Anaphylaxis

Presentation

Urticaria (hives), angioedema(swelling) and difficulty breathing

History

Patients often report a sense of impending doom (angor animi)
Onset is usually in minutes to 1 hour of exposure
Does the patient have any known allergies?
Is the patient complaining of pruritis?
Patient will often complain about G symptoms: nausea, vomiting, cramps and pain

Ask about ingestion of or exposure to common allergens:

  • Drugs: antibiotics, NSAIDs, contrast media
  • Latex: health-care worker, previous multiple surgeries, any other latex esposures
  • Food: more common in children but can present in adulthood, common adulthood allergens are peanuts, tree nuts, fish and crustaceans
  • Venom: common insects include bee, wasp, hornets or fire ants
  • Receiving allergen immunotherapy
  • Rare: exercise-induced either on its own or after the ingestion of food

Examination Findings

A Stridor, hoarse voice, throat closure
B shortness of breath, chest tightness, wheeze, cyanosis
C signs of shock, clammy, pale

Urticaria, erythema, angioedema
Facial flushing
Rhinitis
Wheeze
Stridor and hoarse voice is a sinister sign

Vital Signs

Tachycardia
Hypotension (if in shock)

Anaphylaxis is a clinical diagnosis based on history and examination findings treatment MUST NOT be delayed by investigations

Management

ABCDE approach

  1. Secure the airway, intubate if obstruction is imminent
  2. Give 100% oxygen
  3. Give IM adrenaline 0.5mg (0.5mL of 1:1000), repeat every 5 minutes as required while assessing pulse, blood pressure and respiratory function
  4. Secure IV access
  5. Give antihistamines – chlorphenamine 10mg IV and steroids – hydrocortisone 200mg IV
  6. Give fluid resuscitation: 500mL of 0.9% saline IV over 15 minutes is patient has signs of shock despite adrenaline
  7. if the patient has a wheeze, treat as per asthma (5mg salbutamol nebulisers)

Consider ITU admission if: still hypotensive, patient required 3 or more doses of adrenaline, severe bronchospasm during treatment, co-morbid

If ITU isn’t indicated admit to CDU (clinical decision unit) or similar

  • Start investigations
  • Continue chlorphenamine 4mg/6h PO if patient is still itching
  • Teach patient regarding self-administered adrenaline
  • Discharge with:

Two Epipens, 0.3mg
Prednisolone 40mg OD for 3 days
Chlorphenamine 4mg QDS or loratadine 10 mg OD for 3 days
Follow up in allergy clinic

Bedside Tests

ECG – non-specific ST changes are common post adrenaline with anaphylaxis

Laboratory Investigations

FBC, VBG

Special Investigations

Serum tryptase levels taken once emergency treatment has started with a second sample ½ hours after onset of symptoms
Normally undetectable (<1nanogram/mL)
Baseline level should be determined at least 24 hours after symptoms have resolved
Not necessary if the diagnosis is definite

Skin-prick tests to help identify antigens to avoid in the future

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