Perioperative Administration of Antimicrobials During Tibial Plateau Leveling Osteotomy Alim Nazarali 1 , Bsc, Ameet Singh 1 , DVM, DVSc, Diplomate ACVS, and J. Scott Weese 2 , DVM, DVSc, Diplomate ACVIM 1 Department of Clinical Studies, and 2 Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Canada Corresponding Author Dr. Ameet Singh, DVM, DVSc, Diplomate ACVS, Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada. E‐mail: amsingh@uoguelph.ca Submitted July 2013 Accepted December 2013 DOI:10.1111/j.1532-950X.2014.12269.x Objective: To evaluate perioperative antimicrobial administration during tibial plateau leveling osteotomy (TPLO) in dogs at the Ontario Veterinary College Health Sciences Centre. Study Design: Retrospective case series. Animals: Dogs (n ¼ 184) that had TPLO (n ¼ 226). Methods: Medical records were reviewed and data collected included timing and dosage of pre, intra, and postoperative antimicrobial administration, method of stifle inspection, duration of surgery, duration of anesthesia, development of surgical site infection (SSI), microbiological investigation, implant removal, and possible comorbidities. Univariable analysis was conducted, followed by stepwise forward logistic regression to determine factors associated with SSI. Results: Of the 225 cases administered perioperative antimicrobials, 96 (42.5%) received appropriate perioperative antimicrobial prophylaxis based on target times for preoperative and intraoperative dosing. Postoperative antimicrobials were administered to 54 (23.9%) of cases. Surgical site infection was documented in 30 (13.3%) cases. Staphylococcus pseudintermedius was isolated from 15/17 (88.2%) SSI from which a bacterium was isolated, with 6/15 (40%) being methicillin‐resistant Staphylococcus pseudintermedius (MRSP). Postoperative administration of antimicrobials was protective for SSI (OR 0.1367; P ¼.0001; 95% CI ¼ 0.021, 0.50). Duration of anesthesia time was associated with the likelihood of development of SSI (OR ¼ 1.0094; P ¼.001; 95% CI ¼ 1.00, 1.02). Conclusion: Current practices for administration of antimicrobial prophylaxis during TPLO can be improved. There was no association between timing of antibiotic administration that was inconsistent with the target and development of SSI. Further study into risk factors of TPLO SSI is required. Tibial plateau leveling osteotomy (TPLO) is one of the most commonly performed surgical techniques to stabilize a cranial cruciate insufficient stifle in dogs. 1 Despite being classified as a clean surgical procedure, TPLO has been associated with increased risk of surgical site infection (SSI) compared to other clean procedures, with incidences ranging from 0.8–14.3%. 2–9 Reasons for the apparently high rate of TPLO SSI are unclear and likely multifactorial. Potential factors include thermal damage by the saw blade used to perform the osteotomy, minimal soft‐tissue coverage of the proximal aspect of the tibia, excessive soft tissue dissection at surgery, presence of an implant, aggressive periosteal dissection, prolonged surgery and anesthesia times, periosteal compression by the implant and increasing prevalence of opportunistic pathogens (particu- larly staphylococci) that are resistant to antimicrobials used for perioperative prophylaxis. 6–11 Whereas there are no accepted standards, perioperative prophylaxis is commonly used with TPLO and has been considered as a treatment to minimize SSI. Various factors affect the potential efficacy of antimicro- bial prophylaxis. One is timing of administration, an area that receives major emphasis in human surgery. 12–14 The primary goal of antimicrobial prophylaxis is to have therapeutic levels present before incision and maintained throughout the surgical procedure. Standard recommendations from human medicine are to administer an appropriately selected antimicrobial at a maximum of 1 hour before first incision and then to discontinue the use of antimicrobials within 24 hours after procedure completion. 12 To maintain therapeutic levels during surgery, time‐dependent antimicrobials such as beta‐lactams are redosed intraoperatively every 2 half‐lives. 12 Similar guidelines are not available for veterinary surgery yet the concepts of antimicrobial prophylaxis should apply equally across species. However, there has also been limited scrutiny of current perioperative antimicrobial prophylaxis practices performed in small animal surgery within the veterinary literature 15,16 and none specifically directed at Veterinary Surgery 9999 (2014) 1–6 © Copyright 2014 by The American College of Veterinary Surgeons 1