Fig. 1. Representative platelet aggregations. (A ) Aggregation curves induced by four concentrations of thrombin (0.005, 0.010, 0.015, and 0.020 U/ml). The ordinate represents the optical density, defined as 0% for platelet-rich plasma and 100% for platelet-poor plasma. The abscissa represents time (0–5 min). (B ) Aggregation curves induced by thrombin (0.01 U/ml). Samples were pretreated with halothane, isoflurane, or sevoflurane for 5 min. Concentrations for each anesthetic agent were 0.5, 1.0, and 1.5 mM. Both ordinate and abscissa are as in (A ).