Cardiovascular, colloid osmotic pressure, and hemostatic effects of 2 formulations of hydroxyethyl starch in healthy horses.
Authors: Epstein K L, Bergren A, Giguère S, Brainard B M
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: HES Formulations in Equine Fluid Therapy Hydroxyethyl starch solutions are widely used for volume expansion in equine emergency and perioperative medicine, yet concerns persist about their effects on coagulation. Epstein and colleagues conducted a randomised crossover study in eight healthy horses to directly compare a high molecular weight hetastarch (600/0.75) against a lower molecular weight tetrastarch (130/0.4) formulation and saline control, measuring cardiovascular function, colloid osmotic pressure (COP), and platelet function over 24 hours. Both HES formulations significantly improved systolic and mean arterial pressures compared to saline and maintained elevated COP longer—tetrastarch sustaining this effect for 8 hours versus hetastarch's 1 hour—but hetastarch caused substantially prolonged platelet dysfunction, with clotting times remaining elevated at 174–178 seconds at 8–24 hours compared to 101–121 seconds for tetrastarch. For practitioners administering fluid boluses in compromised horses, tetrastarch emerges as the superior option: it provides equivalent haemodynamic benefits and superior COP maintenance whilst incurring a significantly lower coagulation penalty, making it the more prudent choice where concerns about bleeding risk already exist.
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Practical Takeaways
- •Tetrastarch offers superior hemostatic profile with shorter duration of coagulation abnormalities—consider for horses requiring colloid support where bleeding risk is a concern
- •If using hetastarch, monitor for prolonged clotting times extending 24 hours post-administration and avoid use in horses with pre-existing hemostatic compromise
- •Both HES formulations effectively support blood pressure and colloid osmotic pressure better than saline alone, justifying their use in fluid resuscitation protocols in healthy horses
Key Findings
- •Both hetastarch (600/0.75) and tetrastarch (130/0.4) increased systolic and mean arterial pressure compared to saline, with increases of 5-8 mmHg systolic pressure
- •Tetrastarch produced more sustained colloid osmotic pressure effect (25.9 mmHg at 8 hours) compared to hetastarch (24.0 mmHg at 1 hour), both superior to saline (22.9 mmHg at 8 hours)
- •Hetastarch caused significantly greater prolongation of clotting time at 8 and 24 hours (178.6 and 174.2 seconds) compared to tetrastarch (121.9 and 100.8 seconds) and saline (108.3 and 118.7 seconds)
- •Both HES solutions produced transient decreases in packed cell volume at 1.5 hours (approximately 6% reduction) through hemodilution