Background: Individuals with type O blood have reduced factor VIII and von Willebrand factor levels compared to the non-O counterpart. Infusion of hydroxyethyl starch (HES) impairs coagulation and, in O blood type, apparent coagulopathy can develop after HES infusion. A newly market-released balanced HES (670/0.75) has physiologic pH and balanced electrolytes including calcium, which are beneficial to coagulation. Studies comparing balanced HES (670/0.75) with saline-based HES (130/0.4), previously known the least coagulopathic are rare. Therefore, we try to reveal the difference of coagulation, pH/electrolyte balance, and bleeding amount between the non-O and O blood types after infusion of these two newest HES.

Methods: Each 20 of non-O and type O ASA 1 or 2 patients scheduled for spinal surgery involving 2 or 3 spinal levels were enrolled. 20 ml/kg of saline-based HES (130/0.4) or balanced HES (670/0.75) was administered during operation. Blood loss, coagulation and metabolic profiles were checked at pre-infusion (T0), 5 min after infusion (T1), 4 hrs after infusion (T2) and 24 hrs after infusion (T4).

Inclusion Criteria:

• Patients of ASA 1 or 2, and scheduled for posterior laminectomy and internal fixation at two or three spinal levels.

Exclusion Criteria:

• the presence of cardiovascular diseases, cerebral vascular disease, hepatic, pulmonary, or renal disease, hemoglobin < 12 g/dl, platelet count < 150,000 /ml, coagulopathy, taking medication likely to alter coagulation less than 2 weeks before the study, or an allergic reaction to HES