Chlorhexidine Tomaz Garcez Consultant Immunology

What we already know (1) Chlorhexidine is widely used in healthcare and the community (see appendix in report) A “hidden allergen” responsible for a significant number of cases of perioperative anaphylaxis Geographical variation Under-recognition Differential practice / use of decontamination / testing for allergy Highly effective antiseptic

What we already know (2) Uses include: Skin decontamination Lubricating gels Coated catheters (CVC) Dental Commonly there are features of a prior reaction in those subsequently confirmed with allergy Investigation for allergy not standardised (timing or tests) Positive tests to other potential culprits reported

Key Findings (1) 3rd of the “big four” – 18 cases (9%) 16 males 6 urology surgery; 3 cardiac; 3 orthopaedics 0.78 events per 100,000 exposures (possible overestimate) 1 fatal case Not investigated by specific IgE to chlorhexidine

Exposure routes Number Time to onset & grade Skin for cannula 10 Skin for neuraxial blockade 7 Skin for surgical site 4 ≈ 1 hour; grade 3 Coated CVC 6 < 5 minutes; grade 4 Urethral gel 11 None where only reported exposure was skin preparation for cannulation

Clinical features

Key Findings (2) Often not suspected (only in 28% of cases) by anaesthetist 3 potentially avoidable cases 1 reported prior chlorhexidine allergy 1 reported prior perioperative allergy that was not investigated 1 NAP6 confirmed chlorhexidine allergy case experienced subsequent anaphylaxis to chlorhexidine in 2nd procedure Chlorhexidine coated central lines not always removed (2 of 6 CVC related cases)

Key Findings (3) 16 patients had dynamic / raised tryptase Testing for chlorhexidine was frequently omitted in allergy clinics Testing does not always follow recommendations

Test modalities Number Positive* Skin prick testing only 7 6 Skin prick testing and IgE 3 3 (both tests) Skin prick testing, intradermal testing and IgE 2 (all tests) 1 (IDT & IgE) IgE only 2 Intradermal testing only 1 Intradermal testing and IgE 1 (both tests) Only 7 cases had more than one test as is recommended In 3 cases more than one trigger identified on testing

Key Recommendations National: Institutional: Individual: Prominent labelling (MHRA & manufacturers) Institutional: Alternatives should be available All cases should be tested for chlorhexidine with at least 2 modalities of test; and all potential culprits should be tested Individual: Improved awareness of chlorhexidine and allergy history taking Chlorhexidine coated CVCs should be removed when anaphylaxis occurs following insertion

Thank you