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Department of Anesthesiology, Critical Care Medicine, Pain Management, and Hyperbaric Medicine, Englewood Hospital, Englewood, NJ, aryeh.shander{at}ehmc.com
To the Editor:
Arellano et al. (1) compared hydroxyethyl starch (HES) 264/0.45 (Pentaspan®; Bristol-Myers Squibb, St. Laurent, Quebec) to 5% albumin in major reconstructive surgery and raised some interesting points. The authors' well-designed trial falls short because of inherent flaws and skewed randomization. As such, evidence regarding HES and its clinical effect on bleeding is inconclusive.
The effects of HES on platelets, factor VIII activity, and von Willebrand factor are well-defined in vivo (2–4). This study showed a dose-related significant prolongation of activated partial thromboplastin time, international normalized ratio, and reduction in von Willebrand factor A, von Willebrand factor L, and factor VIII activity in the HES group. The poor predictability of these tests for surgical bleeding has been established (5–7). Estimated blood loss and correlation between the worst test results and blood loss or transfusion were absent. No patient required re-exploration for microvascular coagulopathy. Thrombin time, which is negatively affected by albumin, was not assayed for or reported (8,9).
The demographic imbalances between the two groups may explain the increased transfusion rate in the HES group. The larger number of women in the HES group (58% versus 17%; P = 0.003) accounted for the differences in weight (P = 0.0003) and height (P = 0.02) between the groups. Smaller body mass and smaller blood volumes lead to higher transfusion rates. A larger sample could eliminate the gender and transfusion difference. The HES group received 15% more colloid (P = 0.003) and 20 mL/kg more of crystalloid (P = 0.12). This further dilutes clotting factors and increases activated partial thromboplastin time and international normalized ratio. Finally, estimated blood loss and the amount of transfused blood products were not reported.
The concern regarding the effect of starches on coagulation remains in question. The thought that coagulopathy from HES led to bleeding is difficult to conclude from this article. In vitro assessment of both albumin and starch show prolongation of clotting parameters but the clinical impact is unclear. Finally, transfusion of blood products is not an accurate measure of bleeding (10,11). As more information on the effects of colloids on coagulation accrues, condemnation of one product or another based on questionable evidence reduces the limited repertoire of fluids to be used for intravascular volume resuscitation.
References
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