Decreased Circulating Red Cell Mass Induced by Intravenous Acepromazine Administration Alters Viscoelastic and Traditional Plasma Coagulation Testing Results in Healthy Horses.
Authors: Mersich Ina, Bishop Rebecca C, Diaz Yucupicio Sandra, Nobrega Ana D, Austin Scott M, Barger Anne M, Fick Meghan E, Wilkins Pamela Anne
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Recognising coagulation abnormalities early in critically ill horses is vital for prognostic accuracy and treatment decisions, yet research into how anaemia itself—independent of underlying disease—affects standard coagulation testing remains limited in equine practice. Researchers administered acepromazine intravenously to eight healthy horses and measured changes in packed cell volume, viscoelastic testing (via VCM Vet), traditional plasma coagulation parameters, and splenic volume over a 12-hour period; the acepromazine caused a 13-percentage-point drop in PCV within one hour by triggering splenic contraction. Most notably, maximal clot formation (MCF) increased significantly despite the acute reduction in red cell mass, suggesting that purely anaemic states can produce falsely hypercoagulable results on viscoelastic analysis—a finding that mirrors observations in canine medicine but was previously undocumented in horses. Partial thromboplastin time showed transient shortening at one hour, though other traditional coagulation markers remained unchanged. For practitioners managing acutely anaemic horses or interpreting coagulation data from septic or haemorrhaging patients, these findings highlight an important confounding variable: viscoelastic hypercoagulability does not necessarily indicate pathological thrombotic risk when anaemia is the primary driver, and results must always be contextualised alongside clinical presentation and full haematological workup to avoid misdiagnosis and inappropriate anticoagulant therapy.
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Practical Takeaways
- •Acepromazine administration can significantly alter coagulation test results in horses through acute anemia rather than true coagulopathy; clinicians should consider timing of coagulation testing relative to sedative administration when evaluating critically ill horses
- •Viscoelastic testing appears more sensitive than traditional coagulation tests (PT/PTT) for detecting changes associated with decreased red cell mass in horses, similar to findings in dogs
- •When interpreting abnormal coagulation results in sedated equine patients, consider measuring PCV and splenic ultrasound to differentiate dilutional/hemodilution effects from primary hemostatic disorders
Key Findings
- •Acepromazine (0.1 mg/kg IV) induced a 13% point decrease in PCV within 1 hour, remaining decreased at 12 hours post-administration
- •Maximal clot formation (MCF) increased significantly following acepromazine-induced anemia, indicating viscoelastic hypercoagulability
- •Partial thromboplastin time (PTT) decreased at 1 hour post-acepromazine then increased at 12 hours, while other plasma coagulation parameters remained unchanged
- •Splenic volume increased following acepromazine administration at 1 hour, correlating with the induced decrease in circulating red cell mass