The Prevalence of Plasma Transfusion Reactions and the Preservation of Clotting Factors, Anti-Thrombin and Protein C in Equine Plasma
The hypothesis of this study was that acceptable levels of clotting factors, anti-thrombin (AT), and Protein C would be preserved in equine plasma following collection and storage and that the prevalence of plasma transfusion reactions would low and similar to other species.
The method of plasma harvest is as follows. Ten horses were anesthetized and blood was collected into sterile 5-liter fluid bags containing 250 ml of sodium citrate 4%. Once 25 liters of blood were harvested the horse was humanely euthanized. The blood was stored at 20°F for 48 hours in an upright position to allow separation of red blood cells via gravity sedimentation. The plasma was decanted into sterile 3-liter bags and stored at -20°F.
Three plasma samples were collected from each horse; S0 was collected prior to exsanguination and stored at-70°F for 72 hours, S1 was collected when the plasma was decanted and stored at-70°F for 24 hours. Both sample were shipped to the Comparative Coagulation Section of the Diagnostic Laboratory at Cornell University. The S90 sample was collected at plasma decant and stored for 90 days at -20°F and then shipped to the Comparative Coagulation Section of the Diagnostic Laboratory at Cornell University. Each plasma sample was analyzed for coagulation factors VII though XII, Protein C and AT. Coagulation factors were measured using factor deficient substrate and modified APTT assay. Anti-thrombin and Protein C activity were analyzed using chromogenic substrate assay method. No equine reference values exist for Protein C such that the assay was performed using a human standard. Data were analyzed using a One-way ANOVA with repeated measures, p < 0.05. Prevalence of plasma reactions was estimated by evaluating medical records from 46 consecutive horses that received plasma transfusions. The activity of factors IX, X, AT, and protein C significantly decreased from time S0 to time S1. The activity of factor XI significantly decreased from S1 to S90. However, the stability of factors VII, VIII, IX, XI, XII, Protein C and AT was maintained within the reference range following processing and 90 days of storage at-20°F. Only the activity of factor X significantly decreased below the reference value. The prevalence of plasma transfusion reactions was 11% (5/46 horses). Reactions included hives (n=1), tachycardia and pyrexia (n=2), tachypnea (n=1), and severe pruritus and swollen eyes (n=1). None of the reactions were fatal and all occurred during plasma administration.
Clotting factors, AT, and protein C were well preserved following harvest and storage of plasma. Prevalence of reactions to fresh frozen plasma was low and similar to other species, with tachycardia and pyrexia being the most common clinical signs.