FIRST-TIME EVALUATION OF INTRA- AND POSTOPERATIVE CEFUROXIME TARGET SPINE TISSUE CONCENTRATIONS IN LONG-LASTING SPINE SURGERY FOLLOWING REPEATED WEIGHT-DOSED INTRAVENOUS ADMINISTRATIONS

Aim Antibiotic prophylaxis is central in preventing postoperative spine infections, yet knowledge of clinical spine tissue antibiotic concentrations remains limited. Pooled postoperative spine infection rates are constant (approximately 3%), resulting in severe patient morbidity, mortality, and prolonged hospitalization. Current antibiotic dosing regimens often involve fixed doses based on empirical knowledge, surrogate measures (plasma samples), non-clinical evidence (experimental models), and inferior methodology (tissue specimens). Therefore, personalized antibiotic dosing may be the future of antibiotic prophylaxis to prevent postoperative infections, especially implant infections. The aim was to continuously evaluate intra- and postoperative cefuroxime target spine tissue concentrations in long-lasting spine surgery after personalized dosing by repeated weight-dosed intravenous administrations. Method Twenty patients (15 female, 5 male) scheduled for long-lasting spine deformity surgery with hypotensive anaesthesia were included; median age (range): 17.5 years (12-74), mean BMI (range): 22.2 (16.2-37.7), and mean surgery time (range): 4h 49min (3h 57min-6h 9min). Weight-dosed cefuroxime (20 mg/kg) was administered intravenously to all patients on average 25 min before incision and repeated after 4 hours. Microdialysis catheters were placed for sampling of cefuroxime concentrations in vertebral bone (only intraoperative sampling), paravertebral muscle, and subcutaneous tissue as soon as possible after surgery start. Upon wound closure, two additional catheters were placed in the profound and superficial part of the wound. Microdialysis and plasma samples were obtained continuously intra- and postoperative for up to 12 hours. The primary endpoint was (based on cefuroxime time-dependent efficacy) the time with cefuroxime concentrations above the clinical breakpoint minimal inhibitory concentration for Staphylococcus aureus of 4 µg/mL in percentage (% f T>MIC4) of patients’ individual surgery time, first dosing interval (0-4 hours), second dosing interval (4-12 hours). Results Mean cefuroxime % f T>MIC4 (range) of: patients’ individual surgery time was 100% (100-100%) in all investigated tissues. the first dosing interval was 93% (93-93%) in vertebral bone, paravertebral muscle, subcutaneous tissue, and 99% (99-100%) in plasma. the second dosing interval was 87% (52-100%) in paravertebral muscle, 89% (52-100%) in subcutaneous tissue, 91% (71-100%) in the profound wound, 94% (72-100%) in the superficial wound, and 71% (42-100%) in plasma. Conclusions Personalized cefuroxime dosing by repeated weight-dosed (20 mg/kg) intravenous administrations provided homogenous and therapeutic spine tissue exposure across all investigated tissues and plasma in long-lasting spine surgery with hypotensive anaesthesia (up to 11 hours). Thus, personalized cefuroxime dosing may decrease the risk of postoperative spine infection, especially in cases with implant insertion.