Figure 61-9 Blood levels of fibrinopeptide A (FPA) in patients receiving saline (n = 25), 10 units/kg of intravenous unfractionated heparin (n = 25), or 20 units/kg of intravenous unfractionated heparin (n = 25) during hybrid total-hip replacement. Five blood samples were taken at specific times during surgery: sample 1, baseline, which was before the epidural injection; sample 2, immediately after insertion of the acetabulum; sample 3, 5 minutes after insertion of the femoral prosthesis; sample 4, 2 minutes after hip relocation; and sample 5, 30 minutes after surgery. Notice the increase in FPA in the saline group and the significant suppression in the groups receiving 10 units/kg or 20 units/kg during insertion of the femoral component. Values are given as the mean ± SEM. Asterisk, P = .0001 compared with 10 and 20 units/kg. (Adapted from Sharrock NE, Go G, Sulco TP, et al: Dose response of intravenous heparin on markers of thrombosis during primary total hip replacement. Anesthesiology 90:981–987, 1999.)