Christian Bédard

Thrombelastography in dogs admitted to an intensive care unit

BACKGROUND Underlying conditions in dogs admitted to an intensive care unit (ICU) can cause hemostatic dysfunction. Thrombelastography (TEG) may be useful in detecting hemostatic alterations as compared with standard coagulation tests. OBJECTIVES The purpose of this study was to compare TEG results and those of standard coagulation tests in identifying hemostatic dysfunction in dogs admitted to an ICU and to investigate associations among the variables measured. METHODS Tissue factor-activated TEG analysis, d-dimer and fibrinogen concentrations, antithrombin (AT) activity, prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count were measured using standard techniques on 27 dogs admitted to ICU with a disease known to be associated with hemostatic dysfunction and in 31 clinically healthy control dogs. Results were compared between groups using nonparametric tests and kappa analysis; principal component analysis (PCA) and Spearman rank correlation were used to measure associations among variables. RESULTS Fourteen of 27 ICU dogs had abnormal TEG tracings, which were used to classify the dogs as hypercoagulable (n=11), hypocoagulable (n=3), or normocoagulable (n=13). Hypercoagulable dogs had significantly increased d-dimer (P=.03) and fibrinogen (P=.01) concentrations compared with normocoagulable dogs. In ICU dogs, positive associations were identified between maximum amplitude (MA), alpha-angle, fibrinogen concentration, and platelet count, and between PT, aPTT, and reaction time (R). Significant correlations were found between MA and fibrinogen (r(s)=.76, P<.001) and between reaction time (R) and PT (r(s)=.51, P=.003). CONCLUSIONS TEG was useful in detecting hemostatic dysfunction in dogs in an ICU. Positive associations among variables may provide insight as to how overall coagulation status reflects alterations in clot strength and coagulation time. Dogs with TEG tracings indicative of hypercoagulability are likely in procoagulant states. Future studies of the incidence of thrombotic complications in dogs with hypercoagulable TEG tracings are warranted.

N‐Acetyl‐β‐d‐Glucosaminidase Index as an Early Biomarker for Chronic Kidney Disease in Cats with Hyperthyroidism

BACKGROUND Hyperthyroid cats are at risk of developing azotemic chronic kidney disease (CKD) and diagnostic tools currently used to screen for CKD in hyperthyroid cats are either unreliable or impractical. HYPOTHESIS Urine N-acetyl-beta-D-glucosaminidase index (NAG(i)) is a good biomarker for azotemic CKD in hyperthyroid cats. ANIMALS Twenty-four newly diagnosed nonazotemic hyperthyroid cats and 10 healthy cats. METHODS All cats were evaluated for hyperthyroidism at baseline. Hyperthyroid cats were treated with methimazole and reevaluated once euthyroid. At the end of the study, cats were divided into 3 groups: healthy cats, nonazotemic, and azotemic euthyroid cats. Baseline group characteristics were compared to predict azotemic CKD. The influence of treatment on NAG(i) was evaluated. RESULTS Baseline NAG(i) was significantly different among groups (P= .004). Azotemic cats had a higher median value (13.12 U/g) when compared with healthy cats (1.38 U/g). With NAG(i) >2.76 U/g, negative and positive predictive values for development of azotemia were 77.7 and 50%, whereas the combination of a urine specific gravity (USG) <or=1.035 and T(4) >7.80 microg/dL enhanced predictive values to 88.9 and 83.3%, respectively. NAG(i) values decreased significantly over time in treated nonazotemic cats. CONCLUSIONS AND CLINICAL RELEVANCE Baseline NAG(i) did not differentiate azotemic from nonazotemic euthyroid cats. NAG(i) could be used to assess renal function during medical therapy allowing the clinician to adjust methimazole dosage accordingly. The combination of USG and T(4) could optimize identification of appropriate candidates for permanent treatment of hyperthyroidism.

Evaluation of a modified thrombelastography assay initiated with recombinant human tissue factor in clinically healthy horses

BACKGROUND Thrombelastography (TEG) is used to evaluate the viscoelastic properties of blood during clotting and provides a global assessment of hemostasis and clot lysis. TEG analysis initiated with recombinant human tissue factor (TF) has not been evaluated in clinically healthy horses. OBJECTIVES The purpose of this study was to determine whether TEG results are affected by the time elapsed between sampling and analysis (storage time) of equine blood samples and to establish a preliminary equine reference interval for a modified TEG assay, using recombinant human TF to initiate coagulation. METHODS Citrated blood samples were obtained from 20 clinically healthy adult horses. Thirteen samples were stored for 30, 60, and 120 minutes at room temperature before TEG analysis. Coagulation was initiated by adding 20 microL of CaCl(2) to 330 microL of blood and 10 microL of diluted recombinant TF for a final dilution of 1:3600. Reaction (R) and clotting (K) times, angle (alpha), and maximum amplitude (MA) were compared between time points. A preliminary reference interval (minimum-maximum values) was determined using data from all 20 horses after 30 minutes of sample storage. RESULTS There was a significant effect of storage time on R, K, and alpha but not MA. Reference intervals were: R, 3.65-6.4 minutes; K, 1.8-5.45 minutes; alpha, 33.4-66.2 degrees ; MA, 41.2-64.1 mm; lysis at 30 minutes post-MA (LY30), <2.75%; and lysis at 60 minutes post-MA (LY60), 1.55-9.5%. CONCLUSIONS TEG can be performed on equine citrated blood samples using recombinant human TF to activate clot formation. TEG parameters were significantly affected by storage time, suggesting an incomplete inhibition of coagulation in citrated blood.

Effect of prednisone administration on coagulation variables in healthy Beagle dogs

BACKGROUND Long-term corticosteroid therapy has been associated with increased risk of thrombotic disease in dogs. OBJECTIVE The purpose of this prospective study was to use thrombelastography (TEG) and thrombin generation (TG) to detect development of a hypercoagulable state in healthy Beagle dogs receiving oral prednisone. We hypothesized that administration of corticosteroids would result in a hypercoagulable profile on TEG tracings and an increase in TG. METHODS Six healthy adult Beagles from the University of Montreals research colony were used to conduct a prospective longitudinal study in which all dogs received 1 mg/kg of prednisone orally once daily for 2 weeks, followed by a 6-week washout period, and then 4 mg/kg of prednisone orally once daily for 2 weeks. TEG tracings on citrated whole blood and TG measurements on frozen-thawed platelet-poor plasma were obtained before prednisone administration (baseline), at the end of the washout period, and at the end of both corticosteroid trials. RESULTS Significant differences compared with baseline values were obtained for K, α, and MA, with tracings compatible with a hypercoagulable profile following both corticosteroid trials. There was a significant increase in endogenous thrombin potential only after low-dose (1 mg/kg) prednisone. CONCLUSION Administration of prednisone to healthy Beagles resulted in hypercoagulability as indicated by TEG tracings, whereas the effect on TG was more variable. Further studies are needed to determine the underlying mechanisms of hypercoagulability and its clinical impact.

Effects of feeding a high omega-3 fatty acids diet in dogs with naturally occurring osteoarthritis

The aim of this randomized, placebo-controlled and double-blinded trial was to compare the effect of a veterinary therapeutic diet (VTD) rich in omega-3 fatty acids (omega-3) from fish origin to a regular diet used as control (CTR) over a period of 13 weeks in dogs afflicted by naturally occurring osteoarthritis (OA). Thirty privately owned dogs were selected. Dogs had lameness confirmed by an orthopaedic examination, had stifle/hip OA and had locomotor disability based on the peak of the vertically oriented ground reaction force (PVF) measured using a force platform. At Baseline, all owners were asked to determine 2-5 activities of daily living that were the most impaired. Activities were scores (0-4) in accordance with severity using case-specific outcome measures (CSOM). The PVF was also measured. Dogs (15/group) were then randomly assigned to receive either the CTR or the VTD. The CSOM was completed twice weekly. The recording of PVF was repeated at Week 7 and 13. The VTD-fed dogs showed a significantly higher PVF at Week 7 (p < 0.001) and at Week 13 (p < 0.001) when compared to Baseline. From Baseline to Week 13, VTD-fed dogs had a mean (± SD) change in PVF recording of 3.5 ± 6.8% of body weight (%BW) compared with 0.5 ± 6.1%BW (p = 0.211) in CTR-fed dogs. This change in primary outcome was consistent with an effect size of 0.5. Conversely, dogs fed the CTR did not show significant change in PVF measurements. At the end of the study, the CSOM was significantly decreased (p = 0.047) only in VTD fed dogs. In lame OA dogs, a VTD that contains high level of omega-3 from fish origin improved the locomotor disability and the performance in activities of daily living. Such nutritional approach appears interesting for the management of OA.

Effect of Canine Hyperadrenocorticism on Coagulation Parameters

BACKGROUND Hyperadrenocorticism (HAC) has been associated with thrombotic disease in dogs. HYPOTHESIS The purpose of this study was to use thromboelastography (TEG) and measurement of thrombin generation (TG) to characterize the hypercoagulable state in dogs with HAC. We hypothesized that dogs with HAC would have a hypercoagulable profile on TEG tracings and an increase in thrombin generation as measured by endogenous thrombin potential (ETP). ANIMALS Sixteen dogs with HAC. Dogs were compared with a population of normal dogs used to obtain reference intervals. METHODS TEG tracings on citrated whole blood were obtained from 15 dogs, and TG measurements on frozen-thawed platelet-poor plasma (PPP) were obtained from 15 dogs. RESULTS For the TEG analysis, when results of individual dogs were compared with the reference interval, 12/15 dogs had at least 1 parameter associated with hypercoagulability. When the population of HAC dogs was compared with a population of healthy dogs, HAC dogs had decreases in R and K and increases in α and MA values. The ETP was increased when the HAC group was compared with a population of normal dogs. However, only 3/15 dogs had an ETP above reference interval, and 1/15 had a decreased lag time. CONCLUSION AND CLINICAL IMPORTANCE Of 16 dogs with HAC, 12/15 had evidence of hypercoagulability when evaluated by TEG, 4/15 when evaluated by TG, and 2 dogs had increases in ETP and MA.

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.

Brachystemma calycinum D. Don Effectively Reduces the Locomotor Disability in Dogs with Naturally Occurring Osteoarthritis: A Randomized Placebo-Controlled Trial

Objective. The aim of this randomized placebo-controlled trial was to evaluate the beneficial effect of a whole plant extract of Brachystemma calycinum D. Don (BCD) in naturally occurring osteoarthritis (OA) in dogs. Methods. Dogs had stifle/hip OA and poor limb loading based on the peak of the vertically oriented ground reaction force (PVF) measured using a force platform. At baseline, PVF and case-specific outcome measure of disability (CSOM) were recorded. Dogs (16 per group) were then assigned to receive BCD (200 mg/kg/day) or a placebo. The PVF was measured at week (W) 3 and W6. Locomotor activity was recorded throughout the study duration using collar-mounted accelerometer, and CSOM was assessed biweekly by the owner. Results. BCD-treated dogs had higher PVF at W3 and W6 when compared to Baseline (P < 0.001) and at W6 when compared to placebo-treated dogs (P = 0.040). Higher daily duration (P = 0.024) and intensity (P = 0.012) of locomotor activity were observed in BCD-treated dogs compared to baseline. No significant change was observed in either group for CSOM. Conclusions. Treatment with BCD improved the limb impairment and enhanced the locomotor activity in dogs afflicted by naturally-occurring OA. Those preclinical findings provide interesting and new information about the potential of BCD as an OA therapeutic.

A medicinal herb-based natural health product improves the condition of a canine natural osteoarthritis model: A randomized placebo-controlled trial

An oral herb-based natural health product (NHP) was evaluated in the canine natural osteoarthritis model. At baseline, the peak vertical force (PVF, primary endpoint) and case-specific outcome measure of disability (CSOM) were recorded in privately-owned dogs. Dogs (16/group) were randomized to receive NHP formulations or a negative control. The PVF was measured at week (W) 4 and W8. Daily locomotor activity was recorded using accelerometer. The CSOMs were assessed bi-weekly by the owner. The NHP-treated dogs (n = 13) had higher PVF at W4 (p = 0.020) and W8 (p <0.001) when compared to baseline. The changes at W8 were higher than control dogs (n = 14, p <0.027) and consistent with Cohens d effect size of 0.7 (95% confidence interval: 0.0-1.5). The NHP-treated dogs had higher locomotor activity at W8 (p = 0.025) when compared to baseline. No significant change was observed for the CSOM. The NHP improved the clinical signs of osteoarthritis in this model.

Blood hypercoagulability and systemic inflammation in horses with heaves

As inflammation and coagulation are intertwined processes, the efficiency of blood coagulation of heaves-affected horses and controls were compared in an observational case-control study, using thrombelastography. In experiment 1 (Exacerbation, six heaves, five controls), horses were housed indoors and fed hay. Thrombelastography, functional fibrinogen, platelet count, hematology, and antithrombin were measured. In experiment 2 (Remission, eight heaves, 11 controls), horses were housed in a low-dust environment for at least a month when thrombelastography was performed. Heaves-affected horses in exacerbation had greater maximum amplitude and higher functional fibrinogen than controls. Heaves-affected horses in clinical remission had greater maximum amplitude than controls. The hypercoagulable state and systemic inflammation of horses with heaves may be a consequence of pulmonary inflammation and may contribute to the perpetuation of airway dysfunction.