximum 0.3 mg (0.3 mL), intramuscularly into the anterolateral thigh every 5-10 minutes as necessary. 3
• Children >30 kg (66 lbs) and adults: 0.3 to 0.5 mg (0.3 to 0.5 mL) of 1:1000 concentration intramuscularly into the anterolateral thigh every 5-10 minutes as necessary. 3
• The intramuscular route in the lateral thigh is the preferred method for parenteral administration, providing rapid absorption and effect. 4, 5

When to Administer

• Administer immediately when anaphylaxis is highly likely based on clinical criteria: acute onset with skin/mucosal involvement (urticaria, angioedema, flushing) PLUS respiratory compromise (dyspnea, wheeze, stridor) OR reduced blood pressure/end-organ dysfunction. 1
• For patients with known allergen exposure who previously experienced anaphylaxis, administer promptly at symptom onset even before life-threatening symptoms fully develop. 1
• Self-injectable epinephrine should be prescribed for any child with history of anaphylaxis to triggers that may be re-encountered outside medical settings, or for generalized acute urticaria after insect sting (10% risk of severe future reaction). 1

Viral Croup (Laryngotracheobronchitis)

Indication for Nebulized Epinephrine

• Nebulized racemic epinephrine is indicated for moderate-to-severe croup with significant stridor at rest, respiratory distress, or retractions. 6, 2, 4
• Epinephrine is recommended as first-line treatment for moderate-to-severe croup alongside corticosteroids. 4

Dosing Regimen for Croup

• Nebulized racemic epinephrine: 0.5 mL of 2.25% solution diluted in 2.5 mL of normal saline, administered via nebulizer; safe for all ages. 6
• Alternative: L-epinephrine (standard epinephrine) 0.5 mg/kg (maximum 5 mg) diluted in 3-5 mL normal saline can be used, as evidence shows no significant difference between racemic and L-epinephrine formulations. 2

Clinical Effect and Monitoring

• Nebulized epinephrine produces clinically and statistically significant transient reduction of croup symptoms at 30 minutes post-treatment, but this effect is not sustained at 2 and 6 hours. 2
• Children requiring two epinephrine treatments should be hospitalized for observation and further management. 6
• Observe for minimum 2-4 hours after epinephrine administration due to transient effect and risk of symptom recurrence. 2

Critical Safety Considerations

Route-Specific Warnings

• Never inject into buttocks, digits, hands, or feet due to risk of tissue ischemia. 3
• The intramuscular route is safer than intravenous administration, with lower risk of serious cardiac adverse effects. 5

Monitoring Requirements

• Patients receiving epinephrine for anaphylaxis should be observed for 4-6 hours, particularly those with severe symptoms or requiring multiple doses, due to 1-20% risk of biphasic reactions (typically occurring around 8 hours but up to 72 hours later). 7
• Vital signs should be monitored every 15 minutes until complete symptom resolution, then every 30-60 minutes until discharge. 7

Contraindications and Precautions

• There are no absolute contraindications to epinephrine for anaphylaxis—the presence of sulfites in the formulation should not deter use. 3
• Use with caution in patients with underlying heart disease, as epinephrine may aggravate angina or produce ventricular arrhythmias. 3
• Patients with hyperthyroidism, Parkinson's disease, diabetes, and pheochromocytoma are at greater risk of adverse reactions. 3

Common Pitfalls to Avoid

• Do not delay epinephrine administration while waiting for other treatments or diagnostic confirmation—prompt administration is critical for preventing poor outcomes. 1
• Do not confuse 1:1000 concentration (for IM/SC use) with 1:10,000 concentration (for IV use), as this can lead to dosing errors. 8
• Do not use epinephrine routinely for asthma exacerbations without concomitant anaphylaxis or angioedema, as selective β2-agonists are first-line with similar efficacy and better safety profile. 9
• Ensure all patients discharged after epinephrine administration receive two epinephrine autoinjectors, written emergency action plan, proper training on autoinjector use, and follow-up with allergist within 6-12 months. 7