Editor's Spotlight/Take 5: Vancomycin Prophylaxis for Total Joint Arthroplasty: Incorrectly Dosed and Has a Higher Rate of Periprosthetic Infection Than Cefazolin

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Weight-based dosing of medications is not a foreign concept to most of us. We learned it in medical school, especially while rotating on the pediatrics service. We did it while in residency, ordering weight-based gentamicin for certain open fractures [10]. And when we order antibiotics for treatment, we sometimes adjust the dose to ensure therapeutic dosing. But for prophylactic antibiotics before surgery, somehow the fixed 1-g dose has become common practice. Most patients receive a 1-g dose of cefazolin, and for those patients with a beta-lactam allergy, 1-g dose of vancomycin is sometimes substituted. But patients come in different sizes.
There is good evidence suggesting that failing to recognize this may increase the risk of prosthetic joint infection (PJI). A recent study [21] looking at trabecular bone harvested from patients who underwent TKA demonstrated that vancomycin levels in bone varied with BMI, where higher concentrations were seen in patients with lower BMI. Additionally, the study points to the pharmacokinetic properties of vancomycin, where it has greater deposition in soft tissues when compared to cefazolin; therefore, a smaller proportion of vancomycin is available in trabecular bone. Surgeons may use vancomycin for prophylaxis in patients colonized with methicillin-resistant Staphylococcus aureus (MRSA), and this practice may become more widespread as the prevalence of MRSA infection is increasing [9, 19]. However, we sometimes use vancomycin for patients with a history of penicillin allergy, a practice that perhaps should be abandoned. There is, in fact, little risk that a patient with a reported allergy to penicillin will experience anaphylaxis when given cefazolin [3, 14].
The question we are most concerned about, though, is whether patients are adequately dosed with whatever antibiotic they do receive, and whether those who are underdosed are more likely to develop PJI, which is a dreaded complication. In this context, the work of Dr. Kheir and his team from Thomas Jefferson University in Philadelphia, PA, USA should matter to all orthopaedic surgeons. They found that among primary TJAs, patients receiving vancomycin had a higher rate of PJI compared with patients receiving cefazolin prophylaxis, and that the majority of patients given vancomycin prophylaxis were underdosed based on the weight-based dosage recommendations. In a glimmer of bright news, MRSA did not occur in patients who were adequately dosed with vancomycin. In addition to adequate dosing, this paper gives us an important reminder that surgeons should use vancomycin judiciously and rarely as a sole agent. Please join me for the Take-5 interview with Dr. Michael M. Kheir, as we dig deeper into this critically important clinical problem.
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