Anaphylaxis

Background

Definition

Anaphylaxis is highly likely when ANY ONE of the following criteria is fulfilled

Criterion 1 (90% of patients)

1. Acute onset of an illness involving the skin, mucosal tissue, or both AND at least one of the following:
   1. Respiratory Compromise
   2. Reduced blood pressure or associated symptoms (Syncope, Dizziness)

Criterion 2 (10-20% of pts)

1. TWO OR MORE of the following that that occur rapidly after exposure to a LIKELY allergen for that patient
   1. Involvement of the skin-mucosal tissue (hives, swollen lips-tongue-uvula)
   2. Respiratory compromise
   3. Hypotension or associated symptoms
   4. Persistent gastrointestinal symptoms: (vomiting, diarrhea, crampy abdominal pain)

Criterion 3

1. Hypotension after exposure to a KNOWN allergy for that patient (minutes to hours):
   1. Adults: systolic blood pressure (SBP) <90 mmHg or >30% reduction from baseline
   2. Pediatrics
      1. 1 month - 1 year: SBP <70 mmHg
      2. 1 year - 10 years: SBP <(70 mmHg + [2 x age])
      3. 11 years - 17 years: SBP <90 mmHg

Clinical Features

Raised urticaria

Angioedema of tongue

• Cutaneous symptoms: 90%
• Respiratory symptoms: 70%
• Gastrointestinal symptoms: 40%
• Cardiovascular symptoms: 35%

Differential Diagnosis

Acute allergic reaction

• Allergic reaction/urticaria
• Anaphylaxis
• Angioedema
• Anxiety attack
• Asthma exacerbation
• Carcinoid syndrome
• Cold urticaria
• Contrast induced allergic reaction
• Scombroid
• Shock
• Transfusion reaction

Management

1. Epinephrine
   1. 1:1000 IM 0.3 - 0.5mg (0.3 - 0.5mL) every 5 - 15 minutes
      1. Give as soon as possible
      2. Always IM initially
      3. If response to IM is inadequate: give epinephrine infusion 1:10,000 2 - 10 µg/min
      4. How to make a quick epi drip: Take your code-cart epi (it doesn't matter if it's 1:1,000 or 1:10,000) and inject 1mg into a liter bag of NS. Final concentration is 1mcg/ml. Run at 1cc/min and titrate to effect.
   2. Pediatric: Epinephrine 1:1000 0.01 mg/kg (max 0.5mg) IM every 5 to 15 minutes
      1. IV infusion: 0.05 - 1 mcg/kg/min
2. Supplemental oxygen
   1. Consider endotracheal intubation if airway edema present
3. Normal saline bolus
   1. If unresponsive to epinephrine assume distributive shock and give 1 - 2 liters of normal saline
4. Glucagon
   1. 1 - 2mg IV over 5 minutes followed by infusion of 5 - 15 µg/min
   2. If taking beta-blocker AND unresponsive to epinephrine
5. Also consider
   1. Albuterol
      1. for bronchospasm resistant to IM epinephrine
   2. Antihistamines (for symptom control AFTER hemodynamically stable)
      1. Diphenhydramine: 25 to 50 mg IV
      2. Ranitidine: 50 mg IV (minimal evidence to support this)
   3. Glucocorticoid
      1. MAY blunt biphasic reaction although little evidence to support usage
      2. Methylprednisolone: *125 mg IV (2mg/kg in children)
      3. Dexamethasone: 10mg IV or PO (0.6mg/kg in children)

Expected Course

Uniphasic (80-90%)

• • Symptoms peak within 30 minutes to 1 hour after onset, resolve within 30 minutes to 1 hour of receiving treatment

Biphasic (10-20%)

• • Uniphasic response, followed by asymptomatic period of hour or more, then return of symptoms
  • The second phase does not necessarily resemble the first!
  • More likely with a severe initial presentation, hypotension, and recurrent epinephrine dosing requirements in the emergency department
  • Little evidence to support the use of discharge steroids to prevent a biphasic reaction
  • 0.4% of patients with anaphylaxis had a rebound event while in the ED

Disposition

Admit

Severe and moderate presentations especially if symptoms did not respond promptly to epinephrine or required repeat dosing

Discharge

• Symptom-free for at least 4 hours and mild initial presentation
• Send home with an epinephrine autoinjector! (Epi-Pen)
• Up to 6% of the people with anaphylaxis have a repeat ED visit for anaphylaxis within 7 days

See Also

• Allergic Reaction
• Angioedema (Upper Airway)

Sources

• Brown SGA, Mullins RJ and Gold MS. Anaphylaxis: diagnosis and management, MJA 2006; 185: 283–289
• Ewan PW. ABC of allergies – Anaphylaxis, BMJ 1998; 316: 1442-1445
• Simons FER, Gu X, Simons KJ. Epinephrine absorption in adults: Intramuscular versus subcutaneous injection, J Allergy Clin Immunol 2001;108:871-3
• Lieberman P et al. The diagnosis and management of anaphyalxis: An updated practice parameter, J Allergy Clin Immunol 2005;115;3:S483-S523
• Sheikh A, Shehata YA, Brown SGA, Simons FER. Adrenaline (epinephrine) for the treatment of anaphylaxis with and without shock. Cochrane Database of Systematic Reviews 2008, Issue 4. Art. No.: CD006312. DOI:10.1002/14651858.CD006312.pub2
• Second symposium on the definition and management of anaphylaxis: summary report--Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium.