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