Serum cefazolin levels during spinal fusion: effect of blood loss and duration of surgery.

Perioperative cefazolin prophylaxis is commonly employed in posterior spinal fusion (PSF) procedures, which are often lengthy and involve significant blood loss. In this study, serum levels of prophylactically administered cefazolin were measured serially during spinal fusion procedures, and the possible relationship of antibiotic concentrations to blood loss and fluid therapy were examined. Serum antibiotic levels, measured at 30-min intervals, declined with a half-life of 90 min, similar to the previously reported experience with normal adult volunteers. There was no relationship between serum half-life and blood loss or fluid replacement. An explanation for these findings is offered, along with recommendations for dosing.