The effect of intraoperative blood loss on serum cefazolin level in patients undergoing instrumented spinal fusion: A prospective, controlled study

Study Design. This study is a prospective, controlled study of the effect of intraoperative and postoperative blood loss during spinal surgery on serum cefazolin level. Objectives. To determine what effect, if any, intraoperative blood loss has on serum antibiotic levels, and to determine if adjustment of the dose or dose interval is appropriate in operative cases of significant blood loss. Summary of Background Data. The problem of infection at the operative site after posterior spinal fusion with internal fixation is significant. It commonly has been accepted that blood loss results in a more rapid clearance of antibiotic. Methods. Nineteen patients scheduled for elective spinal fusion with internal fixation were enrolled in this study. Each patient served as his or her own control. Baseline cefazolin clearance was determined the week before surgery. Cefazolin clearance again was determined intraoperatively. Blood loss was recorded throughout the procedure. Results. The mean blood loss was 650 mL. There was no significant difference between preoperative and intraoperative cefazolin clearance, and there was no correlation between blood loss and cefazolin level. Conclusions. It is not necessary to give cefazolin at e dosing interval of less than 4 hours with blood losses of up to 1200 mL. This will maintain the antibiotic concentration well above the minimum inhibitory concentration.