The effect of tourniquet inflation on cefazolin tissue penetration during total knee arthroplasty

Patients undergoing total knee arthroplasty were randomized to tourniquet inflation 1, 2, or 5 minutes after a 1-g dose of cefazolin. Serum, soft tissue, and bone samples were obtained at 10, 30, and 60 minutes after inflation, immediately prior to tourniquet release (PTR), and 5 minutes after release. Areas under the concentration-time curve (AUC10-PTR) were calculated using the linear trapezoidal method and normalized to actual body weight, creatinine clearance, and length of tourniquet inflation. The percentage of penetration was calculated using the normalized values for the respective AUCs. Differences among the groups were analyzed using analysis of variance or the Kruskal-Wallis test where appropriate. Groups were similar for age, actual body weight, duration of tourniquet inflation, and creatinine clearance (p greater than 0.05). The median percentages of penetration for soft tissue and bone at 5, 2, and 1 minute were 14.5% and 4.6%, 6.7% and 3.0%, and 5.9% and 4.6%, respectively. Only the percentage of soft tissue penetration between 5 and 1 minute was significantly different (p = 0.015). Gender and type of anesthesia (general, epidural) had no effect on cefazolin penetration into soft tissue or bone. Although increasing the time interval between cefazolin administration and tourniquet inflation resulted in higher soft tissue drug concentrations, a 1-minute interval resulted in soft tissue and bone cefazolin concentrations at or above the minimum inhibitory concentration for microorganisms likely to be encountered in this surgical procedure.