The Effects of Intravenous Formaldehyde on Hemostasis in Normal Horses

1. Introduction

For many years, IV formaldehyde therapy has been advocated for use in horses for control of purpura hemorrhagica and other forms of hemorrhaging.¹ However, few scientific reports support its efficacy or safety. In 1940, Roberts¹ reported administration of 4 to 50 ml of 4% to 12% formalin solution in 400 to 500 ml distilled water to horses, with an average decrease in coagulation time of 75.2%. Higher doses were associated with adverse reactions including restlessness, lacrimation, salivation, nasal discharge, frequent defecation, sweating, muscle tremors and abdominal pain.¹ Administration of 5% formalin to goats at 1.1 ml/kg markedly decreased clotting time and bleeding time for approximately 30 minutes postinjection.² Decreases in bleeding time occur with enhanced primary hemostasis, usually indicative of a platelet or endothelial change. Formaldehyde is useful as a tissue fixative because it cross-links proteins. This cross-linking might alter platelet or endothelial cell surface proteins, resulting in activation of platelets or decreased endothelial permeability.³ For horses, doses of approximately 10 ml of 37% formaldehyde or 30 to 150 ml of 10% buffered formalin in 1 l of isotonic fluids have recently been recommended for control of bleeding.4 In addition to the gross behavioral changes observed by Roberts in formaldehyde-treated horses,¹ formaldehyde is potentially hepatotoxic; high concentrations of formaldehyde dehydrogenase in the liver are responsible for catabolism of formaldehyde.5 We investigated the effects of IV formaldehyde administration on coagulation parameters and bleeding time in normal, healthy horses and horses with prolonged bleeding times secondary to aspirin administration to determine if formaldehyde is safe and efficacious for enhancement of hemostasis.

2. Materials and Methods

For all experiments, six horses were used in a blinded, two-way cross-over design. Before use, each horse was determined to be in good health by general physical examination, complete blood count (CBC) and serum biochemical profile. Horses were housed in individual box stalls with freely available grass hay and water. […]