10.3 Pediatric Anaphylaxis & Severe Allergic Reactions

BCEN CPEN Certified Pediatric Emergency Nurse Exam

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1 Chapter 1: Exam Overview, Triage Process & Initial Emergency Assessment

1.1 CPEN Exam Logistics, Blueprint & Certification Overview 1.2 Pediatric Triage Systems & Acuity Categorization 1.3 Pediatric Assessment Triangle (PAT) & Initial Impression 1.4 Primary & Secondary Pediatric Emergency Assessment 1.5 Age-Specific Vital Signs, Developmental Considerations & Pain Scales

2 Chapter 2: Pediatric Respiratory Emergencies

2.1 Upper Airway Obstruction 2.2 Lower Airway Emergencies 2.3 Respiratory Distress vs. Respiratory Failure & Airway Management

3 Chapter 3: Pediatric Cardiovascular Emergencies

3.1 Pediatric Dysrhythmias & ECG Analysis 3.2 Congenital Heart Defects 3.3 Acquired Heart Disease & Heart Failure

4 Chapter 4: Pediatric Neurological Emergencies

4.1 Pediatric Seizures, Status Epilepticus & Febrile Seizures 4.2 Altered Mental Status, Increased ICP & Head Trauma 4.3 Pediatric Central Nervous System Infections

5 Chapter 5: Pediatric Gastrointestinal & Genitourinary Emergencies

5.1 Pediatric GI Surgical Emergencies 5.2 Pediatric Dehydration, Gastroenteritis & Fluid Resuscitation Protocols 5.3 Pediatric GU & Renal Emergencies

6 Chapter 6: Pediatric Endocrine, Metabolic & Hematologic/Oncologic Emergencies

6.1 Diabetic Ketoacidosis (DKA) & Hypoglycemia in Pediatric Emergency Patients 6.2 Electrolyte Imbalances & Inborn Errors of Metabolism 6.3 Sickle Cell Disease Crisis & Pediatric Oncologic Emergencies

7 Chapter 7: Pediatric Musculoskeletal, Integumentary & ENT/Ophthalmic Emergencies

7.1 Pediatric Musculoskeletal Injuries & Fractures 7.2 Pediatric Dermatologic Emergencies & Rashes 7.3 Pediatric ENT & Ocular Emergencies

8 Chapter 8: Pediatric Trauma Emergencies

8.1 Pediatric Trauma Resuscitation & Anatomical Vulnerabilities 8.2 Head, Spinal & Thoracic Trauma in Children 8.3 Abdominal, Pelvic & Extremity Trauma in Pediatric Patients

9 Chapter 9: Child Maltreatment, Toxicology & Behavioral Emergencies

9.1 Child Abuse, Neglect, Non-Accidental Trauma & Mandatory Reporting 9.2 Pediatric Toxicology, Toxidromes & Emergency Antidotes 9.3 Pediatric Behavioral & Mental Health Crisis Management

10 Chapter 10: Pediatric Multi-System Emergencies, Shock & Thermal Injuries

10.1 Pediatric Shock Recognition & Classification 10.2 Pediatric Sepsis, Septic Shock & Multiple Organ Dysfunction Syndrome 10.3 Pediatric Anaphylaxis & Severe Allergic Reactions 10.4 Submersion Injuries, Drowning & Thermal/Burn Emergencies

11 Chapter 11: Professional Practice, Legal, Ethical & Safety Standards

11.1 Legal & Ethical Considerations 11.2 Patient Safety, Medication Error Prevention & Weight-Based Dosing 11.3 Family-Centered Care, Communication & Disaster/Surge Preparedness

10.3 Pediatric Anaphylaxis & Severe Allergic Reactions

Key Takeaways Explain This Topic AI

Anaphylaxis is a severe, systemic, life-threatening IgE-mediated or non-IgE-mediated hypersensitivity reaction characterized by rapid onset of airway, breathing, or circulatory compromise.

Intramuscular (IM) Epinephrine 1:1,000 (1 mg/mL) at a dosage of 0.01 mg/kg (maximum 0.3 mg in prepubertal children, 0.5 mg in adolescents) into the anterolateral thigh is the absolute first-line treatment and must be given immediately.

Patient positioning is critical: patients must remain supine with legs elevated (unless respiratory distress mandates head elevation); abrupt standing or sitting can precipitate fatal 'empty ventricle syndrome' due to sudden vena cava collapse.

Second-line medications (H1/H2 antihistamines and systemic corticosteroids) treat cutaneous symptoms and may mitigate biphasic reactions but DO NOT reverse airway edema or circulatory collapse.

Refractory anaphylaxis in patients receiving beta-blocker therapy may fail to respond to Epinephrine and requires IV/IO Glucagon (1–5 mg or 20–30 mcg/kg) to bypass blocked beta-receptors via direct adenylate cyclase activation.

Last updated: July 2026

10.3 Pediatric Anaphylaxis & Severe Allergic Reactions

Anaphylaxis is a severe, life-threatening systemic hypersensitivity reaction characterized by rapid onset of airway, breathing, or circulatory compromise. It results from the massive, sudden release of inflammatory mediators—including histamine , leukotrienes , tryptase , and platelet-activating factor (PAF) —from tissue mast cells and circulating basophils . In pediatrics, common triggers include foods (peanuts, tree nuts, milk, eggs, shellfish), medications (beta-lactam antibiotics, NSAIDs), insect stings (Hymenoptera), and latex. Delay in administering intramuscular Epinephrine is the single most consistent factor contributing to pediatric anaphylaxis fatalities.

Diagnostic Criteria for Pediatric Anaphylaxis

According to the National Institute of Allergy and Infectious Disease (NIAID) and Food Allergy and Anaphylaxis Network (FAAN) criteria, anaphylaxis is highly likely when ANY ONE of the following three clinical scenarios is met: +-----------------------------------------------------------------------------------------+

| NIAID/FAAN ANAPHYLAXIS DIAGNOSTIC CRITERIA |
+-----------------------------------------------------------------------------------------+
| SCENARIO 1: ACUTE SKIN/MUCOSA + RESPIRATORY OR CIRCULATORY COMPROMISE |
| - Acute onset (minutes to hours) involving skin/mucosal tissue (urticaria, flushing, |
| swollen lips/tongue/uvula) PLUS AT LEAST ONE OF: |
| a) Respiratory compromise (dyspnea, wheezing, stridor, hypoxemia) |
| b) Reduced BP or end-organ dysfunction (syncope, hypotonia, incontinence) |
+-----------------------------------------------------------------------------------------+
| SCENARIO 2: TWO OR MORE SYSTEMS INVOLVED AFTER LIKELY ALLERGEN EXPOSURE |
| - Two or more of the following occurring rapidly after exposure to a LIKELY allergen: |
| a) Skin/mucosal involvement (hives, itch, flushing, angioedema) |
| b) Respiratory compromise (dyspnea, stridor, wheeze) |
| c) Reduced BP or associated symptoms (collapse, syncope) |
| d) Persistent gastrointestinal symptoms (cramping abdominal pain, vomiting) |
+-----------------------------------------------------------------------------------------+
| SCENARIO 3: HYPOTENSION AFTER KNOWN ALLERGEN EXPOSURE |
| - Reduced BP after exposure to a KNOWN allergen for that specific patient: |
| - Infants/Children: Low SBP for age or > 30% decrease in SBP |
| - Adolescents: SBP < 90 mmHg or > 30% decrease from baseline |
+-----------------------------------------------------------------------------------------+

CPEN Exam Tip : Skin symptoms (hives, angioedema) are absent in up to 10–20% of anaphylactic episodes! Never rule out anaphylaxis simply because urticaria is not present, especially if acute respiratory distress or hypotension follows a food or medication exposure.

First-Line Pharmacotherapy: Intramuscular Epinephrine

Epinephrine is the single primary life-saving medication for anaphylaxis. There are no absolute contraindications to epinephrine in a patient experiencing anaphylaxis.

Pharmacological Actions of Epinephrine

α 1 \alpha_1 α 1 -adrenergic receptor agonist : Induces intense vasoconstriction, reversing peripheral vasodilation, reducing mucosal vascular permeability, and relieving airway edema and cutaneous angioedema.

β 1 \beta_1 β 1 -adrenergic receptor agonist : Increases myocardial contractility (inotropy) and heart rate (chronotropy), boosting cardiac output.

β 2 \beta_2 β 2 -adrenergic receptor agonist : Causes powerful bronchial smooth muscle relaxation (bronchodilation) and inhibits further mast cell and basophil degranulation (mediator suppression).

Administration Protocol & Dosing Guidelines

Concentration : Epinephrine 1:1,000 (1 mg/mL) formulation.

Dose : 0.01 mg/kg IM (equivalent to 0.01 mL/kg 0.01 \text{ mL/kg} 0.01 mL/kg of 1:1,000 solution).

Maximum single dose (prepubertal children): 0.3 mg ( 0.3 mL 0.3 \text{ mL} 0.3 mL ).

Maximum single dose (adolescents/adults): 0.5 mg ( 0.5 mL 0.5 \text{ mL} 0.5 mL ).

Autoinjector Weight-Based Dosing :

Infant Autoinjector ( 0.1 mg 0.1 \text{ mg} 0.1 mg ): Weight 7.5 kg to 15 kg.

Junior Autoinjector ( 0.15 mg 0.15 \text{ mg} 0.15 mg ): Weight 15 kg to 30 kg.

Adult Autoinjector ( 0.3 mg 0.3 \text{ mg} 0.3 mg ): Weight ≥ 30 kg \ge 30 \text{ kg} ≥ 30 kg .

Route & Site : Intramuscular (IM) injection into the mid-anterolateral thigh (vastus lateralis muscle) . Subcutaneous injection must be avoided due to delayed absorption caused by local vasoconstriction.

Frequency : Repeat every 5 to 15 minutes if clinical symptoms persist or worsen. Up to 20% of pediatric anaphylactic reactions require a second dose of epinephrine.

Parameter Recommended Specification
Drug & Concentration Epinephrine 1:1,000 (1 mg/mL)
Pediatric Dose 0.01 mg/kg IM (0.01 mL/kg)
Max Single Dose 0.3 mg (children) / 0.5 mg (adolescents)
Route & Site Intramuscular (IM) into vastus lateralis (mid-outer thigh)
Repeat Interval Every 5 to 15 minutes as needed
Emergency Airway Management & Patient Positioning
Airway Management Escalation

Laryngeal edema and tongue angioedema can cause complete upper airway obstruction within minutes. Emergency nursing interventions include:

Administer 100 % 100\% 100% high-flow oxygen via non-rebreather mask.

Nebulized Racemic Epinephrine ( 0.5 mL 0.5 \text{ mL} 0.5 mL of 2.25% solution in 3 mL 3 \text{ mL} 3 mL normal saline) or L-epinephrine for stridor and upper airway swelling.

Prepare for early endotracheal intubation if hoarseness, stridor, or severe uvular edema progresses. Select an endotracheal tube size 0.5 to 1.0 mm smaller than standard for age to accommodate laryngeal edema.

Patient Positioning: Prevention of "Empty Ventricle Syndrome" CORRECT POSITIONING FATAL POSITIONING ERROR
+-------------------------+ +-------------------------+
| SUPINE WITH LEGS ELEVATED| | ABRUPT STANDING / SITTING|
| Maintains venous return | | Sudden venous pooling |
| to cardiac chambers | | -> Vena Cava Collapse |
| | | -> Empty Ventricle |
| | | -> Sudden Cardiac Arrest|
+-------------------------+ +-------------------------+

CRITICAL CPEN SAFETY MANDATE : Patients in anaphylactic shock MUST be kept supine with their legs elevated . If respiratory distress makes lying flat intolerable, elevate the head slightly, but NEVER allow the child to stand up or sit upright suddenly . Massive venodilation causes blood pooling in the splanchnic bed and lower extremities. Abruptly standing up causes immediate venous collapse, leading to zero preload, empty ventricular contraction, profound bradycardia, and sudden cardiac arrest ("empty ventricle syndrome").

Refractory Anaphylaxis & Glucagon Therapy

Refractory anaphylaxis is defined as persistent shock or airway obstruction despite repeated IM epinephrine doses and aggressive fluid resuscitation (20 mL/kg isotonic crystalloid boluses).

Continuous Epinephrine Infusion : Initiate continuous IV/IO Epinephrine infusion at 0.05 to 1.0 mcg/kg/min titrated to blood pressure and perfusion.

Glucagon Administration for Beta-Blocker Patients : Patients taking chronic beta-blocker therapy (e.g., propranolol for dysrhythmias or hemangiomas) may be resistant to epinephrine because their cardiac beta-receptors are blocked.

Mechanism : Glucagon binds to non-beta glucagon receptors on cardiomyocytes, stimulating adenylate cyclase directly to produce cAMP, exerting positive inotropic and chronotropic effects independent of beta-receptors.

Pediatric Glucagon Dose : 20–30 mcg/kg IV/IO (maximum single dose 1–5 mg) given over 3–5 minutes, followed by a continuous infusion of 5–15 mcg/min.

Second-Line Adjunctive Therapies & Biphasic Monitoring

Antihistamines and corticosteroids are second-line adjunctive agents . They MUST NEVER be administered in place of or prior to Epinephrine.

H 1 \mathbf{H_1} H 1 -Antihistamines : Diphenhydramine ( 1 mg/kg 1 \text{ mg/kg} 1 mg/kg IV/IM, max 50 mg 50 \text{ mg} 50 mg ). Relieves pruritus and hives.

H 2 \mathbf{H_2} H 2 -Antihistamines : Famotidine ( 0.5 mg/kg 0.5 \text{ mg/kg} 0.5 mg/kg IV, max 20 mg 20 \text{ mg} 20 mg ). Provides dual histamine blockade.

Systemic Corticosteroids : Methylprednisolone ( 1 − 2 mg/kg 1-2 \text{ mg/kg} 1 − 2 mg/kg IV) or Dexamethasone ( 0.6 mg/kg 0.6 \text{ mg/kg} 0.6 mg/kg IV/IM). Onset of action takes 4 to 6 hours; administered primarily to decrease the risk of biphasic reactions .

Biphasic Reactions : A recurrence of anaphylactic symptoms hours after complete resolution of the initial event, occurring without re-exposure to the allergen. Biphasic reactions occur in up to 20% of cases, typically within 1 to 72 hours (peak 4–12 hours). Patients requiring multiple epinephrine doses or presenting with severe initial shock must be observed in the ED or pediatric ICU for at least 4 to 8 hours .