Antithrombin efficiency is maintained in vitro in human plasma following dilution with hydroxyethyl starches

Hemodilution has been associated with changes in hemostasis secondary to modulation of procoagulant activity. However, direct effects of specific fluids on anticoagulants, such as antithrombin (AT), remained undefined. Thus, the purpose of this investigation was to determine whether hemodilution with hydroxyethyl starches (HES) directly diminishes plasma AT activity, which would be manifested by decreases in clot initiation time (reaction time, R) with thrombelastography greater than that seen with 0.9% NaCl (NS). Normal plasma and AT-deficient (< 1 % activity) plasma were diluted 0 or 30% with NS, Hextend (6% HES; average molecular weight, 450 kDa), PentaLyte (6% HES; average molecular weight, 220 kDa), or Voluven (6% HES; average molecular weight, 130 kDa) (n = 6-7 experiments per condition). Undiluted, normal plasma had an R value of 796 +/- 65 s, which was significantly (P < 0.05) greater than R values following NS (690 +/- 50 s) or Voluven (675 +/- 68 s) dilution. R values of normal plasma diluted with Hextend (831 +/- 51 s) or PentaLyte (801 +/- 72 s) were not different from undiluted plasma but were significantly (P < 0.05) greater than those observed following NS or Voluven dilution. There were no significant differences between the conditions when AT-deficient plasma was utilized (R range, 404-440 s). Rather than interfere with AT activity, HES with an average molecular weight of 220-450 kDa maintain AT efficiency.