Successful Graded Dose Challenge to Iodixanol Radiocontrast Media in a Patient With Delayed Anaphylaxis to Iohexol

Case Report: A Rare Case of Iodixanol-Induced Anaphylactic Shock in Cerebral Angiography

Background

Adverse reactions induced by isoosmolar contrast medium (iodixanol) are mostly mild, with rashes and headaches being the most common. Although anaphylactic shock has been reported, no related incidents have been documented on cerebral angiography.

Objective

This article reports a serious case of anaphylactic shock possibly induced by iodixanol and provides an overview of the case report.

Case Summary

A 65-year-old female with persistent headaches for nearly six months and CTA examination revealed multiple intracranial aneurysms. After two treatments, she returned to the hospital for aneurysm of reexamination a month ago. Following a preoperative assessment, cerebral angiography was performed. Three minutes after the procedure, the patient experienced dizziness, increased heart rate, followed by hypotension (BP 90/43 mm Hg), a sudden drop-in heart rate (HR 68 bpm), and a drop in SpO2 to 92%. Intravenous dexamethasone for anti-allergic were administered immediately, along with therapy through oxygen-inhalation. However, the patient then developed limb convulsions, unresponsiveness, and was urgently given diazepam for sedation and sputum aspiration to maintain airway patency. Blood pressure decrease to 53/29 mm Hg, and SpO2 readings were unavailable. Intravenous dopamine to elevates blood pressure, and assists breathing by intubating in the endotracheal. After 3 minutes, as the blood pressure remained undetectable, intermittent intravenous epinephrine 1mg was administered to raise the blood pressure, gradually restoring it to 126/90 mm Hg, and SpO2 increased to 95%. The patient was diagnosed with iodixanol-induced anaphylactic shock and urgently transferred to the NICU for monitoring and treatment. The patient died despite immediate treatment.

Conclusion

A 65-year-old female developed serious anaphylactic shock during cerebral angiography after receiving iodixanol. Although iodixanol is considered one of the safest iodinated contrast mediums (ICM), clinicians should be aware of its the potential for serious hypersensitivity reactions that can lead to fatal and life-threatening events.

Successful Desensitization to the Radiocontrast Material Iohexol (Omnipaque™)

Adverse reactions to radiocontrast media (RCM) are rare and occur predominantly in association with intravenous administration but may also occur with intra-arterial and nonvascular injections (e.g., retrograde pyelography, intra-articular injections) of RCM. This article reports the case of a 52-year-old lady who was known to have amyloidosis secondary to rheumatoid arthritis and was on regular renal replacement therapy. She was under follow-up for regular angioplasties to manage the central vein stenosis that was affecting her right brachiocephalic arteriovenous fistula (AVF) and was referred to our Immunology service when she developed an allergic reaction after her AVF angioplasty (central venoplasty). Despite being dialysed immediately post-angioplasty, she complained of skin rash and itching with hoarseness of voice that developed almost six to eight hours post-angioplasty. We decided to arrange the iodinated non-ionic iso-osmolar contrast agent iodixanol (Visipaque™) for her instead, as it is known to be better tolerated in patients with reactions to Omnipaque™ due to its lower osmolarity as compared to Omnipaque™. However, since it was the first time to request this contrast in our hospital, it was not possible due to logistical reasons. It was necessary that our patient continued to undergo angioplasty every three months, however, she was developing more severe and earlier symptoms with each subsequent exposure to the radiocontrast medium. After her latest reaction of generalized itching and angioedema with shortness of breath during the procedure despite premedication, it was decided for her to undergo desensitization to Omnipaque™. In the absence of a published protocol for this, we used a protocol used for desensitization to Visipaque™. She showed an excellent response and completed her remaining angioplasties until Visipaque™ became available. Hence, desensitization to Omnipaque™ using the published protocol to Visipaque™ is likely to help patients allergic to Omnipaque™ or where Visipaque™ is not available or non-affordable in low/middle-income countries.

MRGPRX2 mediates immediate-type pseudo-allergic reactions induced by iodine-containing iohexol

BACKGROUND

Iohexol is a typical iodinated radiocontrast medium and widely used in clinical angiography. Hypersensitivity reactions induced by iohexol are common side effects known to increase the risk for patients. Iodine is the main functional group of iohexol, and it can induce delayed anaphylaxis. However, iohexol also induces immediate-type allergies, but the underlying mechanism is still not clear. MRGPRX2 is a key receptor present on mast cells, which mediates pseudo-allergic reactions induced by various drugs.

METHODS

We aimed to verify the relationship between iohexol-induced anaphylactic reactions and MRGPRX2. MRGPRX2-mediated pseudo-allergic reactions induced by iohexol were investigated in vivo and in vitro using a mouse model of local and systemic anaphylaxis and mast cell degranulation assays, respectively.

RESULTS

Iohexol caused pseudo-allergic reactions in wild-type (WT) mice by activating mast cells to release histamine and cytokines. However, it did not induce a similar phenomenon in Kit^W-sh/W-sh (MUT) mice. Iohexol stimulated intracellular calcium ion (Ca²⁺) influx in MRGPRX2-HEK293, MrgprB2-HEK293, and LAD2 cells but not in NC-HEK293 cells. After knockdown of MRGPRX2 expression in LAD2 cells, the degree of iohexol-induced degranulation was reduced. In addition, after structural modification of iohexol by removal of iodine, a reduction in iohexol-induced effects, such as local and systemic anaphylaxis in mice and degranulation of LAD2 cells, could be observed. Iohexol was shown to induce immediate-type pseudo-allergic reactions via MRGPRX2, which was dependent on the presence of iodine.

CONCLUSIONS

Conclusively, inhibition of MRGPRX2-mediated mast cell degranulation and cytokine release is important to prevent iohexol-induced immediate-type pseudo-allergic reactions.

The involvement of osmolarity in the safety of contrast media

Background

New non-ionic contrast agents, classified into low osmolar agents and iso-osmolar agents, present different biochemical characteristics that may influence the allergic reactions they cause. The aim of our study was to evaluate how osmolarity may affect safety in the use of contrast agents.

Case presentation

Six patients with a positive history for reaction to contrast agent were included in this study. Only one patient prick and intradermal skin test was positive. However, in 5 cases, patients presented an immediate reaction after administration of contrast agent that was not IgE mediated.

Conclusions

In this study, we focused on iodixanol, an iso-osmolar contrast agent, finding good safety of this product in patients with previous hypersensitivity reactions to contrast agent.