Plasma heparin values and hemostasis in equids after subcutaneous administration of low-dose calcium heparin.

The study investigates the effects of different doses of a blood thinner, calcium heparin, when administered to equids (horse family) and how it impacts their blood’s clotting ability. Several measurements, including concentrations of heparin and antithrombin III in their blood, were recorded over time to understand the actions of heparin.

Study Design and Methodology

• Five different doses of calcium heparin were administered to five groups of equids (group of 5 each) subcutaneously (SC). The doses were 40, 60, 80, 100, and 125 U of heparin per kilogram of body weight while another group of 11 equids were given a dose of 150 U/kg.
• The values of plasma heparin and the activities of antithrombin III were measured using chromogenic substrate methods.
• The clotting times – activated partial thromboplastin and thrombin times – were evaluated using standard coagulation assays.
• These tests were conducted every hour or every 2 hours for antithrombin III, over a period of 12 hours following the heparin administration.

Findings

• The smallest dose of heparin (40 U/kg) did not show considerable impact on plasma heparin values.
• After equids received a dose of 150 U of heparin per kg, the heparin concentration in their plasma increased significantly between the 2nd and 7th hour post-administration. This increase was sustained up until the 11th hour.
• The presence of antithrombin III and clotting times were not significantly impacted by the administered doses of heparin.

Cumulative Studies

• Two equids were subjected to multiple injections of 150 U of heparin per kg at 12-hour intervals. After the third injection, their mean plasma concentration of heparin reached 0.20 U/ml and after the seventh injection, the mean concentration was 0.22 U/ml.
• Four other equids were administered an initial dose of 150 U/kg of heparin followed by six doses of 125 U/kg of heparin, also at 12-hour intervals. The mean plasma heparin concentration reached a maximum of 0.12 U/ml after the third injection and 0.18 U/ml after the seventh injection.
• After the repeat injections, moderate swelling was observed at the injection sites in these equids.