Weighing in on antibiotic dosing for surgical site prophylaxis

Extract

In an article in this issue of AJHP, Morris and colleagues¹ highlight the importance of proper dosing of prophylactic antimicrobials, especially in higher-body-weight individuals undergoing knee or hip arthroplasty. In their large cohort of patients in New Zealand, the authors showed an increased risk of development of a surgical site infection (SSI) among patients who were underdosed with cefazolin. While this was not the first study to highlight the need for larger antibiotic doses for surgical prophylaxis in patients with higher body weights, Morris and colleagues demonstrated the complications and increased cost that can occur with underdosing.

In the study, the recommended first-line therapy for prophylaxis for knee and hip arthroplasty was cefazolin or cefuroxime; that was based upon local guidelines but mirrored other guidelines.^2,3 What is unclear (and pointed out in the article) is why there remains disagreement among different guidelines on the issue of giving larger antibiotic doses to patients with higher body weights. Additionally, what is the exact weight that we should consider for someone to be classified as a higher body weight individual: >120 kg, >140 kg, or, alternatively, a body mass index (BMI) threshold value?