Retrospective evaluation of shortened prothrombin time or activated partial thromboplastin time for the diagnosis of hypercoagulability in dogs: 25 cases (2006-2011)

INVESTIGATION OF A POINT-OF-CARE VISCOELASTIC COAGULATION MONITOR AND ITS COMPARISON TO THROMBOELASTOGRAPHY IN CLINICALLY HEALTHY AFRICAN ELEPHANTS (LOXODONTA AFRICANA)

Elephant endotheliotropic herpesvirus (EEHV) can induce fatal hemorrhagic disease (HD) in African elephants (Loxodonta africana). Once clinical signs develop, progression is rapid, even with aggressive treatment. There is a critical need to develop point-of-care diagnostic tests to aid in identification of EEHV-HD prior to the onset of overt clinical signs. Study objectives were to investigate a novel, point-of-care viscoelastic coagulation monitor (VCM Vet), compare the results to thromboelastography (TEG), and report traditional hemostatic analytes in adult African elephants. Whole blood was collected from seven clinically healthy elephants (four females and three males, 18-47 yr) and analyzed in duplicate via VCM Vet and kaolin-activated TEG 1-3 and 30 min following collection, respectively. Separated plasma was frozen for ancillary coagulation testing. Both analyses generated quantifiable clotting reactions with variables (median [range]) describing clot formation rate (VCM Vet, clot time = 682 s [530-987 s], clot formation time = 244 s [186-744 s], Alpha = 40° [14-47°]; TEG, reaction time = 6.2 min [3.7-11.8 min], kinetic time = 1.3 min [0.9-2.6 min], Alpha = 70° [57-77°]), clot strength (VCM Vet, maximum clot formation = 34 units [20-45 units]; TEG, maximum amplitude = 75 mm [69-80 mm], shear elastic modulus strength = 14.7 Kdynes/s [11.3-19.5 Kdynes/s]), and clot lysis (VCM Vet, lysis index at 30 min = 100% [100-99%], lysis index at 45 min = 98% [95-100%]; TEG, lysis index at 30 min = 0% [0-0.4%], lysis index at 60 min = 1.4% [0-2.6%]) recorded. Additional testing (median [range]) included D-dimer concentration (33 ng/ml [28-94 ng/ml]), prothrombin time (12.4 s [12.2-13.2 s]), activated partial thromboplastin time (17.2 s [14.2-18.8 s]), and fibrinogen concentration (297 [282-383] mg/dL). Tracings generated by VCM Vet and TEG were clinically similar, and there was visual agreement and minimal difference between quantitative variables for duplicate tests. VCM Vet is a promising, user-friendly tool for use in identification and management of coagulopathies in African elephants.

Reference interval for the C-ACT activated clotting time test in healthy dogs using a water bath and manual assessment of clot formation

AIMS

To establish a reference range for the canine C-ACT activated clotting time (ACT) test using a water bath and visual clot assessment technique.

METHODS

Healthy, privately owned dogs (n = 48) were prospectively recruited to the study. Blood samples were collected via direct jugular venipuncture for complete blood count, serum biochemistry, prothrombin time (PT) and activated partial thromboplastin time (aPTT). Five animals with major abnormalities or who became agitated during phlebotomy were excluded. For the 43 remaining animals, 2 mL of blood was then collected via the cephalic vein and added directly to a C-ACT tube that was shaken vigorously before being placed in a water bath at 37°C. Tubes were visually assessed for clot formation and C-ACT was recorded in seconds when the magnet within the tube lodged in the clot.

RESULTS

Forty-three animals were eligible for inclusion. The nonparametric reference interval (capturing the central 95% of the data) was 50-80 seconds, with a 90% CI for the lower limit of 50-55 seconds and a 90% CI for the upper limit of 75-80 seconds. The C-ACT ACT test had a positive correlation with aPTT (0.42, 95% CI = 0.13-0.64). There was no evidence of a correlation between C-ACT ACT and age, weight, PT, haematocrit, white blood cell count, platelet count or total protein.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of this study suggest that the normal reference interval for ACT in dogs using C-ACT tubes in a 37°C water bath is 50-80 seconds. Care should be taken extrapolating the results of this study to the general population, as the smaller study design had less control for confounders than a larger study. However, when using the described analytical methods, C-ACT tube ACT test results > 80 seconds should be considered prolonged in dogs and should prompt further investigation.

ABBREVIATIONS

ACT: Activated clotting time; aPTT: Activated partial thromboplastin time; EDTA: Ethylenediaminetetraacetic acid; Hct: Haematocrit; PT: Prothrombin time.

Risk factors for hypercoagulability after laparoscopic hepatic haemangioma resection

Background

Laparoscopic hepatectomy with a small incision, light abdominal wall trauma and rapid postoperative recovery has been widely used in the surgical treatment of benign liver diseases. However, the occurrence of complications, such as deep-vein thrombosis, associated with laparoscopic techniques has raised concerns. This study aimed to investigate the factors influencing the development of a hypercoagulable state in patients following laparoscopic hepatic haemangioma resection.

Materials and Methods

Between 2017 and 2019, 78 patients to be treated by laparoscopic hepatic haemangioma resection were selected prospectively for the study. The differences in relevant clinical factors between patients with and without blood hypercoagulability at 24 h after surgery were compared, and the factors influencing the development of blood hypercoagulability after surgery were analysed.

Results

The study included 78 patients, split into the hypercoagulable group (n = 27) and nonhypercoagulable group (n = 51). Compared with patients who did not develop blood hypercoagulability, patients who did had significantly higher preoperative levels of fibrinogen (Fib), D-dimer (D-Di), fibrinogen degradation products (FDP), platelet count (PLT), low-density lipoprotein cholesterol (LDL-C) and history of hyperlipidaemia whereas high-density lipoprotein cholesterol (HDL-C) levels were significantly lower (P < 0.05.) in hypercoagulable group. Univariate and multifactorial logistic regression analyses showed that a history of hyperlipidaemia, Fib ≥3.83 g/L, D-Di ≥9.12 μg/ml, FDP ≥14.64 μg/ml, PLT ≥292 × 109/L, HDL-C ≥1.25 mmol/L and LDL-C ≥2.03 mmol/L was the most common independent risk factors for the development of a hypercoagulable state of blood in patients after laparoscopic hepatic haemangioma resection (P < 0.05).

Conclusion

For patients undergoing laparoscopic hepatic haemangioma resection, attention should be paid to the development of a hypercoagulable state in those with the risk factors described in this study.

Dímero-D en perros con cáncer relacionado al grado, tipo de tumor y conteo plaquetario

En la actualidad se han detectado varios trastornos clínicos relacionados con alteraciones hemostáticas en pacientes con Cáncer, reportados en humanos y perros. Ante esta realidad se proponen nuevos estudios diagnósticos como el Dímero-D (DD) aplicable a pacientes oncológicos. En Medicina Veterinaria, esta prueba es relativamente nueva y sirve para descartar posibles episodios trombóticos y ayuda al diagnóstico precoz de enfermedades relacionadas con la trombosis. El presente trabajo de investigación tuvo como objetivo medir valores de DD en nanogramos·mililitros-1 (ng·mL-1) en perros con cáncer, en los cuales se hizo un análisis multicéntrico de un total de 40 pacientes (n=40) en dos Hospitales Veterinarios de Quito y Guayaquil, en Ecuador. A los pacientes diagnosticados como oncológicos se les realizó una historia clínica detallada, posteriormente se les tomó una muestra de sangre en un tubo citratado, para después ser enviada al laboratorio donde se aplicaría la técnica de inmunofluorescencia para medir la cantidad de DD a través del equipo V-Check, V200 de Bionote, China, y una muestra en tubo con EDTA para hemograma en un equipo automatizado. Se analizaron además los resultados de las histopatologías, clasificándolos según su tipo y grado de tumor y se correlacionaron con los resultados del DD y conteo plaquetario. Entre los resultados se encontró correlación de DD con el tipo y grado de tumor, como también DD y el conteo de plaquetas; en este estudio, los tumores como hemangiosarcomas de bazo, los carcinomas y adenocarcinomas fueron los más comunes en presentar elevaciones de DD, y al igual que aquellos que presentaron una calificación más alta en la escala de grados histológicos.

2022 Update of the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) Domain 1- Defining populations at risk

OBJECTIVES

To expand the number of conditions and interventions explored for their associations with thrombosis in the veterinary literature and to provide the basis for prescribing recommendations.

DESIGN

A population exposure comparison outcome format was used to represent patient, exposure, comparison, and outcome. Population Exposure Comparison Outcome questions were distributed to worksheet authors who performed comprehensive searches, summarized the evidence, and created guideline recommendations that were reviewed by domain chairs. The revised guidelines then underwent the Delphi survey process to reach consensus on the final guidelines. Diseases evaluated in this iteration included heartworm disease (dogs and cats), immune-mediated hemolytic anemia (cats), protein-losing nephropathy (cats), protein-losing enteropathy (dogs and cats), sepsis (cats), hyperadrenocorticism (cats), liver disease (dogs), congenital portosystemic shunts (dogs and cats) and the following interventions: IV catheters (dogs and cats), arterial catheters (dogs and cats), vascular access ports (dogs and cats), extracorporeal circuits (dogs and cats) and transvenous pacemakers (dogs and cats).

RESULTS

Of the diseases evaluated in this iteration, a high risk for thrombosis was defined as heartworm disease or protein-losing enteropathy. Low risk for thrombosis was defined as dogs with liver disease, cats with immune-mediated hemolytic anemia, protein-losing nephropathy, sepsis, or hyperadrenocorticism.

CONCLUSIONS

Associations with thrombosis are outlined for various conditions and interventions and provide the basis for management recommendations. Numerous knowledge gaps were identified that represent opportunities for future studies.

Pre-operative Hemostatic Status in Dogs Undergoing Splenectomy for Splenic Masses

Portal system thrombosis is a rare but potentially fatal complication of splenectomy in dogs. The mechanism behind development of post-operative portal system thrombosis is unclear but may include alterations of portal blood flow following surgery, acquired hypercoagulability and endothelial dysfunction. The aim of the study was to evaluate hemostatic biomarkers in hemodynamically stable (heart rate <130 beats/min, blood lactate < 2.5 mMol/L) and non-anemic (hematocrit >35%) dogs prior to splenectomy for splenic masses. Our hypothesis was that this population of stable dogs would have pre-existing laboratory evidence of hypercoagulability unrelated to shock, bleeding, anemia, or other pre-operative comorbidities. Pre-operatively, abdominal ultrasonography was performed and blood was collected for platelet enumeration, prothrombin time (PT), activated partial thromboplastin time (aPTT), kaolin-activated thromboelastography (TEG), fibrinogen, von Willebrand factor activity (vWF:Ag), antithrombin and thrombin-antithrombin complex (TAT). Histopathological diagnosis and 30-day survival were recorded. None of the 15 enrolled dogs had pre-operative sonographic evidence of portal system thrombosis. Three of fifteen dogs were thrombocytopenic, three had thrombocytosis, three were hyperfibrinogenemic, one had low vWF:Ag, three had mild prolongations of PT and none had abnormal aPTT. Based on the TEG G value, 13/15 dogs were hypercoagulable (mean ± SD 13.5 ± 5.4 kd/s). Antithrombin deficiency was identified in 9/15 dogs (mean ± SD 68.7 ± 22.7%) with 5/9 having concurrently elevated TAT suggesting active thrombin generation. No dogs developed portal system thrombosis and all achieved 30-day survival. Pre-operative hypercoagulability was recognized commonly but its association with post-operative thrombosis remains undetermined.

Procoagulant and anticoagulant plasma indicators in diabetic dogs showing increased antithrombin III levels in canine diabetes mellitus

Background

Diabetes mellitus (DM) often leads to dangerous thromboembolic complications in humans. DM is also a relatively common endocrinopathy of dogs. There is scarce information regarding procoagulant and anticoagulant plasma indicators in this disease. The aim of the study was to evaluate the levels of the selected plasma haemostatic parameters in dogs suffering from diabetes. The study group consisted of 20 dogs meeting all the inclusion criteria, with fasting glycaemia exceeding 11.1 mmol/l. The control group consisted of 15 healthy dogs presented for routine examination. An evaluation of the prothrombin time (PT); and fibrinogen, D-dimer and antithrombin III (ATIII) levels was performed.

Results

Except for ATIII activity, the haemostatic parameter differences were not statistically significant. High values of ATIII activity were observed in 90% of diabetic dogs. On average, the values amounted to 166.6% and were 31.4% higher than those in the control group. The ATIII activity in the diabetic group was significantly higher than that in the control group (p = 0.0004).

Conclusions

Here, we report elevated levels of ATIII in diabetic dogs. This finding may suggest the protective role of ATIII against potential thrombotic events. However, the exact role of ATIII in dog diabetes remains unclear.

Hemostatic Analysis of Simulated Gloydius ussuriensis Envenomation Using Canine Blood: A Comparison of Thromboelastography and Classical Coagulation Tests

Snake envenomation may lead to venom-induced consumptive coagulopathy (VICC), usually diagnosed by classical coagulation tests (CCTs), such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). However, the results of CCTs are frequently normal in the initial stages, which may delay anti-venom treatments. Thromboelastography (TEG) is a point-of-care and real-time diagnostic tool that enables a comprehensive assessment of the coagulation process. This in vitro study aimed to determine concentration-dependent changes in canine blood caused by Gloydius ussuriensis (G. ussuriensis) envenomation using TEG and CCTs. Lyophilized G. ussuriensis venom was reconstructed using mouse intravenous lethal dose 50 (LD50iv) and serially diluted to 25% LD50iv, 50% LD50iv, and 75% LD50iv to reproduce VICC at different concentrations. Normal saline was used for the control. We compared TEG values of the reaction time (R), kinetic time (K), rate of clot formation (α-angle), maximum amplitude (MA), fibrinolysis at 30 min (LY30), and global strength of the clot (G) with those of PT, aPTT, fibrinogen, and platelet counts (PLTs). Most TEG parameters, except R and LY30, demonstrated statistically significant changes compared with the control at all concentrations. CCTs, except PLTs, revealed significant changes at ≥50% LD50iv. Thus, TEG could be a useful diagnostic strategy for early VICC and preventing treatment delay.

Evaluation of serum histone concentrations and their associations with hemostasis, markers of inflammation, and outcome in dogs with naturally occurring acute pancreatitis

OBJECTIVE

To compare serum concentrations of histones and inflammatory markers in dogs with acute pancreatitis and healthy control dogs, investigate associations of these variables with coagulation test results and survival (vs nonsurvival) to hospital discharge, and examine the prognostic utility of clinical findings and routine laboratory and coagulation tests in affected dogs.

ANIMALS

36 dogs.

PROCEDURES

Dogs with findings consistent with acute pancreatitis (n = 29) and healthy control dogs (7) were enrolled in a prospective, observational study. Serum concentrations of histones, interleukin (IL)-6, and tumor-necrosis factor-α were assessed for all dogs. Clinical (including ultrasonographic) findings, relevant history, routine laboratory and coagulation test results, and outcomes were recorded for dogs with pancreatitis. Variables were assessed to determine an association with outcome for affected dogs and hospitalization time for survivors; histone concentrations and markers of inflammation were compared among survivors, nonsurvivors, and controls. Correlation between quantitative variables was investigated.

RESULTS

Serum histone and IL-6 concentrations did not differentiate survivors (n = 23) from nonsurvivors (6); IL-6 concentrations in affected dogs were correlated with 1,2-o-dilauryl-rac-glycero glutaric acid-(6'-methylresorufin) ester lipase activity (r_S = 0.436) and hospitalization time (r_S = 0.528). Pancreatitis-associated peritoneal fluid, obtundation, and jaundice were more common, and serum bilirubin concentration, serum alanine aminotransferase and aspartate aminotransferase activities, and prothrombin and activated partial thromboplastin times were greater in nonsurvivors than in survivors. Thromboelastometric changes consistent with hypercoagulability were detected in survivors; hypocoagulability was detected in 2 nonsurvivors.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum histone concentrations were not associated with presence of acute pancreatitis or outcome for affected dogs. Further research is needed to investigate the clinical and therapeutic implications of hypocoagulability, hepatocellular injury, and pancreatitis-associated peritoneal fluid in affected dogs.

Coagulation, Vascular Morphology, and Vasculogenesis in Spinal Ligament Ossification Model Mice

STUDY DESIGN

In vivo studies of the vascular system in ossification of the posterior longitudinal ligament (OPLL) model mice.

OBJECTIVE

The aim of this study was to investigate blood coagulability, vascular morphology, and vasculogenesis capability, known as venous thromboembolism (VTE) risk factors in the ossification model, tiptoe walking (ttw) mice.

SUMMARY OF BACKGROUND DATA

Patients with OPLL are more likely to develop VTE after spinal cord injury. Capillary mesh invasion of spinal ligaments precedes spinal ligament ossification in ttw mice. Investigation on vascular systems of ttw mice may contribute to clarifying its pathology.

METHODS

Coagulability of blood samples from ttw and C57BL/6 (WT) mice were evaluated at 8, 16, and 24 weeks of age. Vascular morphology was assessed from a Hematoxylin-Eosin stained section by measuring vessel area. A tube formation assay was performed with endothelial cells isolated from the aorta to assess vasculogenesis.

RESULTS

Prothrombin time was significantly shorter in ttw mice than in WT at 8 and 16 weeks. Fibrinogen had a greater increase in ttw mice than in WT at 16 weeks. The vascular area and vascular wall area were significantly smaller in ttw mice than in WT at all timepoints. The ratio of vascular wall area to vascular area was significantly smaller in ttw mice than in WT at 24 weeks. The endothelial cells from ttw mice formed significantly higher numbers of total branching points than WT cells.

CONCLUSION

Ossification model mice had impaired blood coagulation and vascular morphology and high capacity for vasculogenesis. With regard to the pathogenesis of VTE, ttw mice harbor an environment that promotes the development of VTE.Level of Evidence: N/A.

Chinese expert consensus on diagnosis and treatment of trauma-induced hypercoagulopathy

Trauma-induced coagulopathy (TIC) is caused by post-traumatic tissue injury and manifests as hypercoagulability that leads to thromboembolism or hypocoagulability that leads to uncontrollable massive hemorrhage. Previous studies on TIC have mainly focused on hemorrhagic coagulopathy caused by the hypocoagulable phenotype of TIC, while recent studies have found that trauma-induced hypercoagulopathy can occur in as many as 22.2-85.1% of trauma patients, in whom it can increase the risk of thrombotic events and mortality by 2- to 4-fold. Therefore, the Chinese People's Liberation Army Professional Committee of Critical Care Medicine and the Chinese Society of Thrombosis, Hemostasis and Critical Care, Chinese Medicine Education Association jointly formulated this Chinese Expert Consensus comprising 15 recommendations for the definition, pathophysiological mechanism, assessment, prevention, and treatment of trauma-induced hypercoagulopathy.

The Use of Antithrombotics in Critical Illness

Hypercoagulable tendencies may develop in critically ill dogs and to a less known extent, cats. Although the use of antithrombotics is well-established in critically ill people, the indications and approach are far less well-known in dogs and cats. The goal of this article was to review the relevant CURATIVE guidelines, as well as other sources, and to provide recommendations for critically ill patients with directions for future investigation.

Abnormal platelet activity in dogs and cats - impact and measurement

Abnormal platelet activity can either lead to bleeding tendencies or inappropriate thrombus formation and can occur secondarily to a wide variety of disease processes, with a range of clinical consequences and severity. This article will discuss the pathophysiology of platelet function abnormalities and consider a logical diagnostic approach applicable to veterinary practice. Recent advances in platelet function testing will then be discussed, with regards to detection of platelet dysfunction and tailoring of pharmacological manipulation. Although many of these tests are still confined to research or academic institutions, techniques for indirectly assessing platelet function are starting to become more widely available. Although we still require further research to develop guidelines for the use of these tests in clinical decision-making, the recent advances in this field are an exciting step forward in being able to detect and manage platelet dysfunction in both primary care and referral practice.

Efficacy of specific antivenom and fresh frozen plasma in reversing Daboia palaestinae venom-induced hemostatic derangement

OBJECTIVES

To evaluate the in vitro efficacy of specific Daboia (Vipera) palaestinae (Dp) antivenom or fresh frozen plasma (FFP) against Dp venom-induced hemostatic changes DESIGN: In vitro study.

SETTING

Laboratory of a university referral hospital.

ANIMALS

Five healthy dogs.

INTERVENTIONS

Rotational thromboelastometry (including recombinant tissue factor or kaolin activators [EXTEM and INTEM, respectively]) and conventional hemostatic tests were evaluated in citrated whole blood samples that underwent 4 treatments: (1) no additives (control); (2) 15 μg of Dp venom; (3) 15 μg of Dp venom and 10 μL of specific Dp antivenom; (4) 15 μg of Dp venom and 0.3 mL of FFP. A linear mixed-effects regression model was used to compare results between each treatment and the control.

MEASUREMENTS AND MAIN RESULTS

Dp-venom engendered statistically significant (P < 0.05) EXTEM changes in 8/17 variables, all indicative of hypercoagulability, which were negated by antivenom but not with FFP. Similarly, Dp-venom induced hypercoagulable, hyperfibrinolytic changes in 12 of 17 INTEM variables, of which only 5 of 12 were negated by antivenom but not with FFP. Fibrinogen concentration was decreased, and the activated partial thromboplastin time (aPTT) was shortened (P < 0.05 for both) in all treatments compared to the control.

CONCLUSIONS

This study demonstrated the ephemeral procoagulant phase of Dp envenomation for the first time. Many venom-induced thromboelastometric changes were reversed by specific antivenom but not with FFP. Prospective clinical studies are warranted to investigate whether the present findings translate to clinical efficacy.

Outcome in dogs undergoing adrenalectomy for small adrenal gland tumours without vascular invasion

Veterinary studies have reported the outcome of adrenalectomies in dogs; however, these studies typically include a wide variety of adrenal tumour sizes, including cases with or without vascular invasion. The purpose of this study was to report outcome in a cohort of dogs with histologically confirmed small adrenal tumours without vascular invasion treated with adrenalectomy. This retrospective study was conducted using data from the University of Florida and University of California-Davis databases between 2010 and 2017. Dogs were included if they underwent excision of an adrenal gland tumour with a maximal diameter ≤ 3 cm, without evidence of vascular invasion to any location as assessed via computed tomography. Fifty-one dogs met the inclusion criteria. The short-term survival rate of dogs undergoing adrenalectomy was 92.2%, and one-year disease-specific survival was 83.3%. Twenty-eight of 51 (54.9%) dogs were diagnosed with a malignancy. Minor complications were observed commonly intra-operatively and post-operatively. Major complications were observed in six dogs, and included sudden death, respiratory arrest, acute kidney injury, haemorrhage, hypotension and aspiration pneumonia. Short-term mortality occurred in four dogs. Sudden death and haemorrhage were the most common major complications leading to death. While adrenalectomy is sometimes controversial because of the high perioperative mortality rates previously reported, the results of this study support that adrenalectomy for small tumours with no vascular invasion can be performed with low risk.

Multicenter investigation of hemostatic dysfunction in 15 dogs with acute pancreatitis

OBJECTIVE

To characterize hemostatic profiles in dogs with acute pancreatitis.

DESIGN

Prospective and observational study.

SETTING

Tertiary referral centers.

ANIMALS

Fifteen client-owned dogs with acute pancreatitis enrolled between December 1, 2011 and June 1, 2012.

MATERIALS AND METHODS

Blood samples were collected on admission for measurement of platelet count, PCV, thromboelastography (TEG), antithrombin, prothrombin time, activated partial thromboplastin time, D-dimer, von Willebrand factor, and fibrinogen values, which were compared to reference intervals derived from healthy dogs. The Wilcoxon rank-sum test was used to test for differences in continuous variables between study subjects and reference intervals.

MEASUREMENTS AND MAIN RESULTS

Dogs with acute pancreatitis were globally hypercoagulable using TEG when compared with reference intervals. Dogs with acute pancreatitis had significantly higher D-dimers (1,144 μg/L vs 251 μg/L [6264.5 vs 1374.5 nmol/L]; P = 0.001), fibrinogen (837 vs 232 mg/dL [8.37 vs 2.32 g/L]; P < 0.001), and von Willebrand factor (92.9% vs 65.1%; P = 0.02) as well as significantly lower antithrombin (85.7% vs 120%; P < 0.001) and prothrombin time values (3.8 vs 7.6 sec; P < 0.001) than reference intervals.

CONCLUSIONS

Laboratory evidence of hypercoagulability was present in dogs with acute pancreatitis. TEG may be useful in dogs with acute pancreatitis for monitoring response to therapy and guiding therapeutic interventions.

Effects of immunosuppressive agents on the hemostatic system in normal dogs

Background

In dogs, the effects of immunosuppressive medications on hemostasis are not well known.

Hypothesis/Objectives

The objective was to determine the effects of immunosuppressive medications on primary and secondary hemostasis. Our hypothesis was that cyclosporine and prednisone would increase markers of hypercoagulability and thromboxane synthesis, while azathioprine, mycophenolate mofetil, and leflunomide would have minimal effects on hemostasis.

Animals

Eight healthy dogs.

Methods

A randomized, cross‐over study used aggregometry, the PFA‐100 platelet function analyzer, viscoelastometry, platelet count, and prothrombin and activated partial thromboplastin times to evaluate hemostasis during the administration of prednisone, azathioprine, cyclosporine, mycophenolate mofetil, and leflunomide for 1 week each at standard oral doses. Urine 11‐dehydro‐thromboxane‐B₂ (11‐dTXB₂) and 6‐keto‐prostaglandin‐F_1α (6‐keto‐PGF_1α) concentrations, normalized to urine creatinine concentration, were measured.

Results

The aggregometry amplitude decreased from 51 ± 21 to 27 ± 14 (P = .002) during leflunomide treatment (ADP activation), but there were no differences in amplitude (P = .240) for any medications when platelets were activated with collagen. For all medications, there were no significant differences in viscoelastometry indices (ACT, P = .666; ClotRate, P = .340; and platelet function, P = .411) and platelet count (P = .552). Compared with pretreatment values, urinary 11‐dTXB₂‐to‐creatinine ratio increased (P = .001) after drug administration (from 3.7 ± 0.6 to 5.6 ± 1.1). Cyclosporine was associated with an increase (P < .001) in the 6‐keto‐PGF_1α‐to‐creatinine ratio (from 10.3 ± 4.6 to 22.1 ± 5.3).

Conclusions and Clinical Importance

Most immunosuppressive drugs do not enhance platelet function or coagulation in healthy dogs, suggesting that these medications might not predispose hypercoagulable dogs to thromboembolism. The results of our study need to be correlated with the clinical outcomes of hypercoagulable dogs.