272. Timing of preoperative surgical antibiotic prophylaxis prior to one- to three-level elective lumbar fusion

Abstract

BACKGROUND CONTEXT Surgical site infections (SSIs) in patients who have undergone lumbar fusion surgery can be a devastating complication and a common indication for revision surgery. The functional decline and economic burden put on the patient as a result of infection can drastically affect postoperative outcomes. As such, studies have identified potential areas of intervention, including: optimizing patient comorbidities, thoroughly supervising the operating room, and administering antibiotic prophylaxis. Guidelines have established a goal to infuse antibiotics within one hour prior to incision. PURPOSE The aim of this study was to examine the relationship between timing of preoperative surgical antibiotic prophylaxis and adverse outcomes (e.g. SSIs, 90-day readmissions, and revision surgery) with subgroup analysis stratified by type of antibiotic. While most antibiotics are administered within one hour of surgery, certain circumstances (ie, prolonged case duration, long operating room turnover) may delay the time from antibiotic administration to incision. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE A cohort of patients status post elective one- to three-level lumbar fusion performed between January 2013 and December 2018 was identified at a single, high-volume academic medical center using a database query via Standardized Query Language (SQL). OUTCOME MEASURES The primary outcome of interest was surgical site infections (SSIs), with secondary outcomes of interest including: 90-day readmission and revision surgery. METHODS SQL query and electronic medical record (EMR) chart reviews were used to identify patient demographics, surgical case characteristics, and postoperative complications. Patients were allocated into 5 groups based on the time period from preoperative antibiotic administration to incision (Group A = 0-15 min, Group B = 16-30 min, Group C = 31-45 min, Group D = 46 – 60 min, and Group E = 61+ min). SSIs were identified by the definition set forth by the CDC. Statistical analysis, including a logistic regression model, was used to examine the relationship between patient/case characteristics, preoperative antibiotic timing, and postoperative outcomes. RESULTS From 1,131 patients included in the final analysis, 26 SSIs were identified. Univariate analysis revealed patients in Group E had significantly longer lengths of operation (p: 0.044) and higher mean comorbidity scores (p: 0.012) compared to all other groups. Logistic regression analysis revealed that Group E patients were 1.4 times more likely to develop an SSI and 7.2 times more likely to be readmitted within 90 days compared to Group A. Furthermore, Groups B-D did not show evidence of significantly higher odds of infection compared to Group A. When stratified by antibiotic type, patients treated with Vancomycin showed the lowest incidence of SSI when administered between 16-30 minutes, however Cefazolin showed the lowest incidence when administered between 0-15 minutes. Among 26 SSIs, nine cultures showed evidence of multi-drug resistance, with two treated preoperatively with vancomycin and seven treated with cefazolin. CONCLUSIONS Our results present that preoperative antibiotic administration beyond one hour in patients who have undergone lumbar fusion is associated with higher rates of SSI. Furthermore, the utility of vancomycin to minimize the risk of SSI is optimal when administered between 16 and 30 minutes prior to incision. An effective antibiotic prophylaxis regiment depends on patient characteristics and the pharmacokinetics of antibiotic selection, while minimizing side effects and multi-drug resistant organisms. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.