The Safety of Hydroxyethyl Starch (HES) – Products Now in Doubt

Ehab Farag, MD, FRCA; D. John Doyle, MD, PhD

To the Editor

Hydroxyethyl starch (HES) products are commonly employed for volume resuscitation in the perioperative period as well as in ICU patients being treated for sepsis and other conditions. The rationale for their clinical use is that they are low-cost colloids that are highly effective for increasing intravascular volume for sustained periods.1,2 Additionally, they are believed to have anti-inflammatory properties as well as other desirable characteristics, such as having a smaller impact on tissue edema compared to commonly used crystalloids.3 As a consequence, HES products have seen a great upswing in popularity in recent years, a fact no doubt also supported by a growing number of publications offering a favorable assessment of HES products.

The purpose of this short commentary is to draw attention to some recent safety concerns for HES products. While worries about the possibility of impaired blood clotting have been a concern for some time (vide infra), more recent studies suggest that HES products are also associated with acute renal injury as well as other adverse events, including an increase in mortality. The pathophysiology may be related to the fact that HES products, while undoubtedly effective at increasing plasma volume, do not stay localized to the circulation but end up instead as deposits in renal, hepatic, splenic, endothelial, and other tissues.4 In addition, as discussed later, HES molecules may interact with the endothelial glycocalyx in an unfavorable manner.

Evidence of the potential harm of HES products was in part diluted by a number of relatively favorable studies authored by Boldt et al., a great many of which turned out to involve scientific misconduct.5,6 This and other considerations have led to investigators to reconsider the role of HES products, as outlined below.

A consensus statement of the European Society of Intensive Care Medicine task force on colloid use in critically ill patients, has now recommended against the use of 6% HES 130/0.4 in ICU patients.7 Similarly, a 2011 Cochrane review cautioned against the routine administration of HES products.8 A systematic review by Hartog et al.9 concluded that, “There is no convincing evidence that third-generation HES 130/0.4 is safe in surgical, emergency, or intensive care patients despite publication of numerous clinical studies.” The recently published 7000 patient Crystalloid versus Hydroxyethyl Starch Trial (CHEST)10 showed that while there was no significant difference in 90-day mortality, patients randomized to HES 130/.4 had more renal injury and requirement for renal-replacement therapy than those receiving saline. Finally, a 2013 meta-analysis published in JAMA.11 noted that after 7 tainted HES studies by Boldt et al. were removed from consideration, “Hydroxyethyl starch was associated with a significant increased risk of mortality and acute kidney injury” and warned that the “use of hydroxyethyl starch for acute volume resuscitation is not warranted due to serious safety concerns.”

Although it has been known for some time that HES products can affect coagulation via adverse effects on both von Willebrand factor and platelet aggregation,12 it is now also known that HES 130/.4 administration results in a weaker, smaller clot.13 These facts may explain the increased transfusion rate in HES 130/.4 treated individuals with blunt trauma compared to those treated with normal saline.14

Finally, we would like to comment on the importance of the endothelial glycocalyx in understanding the effects of fluid administration. The endothelial glycocalyx covers the endothelial cells present in the lumen of normal blood vessels, playing a central role in its barrier properties. In conjunction with bound fluid and plasma proteins the glycocalyx forms an “endothelial surface layer,” typically 500 to 1000 nm thick. The bound proteins provide the endothelial surface layer with its own colloid osmotic force, with the consequence that Starling’s classic model (of semi-permeable capillaries subject to hydrostatic and oncotic pressure differences) is now considered to be an oversimplification.15,16

The glycocalyx harbors a wide variety of anticoagulant proteins like antithrombin, components of the protein C system, and tissue factor pathway inhibitors.17 The glycocalyx also plays a vital role in nitric oxide release in endothelial cells as well as modulating the immune response by preventing the adhesion of leucocytes and platelets to the endothelial cells.17,18 Damage of the glycocalyx can lead to protein extravasation and tissue edema as well as impair the processes mentioned above. Continuing research on the properties of the glycocalyx and endothelial surface layer is expected to yield a better understanding of the biology of vascular permeability, inflammatory processes, blood pressure regulation, and blood coagulation, as well as clinical conditions like ARDS, sepsis and ischemia/reperfusion injury.

HES colloids have negative charges on the surface of their molecules which render them unattracted to the glycocalyx, which also has negative surface charges.17 As a result they are unable to contribute to the integrity of the endothelium surface layer in a manner like albumin, whose distribution of positive and negative surface charges is more favorable to maintaining the integrity of the endothelial surface layer.19

Neither author has conflicts of interest to declare.

Ehab Farag, MD, FRCA D. John Doyle, MD, PhD Department of General Anesthesiology Cleveland Clinic Cleveland, OH


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