Obictive:To evaluate the influences of preoperative acute hypervolemic hemodilution (AHHD) with 6% medium molecular Hydroxyethl startch(HES 200/0.5) on the activity of coagulation.

• 目的 :观察 6%25羟乙基淀粉 (贺斯 ；HES 2 0 0 / 0 .；5 )为容量扩充剂行术前急性高容血液稀释 (AHHD)对凝血功能的影响。