Using the laboratory to predict thrombosis in dogs: An achievable goal?

Evaluation of clopidogrel, hypercoagulability, and platelet count in dogs undergoing splenectomy for splenic masses

Dogs that had splenectomy are predisposed to fatal thrombotic conditions, and thrombocytosis is a risk factor for post-splenectomy hypercoagulability. However, in veterinary medicine, there are no specific therapeutic approaches for managing this hypercoagulability. This study aimed to determine the preventive effect of clopidogrel on post-operative hypercoagulability during the first 2 weeks post-splenectomy in dogs with splenic masses. This study included 12 dogs that had splenectomy. Seven dogs received no treatment (group A), and five were treated with clopidogrel (group B). Clopidogrel was loaded at 10 mg/kg on day 2 and continued at 2 mg/kg until day 14. Blood samples were collected on the day of surgery and 2, 7, and 14 days after splenectomy in both groups. In group B, thromboelastography (TEG) was performed on the same days. In group A, there was significant elevation of platelet counts on days 7 (p = 0.007) and 14 (p = 0.001) compared to day 0. In group B, the platelet counts were significantly elevated on day 7 (p = 0.032) but no significant difference was found on day 14 compared to day 0. Platelet counts on day 14 were significantly higher in group A than in group B (p = 0.03). The lower platelet counts were correlated with alterations in TEG parameters, and no significant differences were found in the K and α-angle values at all postoperative assessment points compared to day 0. Our study suggests that clopidogrel may reduce post-operative thrombocytosis and hypercoagulability in dogs that undergo splenectomy for splenic masses.

Immune-mediated hemolytic anemia and pure red cell aplasia in a Jack Russell Terrier during treatment for hypoadrenocorticism

An 11-year-old neutered male Jack Russell Terrier was presented to Yuki Animal Hospital for regenerative anemia during the treatment of hypoadrenocorticism. A blood smear examination showed spherocytes, polychromatic erythrocytes, and erythrocyte ghosts. The direct agglutination test was positive at 37°C. The dog was then diagnosed with immune-mediated hemolytic anemia (IMHA). Although prednisolone and mycophenolate mofetil were administered, the hematocrit and reticulocyte count decreased, and nonregenerative anemia developed. A bone marrow examination was performed to diagnose the cause of the nonregenerative anemia. Histologic and cytologic bone marrow examination revealed a normocellular to hypercellular medulla with severe erythroid hypoplasia. No proliferation of lymphocytes or lymphoblast-appearing cells was observed. This dog was diagnosed with pure red cell aplasia (PRCA). Despite treatment with immunosuppressive agents, the patient died of thrombosis. Although these associations were unclear, this is the first report of PRCA diagnosis following IMHA and while treating hypoadrenocorticism.

Evaluation of thrombin generation in dogs administered clopidogrel

Introduction

The antiplatelet effect of clopidogrel can vary between patients. A modified thromboelastography (TEG) protocol (TEG-Platelet Mapping assay® [TEG-PM]) can be used for clopidogrel monitoring but is not widely available. Thrombin generation (TG) assays could offer a novel alternative. The main objective of this pilot study was to assess TG assay variables (lag time, peak, endogenous thrombin potential [ETP]) in dogs before and after 7 days of clopidogrel administration and compare with TEG-PM variables (maximum amplitude [MA]-ADP and percentage (%) inhibition).

Methods

Six healthy mix-breed dogs were enrolled in this pilot study. Blood samples for platelet count, TG assays, and TEG-PM were obtained at two time points, corresponding to baseline, and after 7 days of clopidogrel administration (mean 2.3 +/- 0.3 mg/kg PO q24 hours). Data were then compared with a Student's t-test.

Results

There was no significant change in TG assay variables performed on platelet poor plasma after 7 days of clopidogrel administration: lag time (Day 1: 1.8 +/- 0.2 min, Day 7: 1.8 +/- 0.2 min, p = 0.42); peak (Day 1: 76 +/- 7 nM, Day 7: 72 +/- 10 nM, p = 0.49); and ETP (Day 1: 399 +/- 27 nM*min, Day 7: 392 +/- 32 nM*min; p = 0.49). There were significant changes in TEG MA-ADP (Day 1: 19 +/- 8 mm, Day 7: 9 +/- 6 mm, p = 0.04) and % inhibition (Day 1: 58 +/- 27, Day 7: 99 +/- 0.3, p = 0.02).

Discussion

Clopidogrel administration did not lead to changes in TG assay variables performed on platelet poor plasma samples, despite concomitant changes in TEG-PM variables consistent with platelet inhibition. Based on this pilot study, thrombin generation performed on platelet poor plasma may not be a useful antiplatelet monitoring tool in dogs.

Right atrial thrombus formation in a dog after successful electrical cardioversion for atrial fibrillation

Right atrial masses in dogs are commonly diagnosed as malignant tumors. This report describes a dog with a right atrial mass that appeared after successful electrical cardioversion of atrial fibrillation and resolved with antithrombotic treatment. A 9-year-old mastiff was presented for acute vomiting, and occasional cough of several weeks' duration. Ultrasonographic and radiographic examinations of the abdomen and chest identified mechanical ileus, as well as pleural effusion and pulmonary edema, respectively. Echocardiography indicated a dilated cardiomyopathy phenotype. During anesthetic induction for laparotomy, atrial fibrillation developed. Electrical cardioversion successfully restored sinus rhythm. An echocardiogram performed 2 weeks later disclosed a right atrial mass, which had not been apparent before cardioversion. Repeat echocardiography after 2 months of clopidogrel and enoxaparin treatment failed to detect the mass. Intra-atrial thrombus formation is possible after successful cardioversion of atrial fibrillation and should be considered as a differential diagnosis for echocardiographically detected atrial masses.

Coagulation Abnormalities in Dogs with Parvoviral Enteritis

Hemostatic alterations have been documented in dogs with canine parvoviral enteritis. This study's aims were to measure the standard coagulation parameters, and to assess the relationship between them and the clinical variables in dogs with canine parvoviral enteritis. Nine client-owned dogs with a canine parvoviral infection were included in a prospective, observational clinical study. Clinical score and coagulation status were assessed at admission. All nine dogs showed alterations of three or more standard coagulation variables. A correlation analysis evidenced a significantly high positive correlation between the activated partial thromboplastin time and clinical score. The present study concurs that dogs with canine parvoviral enteritis have coagulation disorders that are detectable by measuring the standard coagulation parameters.

Coagulation status, fibrinolysis, and platelet dynamics in dogs with chronic inflammatory enteropathy

Background

Coagulation status is poorly understood in dogs with chronic inflammatory enteropathy (CIE). Fibrinolytic activity and platelet dynamics have not been evaluated in CIE dogs.

Objectives

To assess coagulation status and fibrinolysis in normoalbuminemic CIE dogs (CIE‐N) and CIE dogs with protein‐losing enteropathy (CIE‐PLE) compared to healthy controls (HC). To evaluate thromboelastography (TEG) variable differences between groups and for correlations with clinicopathologic data. To report platelet dynamics in CIE dogs.

Animals

Twenty‐five client‐owned dogs with CIE (n = 16 CIE‐N; n = 9 CIE‐PLE); 14 HC beagle dogs.

Methods

All dogs had tissue factor + tissue plasminogen activator TEG. Nine of 25 CIE dogs had whole blood impedance platelet aggregometry. The TEG variables and coagulation data were compared between all CIE vs HC dogs, CIE‐N dogs vs HC, and CIE‐PLE dogs vs HC. Clinicopathologic and coagulation data were available for CIE dogs and assessed for correlation to TEG variables.

Results

Dogs with CIE had higher maximum amplitude (MA; P < .001), longer clot lysis times (CLTs; P < .001), lower % lysis after 30 minutes (LY30; P < .001), and % lysis after 60 minutes (LY60; P < .001) compared to HC, suggesting hypercoagulability and hypofibrinolysis. When separated out, both CIE‐N and CIE‐PLE dogs had higher MA, longer CLT, and lower LY30 and LY60 compared to HC. Serum albumin and 25‐hydroxyvitamin D (25[OH]D) concentrations, and plasma antithrombin and fibrinogen concentrations moderately correlated with MA.

Conclusions and Clinical Importance

Normoalbuminemic and hypoalbuminemic CIE dogs were considered hypercoagulable based on TEG compared to HC. Some CIE dogs displayed hypofibrinolytic phenotypes on TEG.

Therapeutic Strategies for Treatment of Immune-Mediated Hemolytic Anemia

Immune-mediated hemolytic anemia is a common hematologic disorder in dogs. Disease management involves immunosuppression using glucocorticoids, potentially in combination with other medications such as azathioprine, cyclosporine, or mycophenolate mofetil. Therapeutic drug monitoring may enhance the utility and maximize the safety of cyclosporine and mycophenolate mofetil. The disease is proinflammatory and prothrombotic. Antithrombotic drug administration is therefore essential, and anticoagulant therapy should be initiated at the time of diagnosis. Additional therapies include red blood cell transfusion to support blood oxygen content. Future therapies may include therapeutic plasma exchange, anti-CD20 monoclonal antibodies, and complement inhibitors.

Comparison of the prothrombin time-derived and Clauss assays for the measurement of plasma fibrinogen in hospitalized dogs

BACKGROUND

Accurate measurement of fibrinogen is necessary for detecting bleeding tendencies and inflammation. The Clauss assay determines fibrinogen concentration from its inverse relationship with thrombin-induced clot times. PT-derived assays determine fibrinogen concentrations from changes in the optical density during a routine prothrombin assay and allow determination of fibrinogen without additional reagents. This method has not been assessed in clinically ill dogs.

OBJECTIVES

We aimed to determine the agreement between the Clauss and PT-derived fibrinogen assays and compare the ability of the assays to predict surgery-associated transfusions and discriminate between dogs with and without bleeding.

METHODS

Retrospective medical record review identified 200 dogs with a variety of underlying diseases with results from both assays. The two assays were compared using Passing-Bablok regression, and the ability of the assays to identify bleeding and predict the need for transfusions was assessed with receiver operating characteristic (ROC) curve analyses.

RESULTS

The PT-derived assay displayed constant (y-intercept, 32 mg/dL; 95% CI 18-41) and proportional (slope, 0.79; 95% CI 0.75-0.82) bias compared with the Clauss assay. The Clauss assay reported lower values than the PT-derived assay at lower fibrinogen concentrations and higher values at higher concentrations. Comparing the area under the ROC curve did not detect significant differences in the ability of the two assays to discriminate between dogs with and without bleeding or predict the need for surgery-associated transfusions.

CONCLUSIONS

The PT-derived and Clauss assays are not interchangeable, and the Clauss assay could be more sensitive to hypofibrinogenemia in dogs.

Haemostatic, fibrinolytic and inflammatory profiles in West Highland white terriers with canine idiopathic pulmonary fibrosis and controls

BACKGROUND

Canine idiopathic pulmonary fibrosis (CIPF) is a progressive interstitial lung disease mainly affecting old West Highland white terriers (WHWTs). The aetiology of CIPF is currently unknown and pathogenesis poorly understood. A genetic basis is strongly suspected based on the breed predisposition. CIPF shares clinical and pathological features with human IPF. In human IPF, coagulation disorders favouring a local and systemic pro-thrombotic state have been demonstrated in association with disease severity and outcome. The aim of this study was to compare the systemic haemostatic, fibrinolytic and inflammatory profiles of WHWTs affected with CIPF with breed-matched controls (CTRLs). Additionally, data collected in both groups were interpreted with regard to the reference intervals (when available) to assess possible pro-thrombotic features of the WHWT breed that may be related to CIPF predisposition. A total of 14 WHWTs affected with CIPF and 20 CTRLs were included.

RESULTS

WHWTs affected with CIPF had prolonged activated partial thromboplastine time in comparison with CTRLs (12.2 ± 0.9 s vs. 11.5 ± 0.7 s, P = 0.028), whereas results obtained in both groups were all within reference ranges. There was no significant difference between groups for the other factors assessed including plasmatic concentrations of fibrinogen, D-dimers concentration, antithrombin III activity, protein S and protein C activities, anti-factor Xa activity, activated protein C ratio, serum C-reactive protein concentration, and rotational thromboelastometry indices. Platelet count and plasmatic fibrinogen concentration were found to be above the upper limit of the reference range in almost half of the WHWTs included, independently of the disease status.

CONCLUSIONS

Results of this study provide no clear evidence of an altered systemic haemostatic, fibrinolytic or inflammatory state in WHWTs affected with CIPF compared with CTRLs. The higher platelet counts and fibrinogen concentrations found in the WHWT breed may serve as predisposing factors for CIPF or simply reflect biological variation in this breed.

Clinical application of the American College of Veterinary Emergency and Critical Care (ACVECC) Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines to small animal cases

OBJECTIVE

To illustrate the application of the Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines to the management of dogs and cats at risk of developing thrombosis using a case-based approach.

ETIOLOGY

Dogs and cats become at risk of developing thrombosis from a wide range of conditions. These conditions often involve a specific insult followed by an inflammatory response and when combined with other contributing factors (eg, hypercoagulability, vascular endothelial injury, hemodynamic changes) create favorable conditions for thrombosis.

DIAGNOSIS

Development of thrombosis in small animals remains challenging to demonstrate. Compatible clinical signs, the presence of known risk factors, and supporting diagnostic tests may be highly suggestive of the development of thrombosis.

THERAPY

Therapeutic recommendations in accordance with the CURATIVE guidelines for dogs and cats are described in specific case vignettes presented. Discussion is centered on antithrombotic drug choices and dosing protocols, as outlined in Domains 2 and 3 of the CURATIVE guidelines. Where appropriate, guidelines related to therapeutic monitoring (Domain 4) and discontinuation of antithrombotics (Domain 5) were included.

PROGNOSIS

In small animals at risk of developing thrombosis, overall prognosis may be improved by following consensus-based recommendations on the use of antithrombotics as outlined in the CURATIVE guidelines. Whether such interventions have any impact on outcome requires further investigation.

Global hemostasis in healthy bitches during pregnancy and at different estrous cycle stages: Evaluation of routine hemostatic tests and thromboelastometry

This study assessed the global hemostasis (including prothrombin time [PT], activated partial thromboplastin time [aPTT], antithrombin activity [ATA], fibrinogen and d-Dimer concentrations, platelet count, plateletcrit and thromboelastometry) in healthy pregnant bitches, comparing the results with those of healthy bitches at different estrous cycle stages, and assessed whether hemostatic changes during pregnancy are associated with serum progesterone concentration or the presence of fetuses in utero. The results show that pregnant bitches have higher fibrinogen concentration, platelet count and platelatecrit, and that fibrin and global clot formations occur faster than in non-pregnant bitches at different estrous cycle stages. Additionally, clot strength was higher in pregnant bitches than in non-pregnant ones. There were no differences in PT, ATA, and D-dimer concentration between all study groups. The aPTT was significantly shorter in bitches at the fourth and last pregnancy weeks, compared to the anestrus group, and shorter in both the fourth and last pregnancy weeks groups, compared to diestrus group. These results all support a hypercoagulable state in healthy pregnant bitches, unassociated with progesterone concentration.