Anaphylaxis

A 14-year-old female presents to the emergency department with urticaria, respiratory distress, and recurrent vomiting after accidental ingestion of peanut-containing food. 

The patient has a known peanut allergy and was at a birthday party where she unknowingly consumed a dessert containing peanuts. Within 10–15 minutes, she developed generalized itching and hives, followed by coughing, wheezing, shortness of breath, and multiple episodes of vomiting. She has not taken any medications prior to arrival.  

Vitals: T 36.8°C, HR 120 bpm, RR 32/min, BP 110/70 mmHg, SpO₂ 98% on room air. 
General: Alert but anxious and in mild respiratory distress. 
HEENT: Mucous membranes moist, no stridor, no swelling of lips, oropharynx clear without pooling of secretions or swelling of the uvula.
Lungs: Diffuse biphasic wheezing, tachypnea with mild accessory muscle use. 
Cardiovascular: Tachycardic, regular rhythm. Normal S1 and S2, no murmurs. Strong distal pulses and capillary refill <2 seconds. 
Abdomen: Normoactive bowel sounds, soft, non-tender, with active vomiting episodes. 
Neurologic: Alert, oriented x3, no focal deficits, PERRL, EOMI, conversant with examiner.  
Skin: Diffuse urticaria involving trunk and extremities, no angioedema of lips or tongue noted. 

• Anaphylaxis – Most likely diagnosis given rapid onset of symptoms after exposure to a known allergen, with involvement of multiple organ systems (skin, respiratory, and gastrointestinal).
• Acute asthma exacerbation – Wheezing and respiratory distress are present, but these symptoms are part of a broader allergic reaction rather than an isolated asthma flare which would not account for skin and gastrointestinal symptoms. 

This is a case of anaphylaxis, defined as a serious allergic reaction involving two or more organ systems after exposure to a likely allergen. Respiratory and gastrointestinal symptoms combined with cutaneous findings are diagnostic, even in the absence of hypotension. Prompt administration of intramuscular epinephrine is lifesaving and should not be delayed. 

Initial Evaluation

• Laboratory studies are not required to diagnose anaphylaxis and should not delay treatment. Anaphylaxis is a clinical diagnosis.

Management

• Administer intramuscular (IM) epinephrine immediately, preferably into the lateral thigh. This dose can be repeated as indicated every 5-15 minutes for recurrence of symptoms or if the symptoms do not improve after the initial dose. Dose and type of IM epinephrine administration depends on weight (5-25kg EpiPen Jr, >25kg EpiPen). 

• Assess and manage the patient’s ABCs. Nebulized racemic epinephrine is helpful for upper airway obstruction (such as stridor), while nebulized albuterol is helpful for bronchospasm symptoms (such as wheezing). Hypotension should be treated with 20mL/kg isotonic crystalloid bolus (such as normal saline or lactated ringers) in addition to IM epinephrine.  

• Consider adjunctive medications such as antihistamines (H1 or H2 blockers) to relieve symptoms, hives/itch, and potential abdominal symptoms. These include diphenhydramine, cetirizine, and/or famotidine.  

• Also consider administering steroids (methylprednisolone, prednisone, prednisolone, or dexamethasone), though this may not be necessary in children that respond well to epinephrine. There is no clear evidence that steroid administration can reduce the incidence of biphasic reactions, but steroids are frequently given in practice.  

• Anaphylaxis is a clinical diagnosis characterized by multi-system involvement after allergen exposure. The presence of two or more of the following occurring rapidly after exposure to a likely allergen meet the criteria for anaphylaxis:
  • Involvement of the skin or mucosal tissue (generalized urticaria, pruritus or flushing, swollen lip, tongue, or uvula)
  • Respiratory compromise
  • Hypotension or associated symptoms of end-organ dysfunction
  • Persistent GI symptoms including significant abdominal pain and/or significant emesis
  • Patients with hypotension alone after exposure to known antigen also meet criteria for anaphylaxis and though most patients experience skin symptoms, ~10% do not have any skin manifestations and can have the most severe symptoms.
• Epinephrine is the first and most important treatment. Intramuscular epinephrine is the cornerstone of management, and no other medication (antihistamines, steroids, albuterol) should delay or substitute it. If in doubt, give epinephrine. One of the risks for a severe or even fatal anaphylaxis reaction is delayed administration of epinephrine.
• Biphasic reactions can occur hours after initial symptom resolution—monitor accordingly. The most important risk factors for a biphasic reaction include history of biphasic reactions, persistent symptoms, hypotension, severe asthma, requiring >1 epinephrine dose, or a drug trigger. Up to 20% of patients may experience symptom recurrence without re-exposure, typically within 4–8 hours. Ensure adequate ED observation time and educate families on the need for repeat epinephrine use if symptoms recur. 

Answers

Q1. False. As many as 10% of patients present without cutaneous findings and often have more severe symptoms.

Q2. False. Up to 20% of patients have a biphasic reaction and observation time in the emergency department depends on patient risk factors for such reaction.

Q3. E. Epinephrine is the medication of choice and first line treatment of anaphylaxis. The mechanism of action includes adrenergic stimulation to decrease airway edema, cause bronchodilation, increase cardiac output by increasing heart rate and vascular tone.   

• CHOP Emergency Department Clinical Pathway for Evaluation/Treatment of Children with Anaphylaxis.
• UpToDate: Anaphylaxis: Emergency Treatment
• StatPearls: Anaphylaxis
• Podcast - Cincinnati Children’s Hospital