162 - Assessment of Beta-lactam Allergies as Rationale for Receipt of Vancomycin for Surgical Prophylaxis

Background: Beta-lactam (BL) antibiotics are first-line agents for most patients receiving antimicrobial prophylaxis in surgical procedures. Despite evidence showing low cross-reactivity between classes of BLs, patients with allergies commonly receive vancomycin as an alternative to avoid allergic reaction. The objective of this study was to identify potentially inappropriate use of vancomycin surgical prophylaxis among patients with reported BL allergies.

Methods: Adult patients (≥18 years) receiving vancomycin for surgical prophylaxis with a reported penicillin and/or cephalosporin allergy at our institution between August 2017 to July 2018 were retrospectively evaluated for potential eligibility for penicillin allergy testing and/or receipt of standard prophylaxis. Surgery type and allergy history were extracted from the electronic medical record. Per our institution’s penicillin-testing protocol, patients with IgE-mediated reactions < 10 years ago were eligible for penicillin skin testing (PST), mild reactions or IgE-mediated reaction > 10 years ago were eligible for direct oral amoxicillin challenge, and severe non-IgE mediated allergies were ineligible for penicillin allergy evaluation or BL prophylaxis.

Results: Among 830 patients who received vancomycin for surgical prophylaxis, 196 reported BL allergy and were included in the analysis (155 with penicillin allergy alone; 21 with cephalosporin allergy; 20 with both cephalosporin and penicillin allergy). Approximately 40% of surgeries were orthopedic. Six patients were ineligible for BL prophylaxis.  Per institutional protocol, 73 of 155 patients (48%) may have qualified for PST; 81 of 155 (52%) patients may have received a direct oral amoxicillin challenge.  Only 3 of 22 patients with history of methicillin-resistant Staphylococcus aureus appropriately received additional prophylaxis with vancomycin and a BL.

Conclusion: Patients with BL allergies often qualify for receipt of a first-line BL antibiotic. An opportunity exists for improved BL allergy assessment as an antimicrobial stewardship intervention. Future studies should evaluate outcomes associated with BL allergy evaluation and delabeling in patients receiving surgical prophylaxis.