Low dose calcium heparin in horses: plasma heparin concentrations, effects on red blood cell mass and on coagulation variables.

This research article assesses the effects of low dose calcium heparin on horses, specifically on plasma heparin concentrations, red blood cell count, and coagulation variables. Subcutaneous injections were administered to six healthy horses in specific intervals and hours, with various blood tests conducted to monitor the results, revealing significant increases in plasma heparin concentrations and large variations in individual responses.

Experiment Process and Parameters

• The experiment was performed on six healthy horses, which were given low dose calcium heparin injections subcutaneously (beneath the skin).
• An initial dose of 150 iu of heparin per kilogram body weight was given, followed by a maintenance dose of 120 iu/kg body weight.
• The injections were administered at regular intervals of 12 hours at specific timings (0900 and 2100 hrs), with blood samples for monitoring were collected variously.
• Plasma heparin concentrations were monitored for 84 hours during treatment and at different points during a control period.
• Additional variables, including Red Blood Cell (RBC) mass, plasma antithrombin III activity (AT III), activated partial thromboplastin time (APTT), and thrombin time (TT), were also monitored at different intervals throughout the experiment.

Observations and Findings

• Mean plasma heparin concentrations increased substantially after starting the injections until 32 hours after the last of seven injections.
• There were wide individual variances in sensitivity to heparin among the horses. Furthermore, there was an accumulation of heparin in the plasma over the course of prolonged administration.
• A distinct circadian rhythm was observed in the disposition of heparin, with peak values around 1300 hours and lowest values around 0500 hours. The peak-trough difference was about 50%.
• As the plasma heparin concentrations increased, there were erratic extensions of the average APTT and TT values, indicating variable effects on coagulation times.
• No significant impact on the curve of antithrombin III activity was observed from the administration of heparin.

Conclusions and Future Implications

• The study provides evidence that low dose calcium heparin administration results in significant increases in plasma heparin concentrations in horses.
• However, a large degree of individual variability indicates that dosages and treatment plans should be designed and modified based on individual responses to heparin.
• The observations regarding circadian rhythm in the management of heparin may have implications for optimizing timing of drug administration in order to achieve desired plasma concentrations.