Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 4-Refining and monitoring antithrombotic therapies

Comparison of coagulation and fibrinolysis in Irish Wolfhounds and age-matched control dogs using tissue plasminogen activator-augmented viscoelastic testing

OBJECTIVE

To determine if Irish Wolfhounds (IWs), like other sighthounds, are hyperfibrinolytic compared with nonsighthound dogs using 2 native and tissue plasminogen activator (tPA)-enhanced viscoelastic assays, one that is whole blood-based (viscoelastic coagulation monitor [VCM]) and the other that is plasma-based thromboelastography (TEG).

DESIGN

Cohort study.

SETTING

University teaching hospital.

ANIMALS

A convenience sample of 27 IWs recruited from the Irish Wolfhound Association of New England Specialty and the local community, and 27 healthy, age-matched, large-breed control dogs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood samples including CBC, biochemistry, traditional coagulation, and viscoelastic testing were collected from IWs and control dogs. Twelve IWs had viscoelastic testing. IWs had lower fibrinogen concentrations (215.5 ± 57.8 vs 251.4 ± 64.5 mg/dL, P = 0.034) and formed weaker clots on both whole-blood VCM and plasma TEG assays (maximum clot firmness [VCM-MCF] = 39.4 [25.1-48.8] vs 48.5 [34.6-57.3], P = 0.0042; maximum amplitude [TEG-MA] = 22.7 [14.7-33.6] vs 32.2 [26.9-42.0], P < 0.0001). IWs were hyperfibrinolytic compared with control dogs on VCM whole-blood assays, with 25 U/mL tPA (lysis at 30 min [VCM-LI30] = 68.1 [0-100] vs\ 99.9 [63.3-100], P = 0.0009; lysis at 45 min [VCM-LI45] = 31.0 [0-100] vs 98.1 [38.4-100], P = 0.0002) but hypofibrinolytic compared with controls on TEG plasma assays with 50 U/mL tPA (lysis at 30 min [TEG-LY30] = 45.7 [4.6-94.6] vs 93.7 [12.3-96.5], P = 0.0004; lysis at 60 min [TEG-LY60] = 68.7 [29.7-96.8] vs 95.7 [34.4-97.6], P = 0.0003). Minimal fibrinolysis was measured on whole-blood VCM or plasma TEG assays without the addition of tPA, and there were no differences between the 2 groups.

CONCLUSIONS

Weaker clots were found in IWs than control dogs. With the addition of tPA, IWs had evidence of hyperfibrinolysis on whole-blood VCM assays and hypofibrinolysis on plasma TEG assays compared with control dogs. Without the addition of tPA, however, both groups of dogs showed minimal fibrinolysis on viscoelastic testing.

Case report: Severe hepatopathy following rivaroxaban administration in a dog

Rivaroxaban, a specific factor Xa inhibitor and commonly utilized anticoagulant, has been known to cause hepatotoxicity and liver failure in humans. Although rivaroxaban is frequently used in veterinary medicine, hepatotoxicity has not been previously reported in dogs. The current case report describes a dog that developed severe hepatopathy following rivaroxaban administration for a large right pulmonary artery thrombus. An estimated 6-year-old spayed female mixed-breed dog developed anorexia and lethargy 9 days after rivaroxaban administration began. Subsequent labwork revealed severe hepatocellular hepatopathy, and rivaroxaban was discontinued. Additional diagnostics did not reveal an underlying etiology, although hepatic cytology could be consistent with a toxic injury. The hepatopathy and clinical signs improved after rivaroxaban was discontinued. The time to onset, type of hepatopathy, and time to resolution were all similar to those reported for human cases. This case provides precedence to advocate for improved and closer monitoring of dogs receiving factor Xa inhibitors. In cases of suspected hepatotoxicity with no other identifiable cause, a risk-benefit analysis should be performed, and discontinuation of rivaroxaban administration or alternative anticoagulant medications should be considered.

Rivaroxaban versus enoxaparin plus clopidogrel therapy for hypertrophic cardiomyopathy-associated thromboembolism in cats

Background and Aim

Cardiogenic embolism (CE) is a common complication of feline hypertrophic cardiomyopathy (HCM), leading to severe clinical symptoms. This study compared the effects of rivaroxaban and enoxaparin combined with clopidogrel on cats.

Materials and Methods

This was a single-center, prospective, randomized controlled trial. In this study, rivaroxaban or enoxaparin plus clopidogrel was prescribed to 23 cats for at least one of the following events: Abnormal movement of the anterior mitral leaflet during systole, enlargement of the left atrium, spontaneous echocardiographic contrast, or presence of arterial thromboembolism. Oral rivaroxaban (2.5 mg, q24 h) was prescribed to six cats. Subcutaneous injections of enoxaparin (1 mg/kg, q24 h) plus oral clopidogrel (3 mg/kg, PO q24 h) for 60 days were administered to 17 cats. Renal insufficiency and bleeding complications were observed. Plasma concentrations of D-dimer, prothrombin time (PT), partial thromboplastin time, and international normalized ratio (INR) were evaluated. We analyzed the relationship between echocardiography parameters and the effects of coagulation. Blood samples were collected from all cats at baseline and at 1 and 2 months post-treatment.

Results

Rivaroxaban alone and in combination with enoxaparin and clopidogrel significantly affected PT and INR. In cats treated with 2.5 mg/kg rivaroxaban for 60 days, no bleeding or recurrence of thrombus formation was observed. These data support the use of rivaroxaban for the treatment of HCM-associated thromboembolism in cats.

Conclusion

Treatment of HCM-associated thromboembolism with rivaroxaban alone demonstrated clinical effectiveness with no clinical complications in cats.

Investigation of Platelet Function Analyzer 200 platelet function measurements in healthy cats and cats receiving clopidogrel

The Platelet Function Analyzer 200 (PFA-200; Siemens) is an in vitro substitute for in vivo bleeding time that is designed to investigate platelet function in a more physiologic manner than traditional aggregometry. The analyzer reports a closure time (CT) as a marker of platelet function, and may also report the calculated platelet function measurement primary hemostasis components, PHC1 and PHC2. These incorporate the measured total volume (TV) of blood aspirated and the initial flow rate (IF). We determined, for the COL/ADP and P2Y cartridges, the median total volume (TVmedian), and RIs for CT, IF, TV, PHC1, and PHC2, and investigated the sensitivity and specificity of those parameters at the determined interpretation thresholds in determination of the clopidogrel effect. Healthy client-owned cats were recruited prospectively to determine RIs for CT, IF, TV, PHC1, and PHC2. Healthy blood-donor cats and cats on clopidogrel therapy were included retrospectively to determine test performance. In 20 healthy cats, RIs for COL/ADP were CT (19.5-87.2 s), IF (199-278 µL/min), TV (199-332 µL), PHC1 (94-106%), and PHC2 (52-148%); and for P2Y, CT (4.2-94.3 s), IF (112-208 µL/min), TV (151-294 µL), PHC1 (35-178%), and PHC2 (90-109%). CVs were calculated for all of these values. Specificity for detection of the clopidogrel effect was calculated from a group of healthy blood donors, and sensitivity for detection of the clopidogrel effect from a group of cats with known clopidogrel effect. Sensitivity and specificity were, for COL/ADP: CT (83.3%, 66.6%), IF (41.4%, 83.3%), TV (83.3%, 100%), PHC1 (100%, 100%) and PHC2 (100%, 83.3%); and for P2Y: CT (100%, 94.4%), IF (30%, 44.4%), TV (100%, 94.4%), PHC1 (100%, 100%), and PHC2 (100%, 97.7%). These PFA-200 values may be beneficial in the determination of platelet function in cats.

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.

Retrospective analysis of immunosuppressive and anti-thrombotic protocols in nonassociative immune mediated hemolytic anemia in dogs

BACKGROUND

Evidence supporting the effectiveness of therapeutic protocols for nonassociative immune-mediated hemolytic anemia (na-IMHA) is weak.

HYPOTHESIS/OBJECTIVES

Investigate the efficacy of various drugs in na-IMHA.

ANIMALS

Two hundred forty-two dogs.

METHODS

Multi-institutional retrospective study (2015-2020). Immunosuppressive effectiveness was determined by time to packed cell volume (PCV) stabilization and duration of hospitalization through analysis by mixed model linear regression. Occurrence of disease relapse, death, and antithrombotic effectiveness, were analyzed using mixed model logistic regression.

RESULTS

Use of corticosteroids vs a multi-agent protocol had no effect on time to PCV stabilization (P = .55), duration of hospitalization (P = .13), or case fatality (P = .06). A higher rate of relapse (P = .04; odds ratio: 3.97; 95% confidence interval [CI]: 1.06-14.8) was detected in dogs receiving corticosteroids (11.3%) during follow-up (median: 28.5 days, range: 0-1631 days) compared to multiple agents (3.1%) during follow up (median: 47.0 days, range: 0-1992 days). When comparing drug protocols, there was no effect on time to PCV stabilization (P = .31), relapse (P = .44), or case fatality (P = .08). Duration of hospitalization was longer, by 1.8 days (95% CI: 0.39-3.28 days), for the corticosteroid with mycophenolate mofetil group (P = .01) compared to corticosteroids alone. Use of clopidogrel vs multiple agents had no effect on development of thromboses (P ≥ .36).

CONCLUSIONS AND CLINICAL IMPORTANCE

Addition of a second immunosuppressive agent did not alter immediate outcome measures but might be associated with a reduction in relapse. Use of multiple antithrombotic agents did not reduce incidence of thrombosis.

Effects of a single subcutaneous dose of enoxaparin on veterinary viscoelastic coagulation monitor variables in healthy cats: Double blind, placebo controlled cross-over trial

BACKGROUND

Cats placed on anticoagulant medication require frequent monitoring. The veterinary viscoelastic coagulation monitor (VCM-Vet) could provide a convenient and cost-effective monitoring, enabling therapeutic decision making.

HYPOTHESIS/OBJECTIVES

Enoxaparin will lead to changes in VCM-Vet variables and these will correlate with antiXa activity.

ANIMALS

Twenty-one healthy cats.

METHODS

Cats were randomized to receive either enoxaparin (1 mg/kg) subcutaneously or 0.9% NaCl (equal volume) and crossed over with a 7-day washout period. The investigators were blinded to group allocation until data analysis. Jugular blood samples were drawn at time 0, and 2, 4, and 8 hours after injection for VCM-Vet analysis within 2 min of collection. Citrated plasma was frozen at -80°C for antiXa activity analysis. A Generalized Linear Model was completed to assess changes between baseline measurements and all time points.

RESULTS

Significant differences between the enoxaparin-treated cats and controls at for T0h and T2h were found and presented as mean ± SD for clotting time (enoxaparin, 593.4 ± 78.0 s; control, 448.5 ± 50.3 s, P < .001), clot formation time (enoxaparin, 183.1 ± 41.7 s; control, 155.4 ± 28.0 s, P = .001), and alpha angle (enoxaparin, 52.4 ± 6.1°; control, 56.9 ± 3.7 s, P = .003). AntiXa activity was significantly different between T0 and all other timepoints for the enoxaparin group (P < .001). There was no correlation between changes in clotting time and antiXa activity.

CONCLUSIONS AND CLINICAL IMPORTANCE

The VCM-Vet detects a difference at 2 hours after single-dose enoxaparin administration and it can be useful for anticoagulant therapy monitoring in cats.

Retrospective Evaluation of Intravenous Enoxaparin Administration in Feline Arterial Thromboembolism

Simple Summary

Feline arterial thromboembolism is a painful disease characterized by acute ischemic necrosis of one or more limbs due to cardiac diseases, hyperthyroidism, or neoplasia. Among others, medical treatment consists of preventing new thrombus formation primarily using heparin products, such as enoxaparin. This retrospective study reports clinical data, regain of perfusion, short-term outcome, and complications of 36 affected cats treated with a novel intravenous enoxaparin protocol. Furthermore, we aimed to report monitoring and management of the intravenous enoxaparin treatment for this disease. In our population, visible hemorrhage was rare. The most common causes of death/euthanasia were cardiac instability, acute kidney injury, neurological abnormalities, and limb necrosis. The hospital discharge rate was 47% overall and was significantly different between single limb (83%) and dual limb (29%) thromboembolism. Our study supports the intravenous use of enoxaparin in combination with oral clopidogrel for cats with thromboembolism as an alternative treatment method.

Abstract

Induction of a hypocoagulable state is imperative in the treatment of feline arterial thromboembolism. Publications in human medicine report the use of enoxaparin intravenously in selected cases. The aim of our retrospective study was to report the regain of perfusion, short-term outcome, and complications of cats treated with a novel intravenous enoxaparin protocol (1 mg/kg bolus injection followed by 3 mg/kg/day continuous infusion) combined with oral clopidogrel administration. The secondary aim was to report the monitoring of enoxaparin with anti-Xa activity. There were 36 cats included. The probability of reaching limb reperfusion was significantly (p = 0.0148) higher with anti-Xa activity within or above the target range compared to results below the target range (19/21, 90% versus 11/20, 55%). The complications observed were acute kidney injury (15/36, 42%), hemorrhage (2/36, 6%), and neurological signs (6/36, 17%). The most common causes of death/euthanasia were cardiac instability, acute kidney injury, neurological abnormalities, and limb necrosis. The hospital discharge rate was 83% (10/12) for single limb and 29% (7/24) for dual limb thrombosis; the difference was significant (p = 0.0039). The median hospitalization time for the survivors was 119.5 (95–480) h. Our study supports the use of intravenous continuous rate infusion of enoxaparin in combination with oral clopidogrel for cats with aortic thromboembolism. We report similar discharge rates and lower hemorrhage rates than previously reported with thrombolytic treatment.

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.

Life-Threatening Mediastinal Hematoma Formation After Removal of the Hemodialysis Catheter in a Boxer: A Case Report

A 4-year-old female Boxer was referred for renal replacement therapy 2 days after observed grape ingestion. An 11-French dual-lumen dialysis catheter was placed into the right jugular vein and continuous renal replacement therapy was initiated for 66 h. Afterwards the patient received enoxaparin subcutaneously as a thromboprophylaxis. Four hours after removal of the dialysis catheter the patient developed severe dyspnea with hypercapnia and signs of hemorrhagic shock. Bedside ultrasound and X-rays of the thorax revealed a soft tissue opacity dorsally of the trachea, located in the mediastinum. The findings were consistent with mediastinal bleeding and hematoma formation. Blood gas examination indicated hypoventilation. The dog was managed conservatively with multiple blood transfusions and mechanical ventilation. The patient survived to discharge, and the hematoma was fully absorbed in the radiographs after 17 days. Patients with impaired kidney function should receive individualized enoxaparin dosage adjusted to anti-Xa levels and should be strictly monitored for complications. Mediastinal hemorrhage and hematoma formation should be considered as a potential complication in patients receiving a jugular vein catheter.

Warfarin-induced major unilateral breast necrosis in a patient with antiphospholipid syndrome: A case report

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Warfarin rarely causes necrosis, and antiphospholipid syndrome is a rarer cause of skin necrosis. Physicians should consider both conditions in the aetiology of skin necrosis.

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Management should involve stopping warfarin treatment, administering alternative medications, taking a good history, and performing proper examination, investigation, and wound management with dressings or operation using a multidisciplinary team.

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Wound management depends on the patient’s medical condition and considers the reconstructive ladder.

Introduction

Warfarin-induced necrosis is a rare complication associated with the use of warfarin in addition to antiphospholipid syndrome.

Case presentation

A 50-year-old female patient with a known case of antiphospholipid syndrome started warfarin treatment for ischaemic changes in her toes and subsequently experienced warfarin-induced necrosis in her left breast. Then, warfarin treatment was suspended, and she was started on enoxaparin. Debridement was performed, and a skin graft was applied without complications.

Discussion

Skin necrosis has many differential diagnoses, and physicians must take a proper history and perform a physical examination with proper investigations involving a multidisciplinary team, including plastic surgery, haematology, internal medicine, and wound care specialists. Plastic surgery offers many options for reconstruction depending on the patient’s medical condition, the size of the wound and the location following the reconstructive ladder.

Conclusion

This case report presents a rare complication of warfarin in the context of antiphospholipid syndrome and describes the management of unilateral breast necrosis. Physicians should be highly suspicious of this condition in patients with skin necrosis who were administered warfarin or have antiphospholipid syndrome.

The Rare Occurrence of a Left Atrial Thrombus in a Dog

Intracardiac thrombi are rare in dogs. If they occur, they are mostly seen in the right atrium while only two case reports describing a mural left atrial thrombus in dogs are available. This case report describes a 14-year-old mixed-breed bitch that was presented at the clinic because of dyspnoea. The dog suffered from alopecia for about three years and displayed polyuria and polydipsia for a number of months. Clinical examination revealed intensified inspiratory and expiratory respiratory sounds and various heart sounds. Chest X-ray showed cardiomegaly (VHS 11) and a mixed bronchoalveolar lung pattern of the caudal lung. A transthoracic echocardiography was performed and showed a moderate mitral regurgitation, a highly dilated left atrium, a low-grade pulmonary insufficiency, and a minimal aortic and tricuspid insufficiency. Additionally, a free-floating ball thrombus was found in the left atrium. Hyperadrenocorticism was indicated by an ACTH stimulation test. The previous medical therapy of the referring veterinarian consisted of benazepril and furosemide and was complemented by clopidogrel. The pet owners declined any further clinical diagnostics and therapy. The dog died 19 days later. This is the first reported case of a dog with a free-floating left atrial thrombus. Specific therapeutic strategies for intracardiac thrombi in the dog are currently not available, and therefore, every patient should be treated individually.

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.

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.

Use of rivaroxaban for treatment of cranial vena cava syndrome secondary to transvenous pacemaker lead thrombosis in a dog

A six-year-old Brussels griffon was presented for cervical swelling three months after implantation of a transvenous pacemaker. Transthoracic echocardiography demonstrated a thrombus associated with the pacemaker lead, partially obstructing right atrial inflow. The laboratory findings were consistent with protein-losing nephropathy. Initial medical therapy consisted of rivaroxaban (0.68 mg/kg orally every 24 hours), clopidogrel (2.5 mg/kg orally every 24 hours), and enalapril (0.5 mg/kg orally every 12 hours). Resolution of cervical and thoracic edema was noted within two weeks of initiating therapy. Recheck echocardiography two months and one year later revealed decreasing thrombus size despite worsening proteinuria. To the authors' knowledge, this is the first documented use of rivaroxaban for successful medical treatment of cranial vena cava syndrome caused by intracardiac pacemaker lead thrombosis in a hypercoagulable patient.

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.