D3.344 - Rapid Desensitization to Iohexol Following Iopamidol-Induced Anaphylaxis Prior to Urgent Coronary Angiography

Although the use of low-iodine, low-osmolar radiocontrast agents has reduced the incidence of contrast media–related hypersensitivity reactions, these reactions continue to occur at a rate of approximately 0.2%–0.7%. The risk of serious adverse effects remains significant, and approximately one death due to a severe adverse reaction is reported per 100,000 administrations. Desensitization protocols have been safely implemented in high-risk patients requiring urgent surgical or diagnostic procedures, as reported in the literature. We had to apply an urgent desensitization protocol successfully to a patient before coronary angiography who happened to have anaphylaxis in previous CT angiography due to iodinated contrast media.

A 62-year-old male patient underwent coronary CT angiography (Iopamidol) due to exertional dyspnea, a history of hyperlipidemia, and a family history of coronary artery disease. Approximately 30 minutes after contrast exposure, he presented to the emergency department with generalized erythema and a sensation of fainting. On examination, uvular edema, diffuse cutaneous erythema, and hypotension (65/40 mmHg) were noted. He was diagnosed with anaphylaxis and treated with 0.5 mg intramuscular epinephrine, 125 mg intravenous methylprednisolone, 1000 mL normal saline, and 45 mg intravenous pheniramine. Following complete resolution of clinical symptoms and stabilization of vital signs, the patient was observed for 24 hours and subsequently discharged in stable condition.

Upon detection of a 70% high-risk stenosis in the LAD on the coronary CT angiography report, urgent coronary angiography was planned, and the patient was evaluated in the adult allergy and clinical immunology clinic. No skin testing was performed due to his recent anaphylaxis and ongoing antihistamine therapy. An inpatient rapid desensitization protocol was planned immediately prior to coronary angiography using an alternative iodinated contrast agent (Iohexol 300 mg/100 mL).

Methylprednisolone 40 mg was administered 13, 7, and 1 hour prior, and pheniramine 45 mg was given 1 hour before the procedure, after which an 11-step rapid desensitization protocol was performed. The first ten steps were performed under monitoring in the ward, and the eleventh step was administered during the angiography procedure. No immediate hypersensitivity reactions were observed during the desensitization process or within 24 hours after coronary angiography. Therefore, the protocol was considered successful.