Aminocaproic acid's effectiveness as a hemostatic agent after gonadectomy

Why they did it

Retired racing greyhounds are popular pets, and because most are sexually intact at retirement, many veterinary practitioners perform ovariohysterectomy or orchiectomy around the time of their adoption. Previous studies have found that may have a higher than normal risk of postoperative bleeding 36 to 48 hours after routine gonadectomy. This is thought to be due to a defect in the clot maintenance (fibrinolytic) phase of coagulation, rather than due to causes of failure of primary hemostasis (e.g. thrombocytopenia, platelet dysfunction, von Willebrand's disease) or secondary hemostasis (e.g. hypofibrinogenemia, hypoprothrombinemia, hemophilia A or B, factor VII deficiency, combined clotting factor deficiencies). Given its documented effects as an inhibitor of fibrinolysis, epsilon aminocaproic acid (EACA) was evaluated in this study as a hemostatic agent in retired racing greyhounds undergoing ovariohysterectomy or orchiectomy.

What they did  

As part of a double-blinded, placebo-controlled study, 100 retired racing greyhounds were randomized to receive either EACA (500 mg orally every eight hours starting the night of surgery) or placebo for three days after routine gonadectomy. Hemostasis was assessed by using thromboelastography (TEG) and fibrinolysis variables (e.g. activated partial thromboplastin time, one-stage prothrombin time, D-dimer, antiplasmin, plasminogen). Samples were collected preoperatively and again 24, 48, and 72 hours after surgery. Bleeding was scored daily on a scale from 0 to 4, and photos of the surgical area were taken daily. Dogs were classified as bleeders if they had a score of ≥ 2.

What they found

Researchers found that 30% of dogs in the placebo group had delayed postoperative bleeding compared with 10% of those in the EACA group (P = 0.012). Bleeding was limited to cutaneous bruising at the surgical site. TEG measurements showed that dogs receiving EACA formed clots faster than those in the placebo group and that clot stability was greater. Coagulation assays were similar between the two groups, and no adverse effects were noted among the dogs receiving EACA.

The authors note that there was a trend toward enhancement of a hypercoagulable state in dogs treated with EACA based on TEG variables; however, further studies of this phenomenon are warranted. They also noted that while a 500 mg/dog dose of EACA was used in this study, a 15 mg/kg dose may be more appropriate because of a 19% increase in the odds of bleeding for every 1 kg increase in body weight.

Take-home message

Administration of EACA may safely decrease the risk of delayed postoperative bleeding in retired racing greyhounds undergoing spay or neuter surgery.

Marin LM, Iazbik MC, Zaldivar-Lopez S, et al. Epsilon aminocaproic acid for the prevention of delayed postoperative bleeding in retired racing greyhounds undergoing gonadectomy. Vet Surg 2012;41:594-603.

Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/22712787