D1.39 - Differential Diagnosis of Perioperative Anaphylaxis: The Hidden Role of Chlorhexidine

Perioperative anaphylaxis is a rare but potentially fatal reaction. Muscle relaxants and antibiotics are the most common causes. However, chlorhexidine is an emerging etiology in these types of reactions.

Nevertheless, it is an underdiagnosed cause not only in surgical settings but also in any procedure where it is increasingly used as an antiseptic. This case describes the differential diagnosis of an anaphylactic reaction.

A 72-year-old male developed generalized hives and hypotension immediately after the start of catheterization with iodinated contrast. Adrenaline, corticosteroids, antihistamines, and ranitidine were administered, leading to progressive resolution of the symptoms. A blood sample taken during the acute phase showed a tryptase level of 62.9 μg/L.The patient was subsequently referred to the allergology department, where a detailed medical history was obtained. All agents and medications during the procedure were reviewed, including mepivacaine, nitroglycerin, sodium heparin and iodinated contrast Iopamidol, followed by the corresponding allergological study.

Skin tests:

- Prick and intradermal tests for iodinated contrast agents Visipaque® (iodixanol), Iopamiro® (iopamidol), Iomeron® (iomeprol), and Plenigraf® (sodium amidotrizoate, meglumine amidotrizoate, and calcium amidotrizoate), as well as mepivacaine, nitroglycerin, and sodium heparin: negative.

- Prick test with aqueous chlorhexidine 0,5%: positive.

Basophil activation test for the mentioned iodinated contrasts: negative.

Blood analysis:

- Basal tryptase: 7.76 μg/L.

- Total IgE 514 kU/L.

- Elevated specific IgE to chlorhexidine: 2.57 kU/L.

Upon further inquiry, the use of chlorhexidine for asepsis before injecting the iodinated contrast was confirmed.

Following the study, a new coronary angiography was performed using iodixanol as the iodinated contrast agent without using chlorhexidine, with the patient showing good tolerance.

We present a patient with suspected allergy to iodinated contrasts, that finally was diagnosed with chlorhexidine-induced anaphylaxis based on positive skin tests and specific IgE results for this antiseptic. However, we were unable to exclude an allergy to iopamidol as the exposure test was not performed. Good tolerance to the iodinated contrast iodixanol was demonstrated.

With this case, we highlight the importance of identifying all potentially used agents and medications, such as chlorhexidine, and conducting an allergy workup to determine the cause, avoid misdiagnoses, and minimize unnecessary risks.