Allergy

Last Updated on by frcemuser

Allergic Reaction

  • IgE mediated mast cell degranulation and histamine release as in urticaria
  • Type I hypersensitivity

Urticaria Treatment In ED:

  • identify the cause and trigger – avoidable cause and trigger
  • Non-sedating antihistamine – Cetrizine , loratadine, fexofanadine
  • if severe add steroids oral – Prednisolone  40mg

Allergic Angioedema

  • IgE mediated
  • urticaria with swelling of deeper dermal, subcutaneous, and submucosal tissues, often affecting the face (lips, tongue, and eyelids), genitalia, hands, or feet
  • 1-2 hours after exposure to allergens

Anaphylaxis – Allergic

Definition -Acute Onset of Symptoms – Life-Threatening Airway/Breathing/Circulation Problems

Airway — hoarse voice, stridor, throat “closing up” and tongue swelling, drooling
Breathing – SOB, tachypnoea, wheeze, hypoxia, cyanosis
Circulation — tachycardia, hypotension, shack and decreased conscious level
Rash — generalised urticaria Or angioedema

Adrenaline.

  • IM doses of 1:1000 adrenaline
  • Adrenaline should be given again after 5 minutes until an adequate response
  • Titrate IV adrenaline Adult – 50 microgram / 1 microgram/kg Children ) ( by experienced person )

Fluids.

  • crystalloid 20 mL/kg in a child or 500 – 1000 mL in an adult

Steroids and anti-histamines 2nd line

  • Chlorphenamine 10mg IV (adult dose)
  • Hydrocortisone 200mg IV (adult dose)

Other Drugs

  •  Glucagon can be useful to treat an anaphylactic reaction in a patient taking a beta-blocker.
  • Asthma – consider further bronchodilator therapy with salbutamol, ipratropium, aminophylline or magnesium
Age Group IM Adrenaline (1:1000) IM/IV Chlorphenamine IM/IV Hydrocortisone
Adult 500 mcg (0.5 mL) 10 mg 200 mg
Child > 12 years 500 mcg (0.5 mL) 10 mg 200 mg
Child 6 – 12 years 300 mcg (0.3 mL) 5 mg 100 mg
Child 6 months – 6 years 150 mcg (0.15 mL) 2.5 mg 50 mg
Child < 6 months 150 mcg (0.15 mL) 250 mcg/kg 25 mg

Mast Cell Tryptase

  • Serum Mast Cell Tryptase (0 hours, 2 hours later and 24-hour sample)

Discharge

  • Patients should be observed for at least 6 hours
  • with Safety Net, Biphasic Reaction Risk,
  • 3 days of Antihistamine/Steroids

Non-allergic angioedema

  • bradykinin mediated
  • angioedema without urticaria, a non-allergic cause is likely
  • It often does not respond to treatment with adrenaline, antihistamines and corticosteroids.

Drug-Induced

  • Occurs days to months after taking the eliciting drug (ACE inhibitors )

Hereditary angioedema (HAE)

  • Autosomal dominant
  • C1-esterase-inhibitor deficiency

Acquired angioedema (AAE)

  • Acquired C1-esterase-inhibitor deficiency, usually secondary to lymphoma or connective tissue disorder e.g. SLE

Idiopathic angioedema

  • Usually a chronic and relapsing angioedema with an unknown cause

Treatment non-allergic Angioedema

  • Icatibant (a bradykinin B2receptor antagonist) or C1 esterase inhibitor concentrate (fresh frozen plasma).
Allergic Angioedema Non-Allergic Angioedema Anaphylaxis
  • Anatomically localised attack
  • Acute onset
  • Urticaria
  • Pruritus
  • Normotension
  • Anatomically localised attack
  • Gradual onset
  • No pruritus
  • Previous identical episodes
  • Abdominal pain
  • Normotension
  • Systemic symptoms
  • Rapid onset and progression
  • Respiratory failure
  • Cardiovascular collapse

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