Serial haemostatic monitoring of dogs with multicentric lymphoma

Lymphoma is the most common haematopoietic malignancy in dogs and it has been associated with hypercoagulability and subsequent thromboembolism. The objectives of this study were to serially characterize the haemostatic status of dogs with multicentric lymphoma. Thromboelastography, thrombin–antithrombin complex concentration and routine haematology and coagulation panels were measured. Twenty‐seven dogs were included in the study and 15 completed the study in remission. At presentation, 81% (22/27) of dogs with multicentric lymphoma had altered haemostatic profiles consistent with hypercoagulability. Laboratory evidence of hypercoagulability did not resolve during treatment or for up to 1 month following attainment of clinical remission. Accelerated rate of clot formation at the time of chemotherapeutic protocol completion was associated with decreased survival time. We concluded that dogs with multicentric lymphoma were frequently hypercoagulable from presentation through 4 weeks after the completion of chemotherapy. Increased angle and shortened K in dogs that have successfully completed their chemotherapeutic protocol may be associated with shorter survival times.     

Use of thromboelastography in dogs with immune-mediated hemolytic anemia: 39 cases (2000–2008)

Objective – To analyze thromboelastograms (TEGs) of naturally occurring cases of immune-mediated hemolytic anemia (IMHA) in order to identify whether a hypercoagulable state was present and whether its presence was associated with differences in survival.
Design – Retrospective study spanning January 2000 to June 2008. Medical records of dogs were evaluated. Endpoints were considered death or discharge from the hospital.
Setting – Academic teaching hospital.
Animals – Thirty-nine dogs with a diagnosis of IMHA and at least one TEG performed during hospitalization were included.
Interventions – None.
Measurements and Main Results – Four values were evaluated from the TEG: the R time (R), K time (K), alpha angle (α), and maximum amplitude. From these values, a coagulation index (CI) was calculated to classify patients as normocoagulable, hypercoagulable, or hypocoagulable. Thirty-three of 39 patients were hypercoagulable based on the CI. The 6 remaining dogs were normocoagulable. The patients with a normocoagulable CI had an increased mortality rate (100%) when compared with the hypercoagulable patients using Fisher's exact test ( P =0.02). Additionally, prolongation of partial thromboplastin time did not preclude hypercoagulable TEG values.
Conclusions – The majority of dogs with IMHA were hypercoagulable as measured by TEG. A normal CI was associated with a worse outcome in this patient population. TEG may provide additional and complementary information to prothrombin time and partial thromboplastin time relating to coagulation status in dogs with IMHA and may help predict prognosis and potentially guide clinical decisions to utilize anticoagulant drugs.     

The effect of unfractionated heparin on thrombelastographic analysis in healthy dogs

Objective – To determine the effect of single and multiple doses of SQ heparin (200 U/kg) on the thrombelastogram of healthy dogs. Design – Prospective study. Setting – University research facility. Animals – Six random‐source female dogs. Interventions – Baseline parameters, including a CBC with platelet count, prothrombin time, activated partial thromboplastin time (aPTT), and antithrombin were performed. Thrombelastography (TEG) and aPTT were performed hourly for 12 hours after unfractionated heparin dosing (200 U/kg, SQ). Anti‐Xa activity was assayed at 0, 3, 6, and 8 hours. Heparin was then administered every 8 hours for 3 days. The sampling protocol on Day 4 was identical to Day 1. Measurements and Main Results – On Day 1, percentage change from baseline for TEG parameter R, as well as absolute values of K, angle, and maximum amplitude (MA) were evaluated. Statistically significant (P<0.01) prolongation of the R time and a decrease in angle and MA was seen in all dogs by hour 3. R and MA were unmeasurable for most dogs between 3 and 5 hours. All TEG tracings returned to baseline by 12 hours. Day 4 TEG tracings mimicked those on Day 1. Only 1 dog achieved aPTT values outside the reference interval on both days. Anti‐Xa activity levels increased on Day 4 but not on Day 1. Based on post hoc in vitro analysis, prolongation of R time occurred at plasma heparin levels as low as 0.075 U/mL, well below the lower limit of detection of the anti‐Xa activity level assay. Conclusions – Administration of SQ heparin results in progressive changes in the TEG tracing, with maximal change occurring 3–5 hours after dosing. The extensive prolongation of the R time also indicates that TEG may be too sensitive and limits its utility as a monitoring tool for unfractionated heparin therapy.     

Monitoring unfractionated heparin therapy in dogs by measuring thrombin generation

Background: The calibrated automated thrombogram (CAT), an assay that permits measurement of thrombin generation in plasma, may be useful in studying hemostatic disorders and anticoagulant therapy in animals. Objectives: The aims of the study were to measure thrombin generation in healthy Beagle dogs and to evaluate the potential use of the CAT assay for monitoring therapy with unfractionated heparin (UFH). Methods: Individual platelet‐poor plasma samples and a plasma pool from 20 healthy adult Beagles were prepared. Serial UFH plasma dilutions were used to establish an in vitro heparin‐sensitivity curve. The pharmacodynamic effects of heparin in vivo were evaluated in Beagles using the CAT assay to measure thrombin generation with tissue factor at a concentration of 5 pM for initiation. Results: In healthy Beagles, the range of endogenous thrombin potential (ETP) was 238.7–414.0 nM/min (mean ± SD, 340.4 ± 63.1 nM/min). ETP intra‐assay and interassay variations were 7.1% and 12.9%, respectively. In vitro, a UFH concentration ≥0.4 U/mL resulted in total inhibition of thrombin generation. In vivo, the maximal effect of UFH on ETP was observed at 170 ± 36 minutes (range, 120–210 minutes) and resulted in a decrease in ETP of 38.5 ± 7.8% (range, 26.5–50.3%). In 210–420 minutes, ETP returned to baseline in 5 dogs. Conclusion: Our study demonstrates that thrombin generation can be measured in canine plasma and may be useful in assessing the degree of anticoagulation provided by UFH.     

Incidence of prolonged prothrombin time in dogs following gastrointestinal decontamination for acute anticoagulant rodenticide ingestion

Objective: To determine the effect of gastrointestinal (GI) decontamination on the incidence of prolonged prothrombin time (PT) in dogs after anticoagulant rodenticide ingestion. Design: Retrospective study. Setting: Urban emergency room. Animals: One hundred and fifty‐one client‐owned dogs. Measurements: Dogs presented to the emergency room within 6 hours of ingestion of an anticoagulant rodenticide and had a PT measured within 2–6 days of toxicant ingestion before initiating vitamin K therapy were included. Dogs were categorized as treated or untreated based on the institution of vitamin K therapy following PT testing. The signalment, body weight, type of rodenticide ingested, time elapsed between ingestion and initial presentation, method(s) of GI decontamination, and the times elapsed between both toxicant ingestion and initial hospital presentation until determination of PT were recorded. The PT results were recorded as well as any treatment received following the recheck examination. Any reported incidents of bleeding or untoward effects between exposure and reexamination were recorded. Main results: Of 151 dogs, only 11 dogs (8.3%) developed prolonged PT requiring vitamin K supplementation. None of the 11 dogs with prolonged PTs exhibited signs of bleeding or required transfusion therapy. No differences in age, weight, or time elapsed between treated and untreated patients were found. Conclusions: The incidence of prolonged PT is low in dogs receiving GI decontamination within 6 hours of anticoagulant rodenticide ingestion. Delaying vitamin K therapy until a PT has been assessed 48–72 hours after initial exposure appears to be safe and sensitive in dogs following anticoagulant rodenticide ingestion.     

Massive envenomation by Vespula spp. in two dogs.

Two dogs, a 5 year old golden retriever and a 5 year old yellow Labrador, were stung by numerous yellow jackets (Vespula sup.). Both dogs exhibited signs consistent with direct toxic effect of the wasp venom. The laborador was more severely affected, and was euthanized less than 24 hours after after admission. On postmorten, changes were seen that were consistent with anaphylaxis and disseminated intravascular coagulation. The golden retriever, although exhibiting respiratory distress, prolongation of coagualtion, and increased liver enzymes, eventually made a full recovery.     

Effects of oxypolygelatin and dextran 70 on hemostatic variables in dogs

Objective To evaluate and compare coagulation variables following the administration of oxypolygelatin and dextran 70 to clinically healthy dogs. Study design Randomized cross‐over experimental study. Animals A total of eight healthy adult female Beagles aged 2–4 years old and weighing 11.8 ± 2.7 kg. Methods The dogs received a 15‐minute intravenous (IV) infusion of 5 mL kg^?1 oxypolygelatin or 10 mL kg^?1 6% dextran 70. Before (PRE) and at 2, 5, and 24 hours after administration, packed cell volume (PCV), total solids concentration (TS), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration (FIB), platelet numbers (Plat), factor VIII coagulant activity (VIII:C), von Willebrand factor antigen concentration (vWf:Ag) and platelet function and buccal mucosal bleeding time (BMBT) were measured. Platelet function was assessed using aggregation and by measuring ATP release from aggregating platelets over 6 minutes, with 20, 10, and 5 µm ADP and 5 and 10 µg of collagen mL^?1 as platelet activation agonists. Results All baseline values were within our normal ranges, except for one dog that had low vWf:Ag PRE values prior to both dextran and oxypolygelatin administration. Following dextran and oxypolygelatin administration, the PCV and TP were significantly (p < 0.05) decreased. Plat, FIB, and vWf:Ag decreased, while BMBT and VIII:C increased following dextran administration. Dextran also caused a significant decrease in platelet aggregation in response to ADP. Oxypolygelatin caused a significant decrease in vWf:Ag, Plat, and FIB compared to PRE values. The total amount of ATP released, standardized to platelet number, did not vary significantly for either group at any sampling time from PRE values. No significant changes from PRE values were noted at any time in either group for PT or APTT. Conclusion At the doses administered, both dextran and oxypolygelatin can interfere with hemostatic variables in healthy dogs, but dextran's effect is more profound and prolonged when compared to oxypolygelatin. Clinical relevance Oxypolygelatin causes fewer hemostatic abnormalities when compared to dextran, making it a superior colloid for administration at the doses tested.     

Changes in the coagulation parameters in dogs with protein-losing enteropathy between before and after treatment

Protein-losing enteropathy (PLE) is known to induce hypercoagulability and resultant thromboembolism in dogs. We hypothesized that hypercoagulability would improve if remission was obtained in dogs with PLE after treatment. This study aimed to evaluate the changes in the coagulation parameters after treatment in dogs diagnosed with PLE. As coagulation parameters, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, thrombin-antithrombin complex (TAT), D-dimer, and antithrombin (AT) were measured. In addition to these parameters, rotational thromboelastometry (ROTEM), which evaluates the comprehensive coagulation and fibrinolysis reactions of whole blood, was conducted and the data of clotting time (CT), clot formation time (CFT), α angle (α), maximum clot firmness (MCF) and lysis index at 60 min (LI60) were obtained. Eleven of the 14 dogs diagnosed with PLE were classified as responders to the treatment based on the changes in their plasma albumin (ALB) concentration after treatment. Significant increase in CFT and decrease of α and MCF indicating the resolution of hypercoagulability were found after treatment in responder dogs; however, there was no significant change in the coagulation and fibrinolysis parameters other than those measured by ROTEM. This study demonstrated that the hypercoagulability detected by ROTEM was significantly improved after treatment in dogs with PLE.     

Thrombin‐activatable fibrinolysis inhibitor activity in healthy and diseased dogs

Background: In people, increased thrombin‐activatable fibrinolysis inhibitor (TAFI) antigen has been associated with increased risk of thrombosis, and decreased TAFI may contribute to bleeding diathesis. TAFI activity in dogs has been described in experimental models, but not in dogs with spontaneous disease. Objective: The aim of this study was to compare TAFI activity in healthy dogs with TAFI activity in dogs with spontaneous disease. Methods: Plasma samples from 20 clinically healthy Beagles and from 35 dogs with various diseases were analyzed using a commercial chromogenic assay that measured TAFI activity relative to activity in standardized pooled human plasma. Results: Median TAFI activity for the 20 Beagles was 46.1% (range 32.2–70.8%) compared with 62.6% (29.1–250%) for the 35 diseased dogs, and 14/35 (40%) had TAFI activities >the upper limit for controls. The highest individual activities (>225%) were in 3 dogs with malignant neoplasms and 1 dog with thrombocytopenia. For data grouped by diagnosis, median TAFI activity was 61.7% for benign neoplasia (n=5), 64.9% for malignant neoplasia (n=8), 75.5% for Angiostrongylus vasorum infection (n=4), 68.8% for bacterial sepsis (n=7), and 58.7% for miscellaneous diseases (n=11). Compared with TAFI activity in control dogs, median TAFI activity was significantly increased only in the group of dogs with bacterial sepsis. Conclusion: Bacterial sepsis was associated with significantly increased TAFI activity, and individual dogs with increased TAFI activities were found in all disease groups. The role of TAFI in the pathogenesis of hemostatic disorders in dogs and its value as a prognostic indicator deserve further investigation.     

Validation of human recombinant tissue factor-activated thromboelastography on citrated whole blood from clinically healthy dogs

BACKGROUND: Thromboelastography (TEG) is an analytical method that enables global assessment of hemostatic function in whole blood (WB) with evaluation of both plasma and cellular components of hemostasis. TEG has a largely unused potential in the diagnostic workup and monitoring of dogs with hemostatic disorders and it may be a valuable supplement to traditional coagulation parameters. OBJECTIVES: The objective of this study was to establish a clinically applicable reference interval for a TEG assay using recombinant human tissue factor (TF) as the activator on citrated WB from clinically healthy dogs and to evaluate the stability of citrated WB stored for 30 minutes (T30) and 120 minutes (T120) at room temperature (RT). Additionally, we evaluated the analytical variation in reaction time (R), clotting time (K), angle (alpha), and maximum amplitude (MA). METHODS: Blood was collected from 18 clinically healthy dogs. Duplicate TEG analyses with TF as the activator at a concentration of 1:50,000 were performed on canine citrated WB at T30 and T120. R, K, a, and MAwere analyzed. RESULTS: Mean TEG values at T30/T120 were R = 5.61/4.91 minutes, K = 4.20/3.34 minutes, alpha = 45.33/50.90 degrees , and MA = 47.96/50.19 mm. Significant differences in these values were observed after storage for T30 and T120 at RT, with a tendency towards hypercoagulability at T120. The mean coefficients of variation were low. CONCLUSIONS: Canine citrated WB can be used for TEG analysis with human recombinant TF as the activator when stored at RT for T30 or T120. At both time points, the analytical variation was low, suggesting that TEG analysis may be of value in evaluating dogs with hemostatic disorders. A fixed time point should be chosen for serial measurements.