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 eff ect of intraoperative and postoperative blood loss during spinal surge ry on serum cefazolin level. Objectives. To determine what effect, if any, intraoperative blood loss has on serum antibiotic levels, and to determine ii 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 spina l fusion with internal fixation is significant. It commonly has been a ccepted that blood loss results in a more rapid clearance of antibioti c. Methods. Nineteen patients scheduled for elective spinal fusion wit h internal fixation were enrolled in this study. Each patient served a s his or her own control. Baseline cefazolin clearance was determined the week before surgery. Cefazolin clearance again was determined intr aoperatively. Blood loss was recorded throughout the procedure. Result s. The mean blood loss was 650 mL. There was no significant difference between preoperative and intraoperative cefazolin clearance, and ther e was no correlation between blood loss and cefazolin level. Conclusio ns. It is not necessary to give cefazolin at a dosing interval of less than 4 hours with blood losses of up to 1200 mL. This will maintain t he antibiotic concentration well above the minimum inhibitory concentr ation.