Anaphylaxis

Aka: Anaphylaxis, Allergic Reaction

1. See Also
   1. Urticaria
2. Epidemiology: Anaphylaxis
   1. Incidence: 50 cases per 100,000 person-years
   2. Lifetime Prevalence: 0.05 to 2%
   3. Mortality: 1%
3. Risk Factors: Anaphylaxis
   1. Mild Asthma: Relative risk 2
   2. Severe Asthma: Relative risk 3
   3. Known Food Allergy, Hymenoptera Sting allergy or medication allergy
4. Precautions
   1. Anaphylaxis is a life threatening condition that requires immediate ABC Management and Epinephrine injection IM
   2. Biphasic reactions occur in up to 20% of cases
      1. Second acute anaphylactic reaction despite no repeat exposure to the original allergan
      2. Second reaction may be delayed up to 8 hours later (24-72 hour delay has been reported in atypical cases)
5. Causes: Common
   1. Idiopathic
      1. See Urticaria
      2. Consider mastocytosis
   2. Hymenoptera Allergy (Bees, wasps, fire ants)
      1. See insect sting
      2. Results in >50 fatal U.S. reactions per year
   3. Food Allergy (30% of anaphylactic episodes, especially in children under age 4 years)
      1. Cow's Milk
      2. Egg whites
      3. Fish
      4. Peanuts
      5. Tree nuts
      6. Sesame
      7. Food additives
      8. Shellfish
   4. Medications (most common in age over 55 years)
      1. Penicillin Allergy (75% of anaphylactic deaths)
      2. NSAIDs or Aspirin
      3. Radiographic Intravenous Contrast Material
      4. Allopurinol
      5. ACE Inhibitors
      6. Opioids
      7. Interferon
   5. Allergic Contact Dermatitis
      1. Latex Allergy
   6. Miscellaneous
      1. Animal dander
6. Signs: Anaphylaxis typical presentation
   1. Urticaria and Angioedema (90% of cases)
   2. Respiratory distress, especially upper airway obstruction (70% of cases)
      1. Lower airway obstruction may occur, especially in Asthma
   3. Cardiovascular collapse with Hypotension (45% of cases)
   4. Gastrointestinal symptoms such as Vomiting (45% of cases)
   5. Neurologic symptoms such as Headache or Dizziness (15% of cases)
7. Signs: Mild
   1. General
      1. Feeling impending doom
      2. Pruritus (uncommon without rash)
      3. Metallic Taste in mouth
   2. Naso-ocular
      1. Itchy nose or eyes
      2. Sneezing
      3. Clear, watery Eye Discharge or Nasal discharge
   3. Skin (occurs)
      1. Urticaria: Hives
      2. Angioedema: Facial swelling and Lip swelling
8. Signs: Moderate
   1. Neurologic
      1. Dizziness
      2. Weakness
   2. Gastrointestinal
      1. Nausea, Vomiting
      2. Bloody Diarrhea
      3. Abdominal Pain
      4. Fecal urgency or Incontinence
   3. Genitourinary
      1. Uterine cramps
      2. Urinary urgency or Incontinence
9. Signs: Severe
   1. Neurologic
      1. Syncope
      2. Seizures
   2. Respiratory: Angioedema of upper airway
      1. Hoarseness
      2. Dysphonia
      3. Lump in throat
      4. Bronchospasm
      5. Stridor or Wheezing
      6. Dyspnea and Tachypnea
   3. Cardiovascular
      1. Hypotension
      2. Arrhythmia
      3. Tachycardia
10. Labs: Confirms diagnosis (do not rely on labs to make or treat acute episode)
    1. Serum histamine
       1. Requires special handling for accuracy
       2. Obtain first level within 1 hour of symptom onset
       3. Compare to baseline level
    2. Serum tryptase
       1. Levels rise 30 minutes after onset and peak at 1-2 hours
       2. Obtain level on presentation, in 1-2 hours and 24 hours after presentation
11. Differential Diagnosis
    1. Hypovolemic, cardiogenic, neurogenic or septic shock
    2. See Flushing
    3. See Wheezing
    4. Panic Attacks
    5. Systemic mastocytosis
    6. Leukemia
    7. Hereditary Angioedema
12. Diagnosis: Anaphylaxis
    1. High likelihood if ONE of the following three criteria present
    2. Criteria 1: Acute illness onset within minutes to hours AND
       1. Skin or mucosal effects (e.g. Hives, Pruritus, Flushing, swollen lips/Tongue/uvula) AND
       2. Respiratory distress (e.g. Dyspnea, bronchospasm) or cardiovascular collapse (e.g. Hypotension, Syncope)
    3. Criteria 2: Acute illness onset within minutes to hours after likely allergan exposure AND a least TWO of the following
       1. Skin or mucosal effects (e.g. Hives, Pruritus, Flushing, swollen lips/Tongue/uvula)
       2. Respiratory distress (e.g. Dyspnea, bronchospasm)
       3. Cardiovascular collapse (e.g. Hypotension, Syncope)
       4. Gastrointestinal symptoms persist (e.g. abdominal cramping, Vomiting)
    4. Criteria 3: Hypotension within minutes to hours after likely allergan exposure
       1. General: 30% decrease in systolic Blood Pressure
       2. See Hypotension
       3. See Pediatric Vital Signs for age specific cut-offs for low Blood Pressure
    5. References
       1. Sampson (2006) Ann Emerg Med 47(4): 373-80
13. Management: Emergency Department
    1. General Measures
       1. ABC Management
       2. Oxygen
    2. Anaphylaxis with Airway Compromise
       1. Epinephrine is the mainstay of Anaphylaxis management and must not be delayed
          1. Administer within 5 minutes of presentation (surviving severe Anaphylaxis cases share rapid Epinephrine delivery in common)
             1. Sampson (1992) N Engl J Med 327(6): 380-84
          2. Narrow window of opportunity with Epinephrine prior to complete airway obstruction and cardiovascular collapse
          3. EpinephrineVasoconstricts, bronchodilates and decreases airway edema
       2. Epinephrine (1:1000 concentration = 1 mg/ml)
          1. Intramuscular dosing preferred over subcutaneous (due to more reliable and faster rise in blood levels)
          2. Repeat every 5 to 15 minutes prn up to 3 doses
          3. Cardiac monitoring required for repeat dosing
          4. Epinephrine via vial
             1. Adult: 0.5 mg (0.5 ml) IM
             2. Child: 0.01 mg/kg (0.01 ml/kg) IM up to 0.3 mg (0.3 ml)
          5. Epinephrine Autoinjector (preferred if available, as reduces errors and speeds delivery)
             1. Adult and children over 30 kg or 66 pounds: 0.3 mg autoinjector
             2. Children under 30 kg or 66 pounds: 0.15 autoinjector
       3. Unresponsive to Epinephrine
          1. Glucagon 3.5 to 5 mg IV if patient uses Beta-Blockers
             1. May repeat if no Blood Pressure response within 10 minutes
          2. Norepinephrine may also be considered
    3. Hypotension (due to vasodilitation and third spacing)
       1. Fluid Resuscitation with isotonic saline (NS, LR)
          1. Adult: 2 Liters Normal Saline
          2. Child: 10-20 ml/kg per bolus until Hypotension improves
          3. Large volumes may be required
       2. Pressors (e.g. Dopamine) may be required
       3. Consider Epinephrine by continuous IV infusion
    4. Respiratory distress
       1. Nebulized Beta adrenergic agonist (e.g. Albuterol)
          1. Consider for signs of lower airway obstruction
       2. Consider Endotracheal Intubation
    5. Urticaria, Pruritus or Flushing
       1. General: H1 Antagonists
          1. Not a first-line agent in Anaphylaxis management (us only as an adjunct to Epinephrine and ABC Management)
          2. Effects are delayed 1-2 hours from delivery
          3. Does not reverse upper airway obstruction or improve Hypotension
       2. Diphenhydramine (Benadryl) every 6 hours prn
          1. Adult: 25-50 mg IM/IV
          2. Child: 1.25 mg/kg IM/IV
    6. Severe or persistent symptoms not resolved in 30 min
       1. General: Corticosteroids
          1. Not a first-line agent in Anaphylaxis management (us only as an adjunct to Epinephrine and ABC Management)
          2. Effects are delayed 6 hours from delivery
          3. Consider for prevention of biphasic reaction
       2. Hydrocortisone 5 mg/kg IV
       3. Methylprednisolone (Solu-Medrol) every 6 hours
          1. Adult: 60-125 mg IV/IM
          2. Child: 0.5-1 mg/kg IV/IM
14. Disposition
    1. Observation of moderate to severe reactions for 6-10 hours
       1. Minimum observation time is 3 hours
       2. Prolonged reaction may require 24 hour observation
    2. Biphasic reactions occur several hours later in 20%
15. Management: Home
    1. Epinephrine Autoinjector (EpiPen, Twinject, Adrenaclick)
       1. Administer at onset of anxaphylaxis symptoms and present immediately for medical care or call 911
    2. Diphenhydramine (Benadryl)
       1. Adult: 25-50 mg PO q6h x3 days
       2. Child: 5 mg/kg/day PO divided q6h
    3. Prednisone
       1. Corticosteroids most effective if started early
          1. Administer within 1-2 hours if possible
       2. Adult: 60 mg PO qd x3 days
       3. Child: 0.5-1 mg/kg/dose PO qd x3 days
    4. Cimetidine (Tagamet)
       1. Adult: 400 mg PO bid x3 days
16. Prevention
    1. Medical Alert Bracelet should be worn
    2. Strict avoidance of allergen
    3. Epinephrine Autoinjector, home injectable devices (EpiPen, Twinject, Adrenaclick)
       1. Keep one in place where most of time spent
       2. Bring an injector when traveling
    4. Consider allergist referral
    5. Consider Skin Testing and Desensitization therapy
       1. Indicated if re-exposure is likely or unavoidable
    6. Clinic office administration of medications and injections should include a policy to observe patient after injection for 20-30 minutes
17. References
    1. Arnold (2011) Am Fam Physician 84(10): 1111-8
    2. Ben-Shoshan (2011) Allergy 66(1): 1-14
    3. Ellis (2003) CMAJ 169(4):307-11
    4. Sampson (2003) Pediatrics 111:1601-8
    5. Tang (2003) Am Fam Physician 68:1325-40
    6. Worth (2010) Expert Rev Clin Immunol 6(1): 89-100