ONCOTIC, HEMODILUTIONAL, AND HEMOSTATIC EFFECTS OF ISOTONIC SALINE AND HYDROXYETHYL STARCH SOLUTIONS IN CLINICALLY NORMAL PONIES

Objective-To evaluate the oncotic, hemodilutional, and hemostatic effe cts of IV infusions of a large volume of isotonic saline solution and 2 doses of 6% hydroxyethyl starch (HES) in clinically normal ponies. A nimals-12 adult ponies. Procedure-Ponies were assigned to 3 treatment groups and received the following IV infusions: 80 ml of 0.9% sodium c hloride/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 for determination of colloid oncotic pressure (COP), PCV, plasma total pro tein concentration, platelet count, von Willebrand factor antigen (vWf :Ag) activity, fibrinogen concentration, prothrombin time, activated p artial thromboplastin time (APTT), and factor VIII coagulant (FVIII:C) activity. A rocket immunoelectrophoretic procedure was used for deter mination of vWf:Ag activity. A modification of the APTT assay was used for determination of FVIII:C activity. Cutaneous bleeding time was de termined, using a template method.Results-Mean COP was persistently in creased over baseline values in the face of hemodilution in HES-treate d ponies. Prothrombin time, APTT, and fibrinogen concentrations decrea sed after infusions and vWf:Ag and FVIII:C activities were decreased i n dose-dependent manner in HES-treated ponies. Though cutaneous bleedi ng time was not significantly affected in ponies of any group, a trend toward prolongation of bleeding time was evident in ponies receiving 20 ml of HES/kg. This trend appeared to be associated with marked decr ement in vWf:Ag activity at this dosage. Conclusions and Clinical Rele vance-Infusion of HES in clinically normal ponies increases COP, and e xerts dose-dependent hemodilutional effects and dose-dependent effects on specific hemostatic variables. Thus, HES may be useful for resusci tative fluid treatment of horses.