Radiocontrast Media Allergy and Pretreatment
Pseudoallergic ...
245
Description

Radiocontrast Media Allergy and Pretreatment

Pseudoallergic (Anaphylactoid) Reaction

 • Pathogenesis - RCM directly stimulates mast cells / basophils

 • Epidemiology - 1-3% patients with ionic RCM & 0.5% pts w/ non-ionic RCM.

     - Severe rxns occur in 0.22% for ionic RCM, 0.04% for non-ionic RCM

     - Risk Factors: female, asthma, hx of previous anaphylactoid rxn to RCM, BB exposure, CV disease

 • Presentation: Immediate pruritus, urticaria, angioedema, airway obstruction, HoTN, abdominal pain

 • No evidence that iodine levels in seafood or topical solutions are related to adverse events from RCM; Seafood allergy is not a contraindication to RCM. Oral contrast is NOT contraindicated in a patient with IV contrast allergy, though rarely can cause a reaction

Pre-Treatment: 

 • Elective (13 h protocol)

    - Prednisone 50 mg PO @ 13, 7, & 1 h prior AND

    - Diphenhydramine 50 mg PO 1 h prior

 • Accelerated (4-5 h protocol)

    - Methylprednisolone 40 mg IV now & q 4 until scan AND

    - Diphenhydramine 50 mg IV 1h prior

 • Emergent

    - Methylprednisolone 40 mg IV 1 h prior AND

    - Diphenhydramine 50 mg IV 1h prior

 • Use low/isoosmolar RCM when possible

Delayed Reaction

 • Pathogenesis - T cell mediated 

 • Epidemiology: 2% of patients 

 • Presentation: >1 hr -1 week

    - Usually mild, skin eruption

    - Rare: SJS, TEN

 • Treatment: Supportive care



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