Oncotic, hemodilutional, and hemostatic effects of isotonic saline and hydroxyethyl starch solutions in clinically normal ponies.

The study examines the effects of intravenous infusions of isotonic saline solution and two doses of 6% hydroxyethyl starch (HES) on several blood parameters in healthy ponies. The results reveal that the infusion of HES impacts colloid oncotic pressure (COP), demonstrates dose-dependent hemodilutional effects, and influences specific blood clotting variables, suggesting a potential role for HES as a resuscitative fluid treatment in horses.

Research Methodology

• The research involved 12 adult ponies. The animals were divided into three groups, each receiving different intravenous (IV) infusion treatments: 80 ml of 0.9% sodium chloride/kg, 10 ml of 6% HES in 0.9% sodium chloride/kg, or 20 ml of 6% HES in 0.9% sodium chloride/kg.
• Blood samples were collected from the ponies to determine a variety of factors, including colloid oncotic pressure (COP), packed cell volume (PCV), plasma total protein concentration, platelet count, von Willebrand factor (vWf:Ag) activity, fibrinogen concentration, prothrombin time, activated partial thromboplastin time (APTT), and factor VIII coagulant (FVIII:C) activity.
• Additional tests conducted included a rocket immunoelectrophoretic procedure to determine vWf:Ag activity and using a modified APTT assay to determine FVIII:C activity. Cutaneous bleeding time was also measured through a template method.

Research Outcomes

• The COP stayed elevated above the baseline values in horses treated with HES, despite an observed hemodilution. Hemodilution is the dilution of the blood due to an increase in the plasma volume, usually due to an infusion.
• The prothrombin time, APTT, and fibrinogen concentrations decreased after infusions.
• The vWf:Ag and FVIII:C activities decreased in HES-treated horses in a dose-dependent manner, meaning effects were seen proportional to the amount of HES administered.
• Although cutaneous bleeding time was not significantly influenced in any group of ponies, a noteworthy extension of bleeding time was apparent in the group that received 20 ml of HES/kg. This increase appeared to be associated with a marked reduction in vWf:Ag activity at this dosage.

Conclusions

• The researchers concluded that the infusion of HES in clinically healthy ponies increases COP. Furthermore, it has a dose-dependent effect on hemodilution and specific hemostatic (blood clotting) variables.
• These findings suggest that HES may serve as a useful resuscitative fluid treatment in horses, potentially aiding in the treatment of injuries or in surgical scenarios requiring blood dilution or volume expansion.