The influence of inflammation and hematocrit on clot strength in canine thromboelastographic hypercoagulability

Objective

To investigate parameters causing canine thromboelastographic hypercoagulability and to investigate whether thromboelastography (TEG) with Cytochalasin D (Cyt D) added is related to parameters of platelet activity.

Design

Prospective observational study on hemostatic and inflammatory parameters. Data were collected between November 2012 and July 2013.

Setting

University teaching hospital.

Animals

Twenty‐eight dogs suffering from diseases predisposing to thrombosis and 19 clinically healthy dogs. Diseased dogs were enrolled if they fulfilled inclusion criteria regarding age, size, informed client consent, and obtained a diagnosis of a disease that has been associated with thrombosis or hypercoagulability.

Interventions

None.

Measurements and Main Results

Parameters of coagulation and anticoagulation, fibrinolysis, and antifibrinolysis, platelet activity, inflammation, platelet count, and hematocrit were measured using CBC, TEG, platelet aggregation on multiplate, platelet activity on flow cytometry, and hemostatic and inflammatory markers on plasma and serum analyses. ANOVA and multilinear regression analyses indicated that especially hematocrit and the inflammatory parameters C‐reactive protein and interleukin‐8 showed best association with overall clot strength in diseased dogs with hypercoagulable TEG tracings. Ratios presumed to reflect platelet contribution to the TEG tracing obtained in TEG analyses with Cyt D were related especially with hematocrit and P‐selectin expression of platelets measured after γ‐Thrombin activation on flow cytometry.

Conclusion

Overall clot strength in TEG analyses of the hypercoagulable dogs included in the present study appears to be primarily associated with inflammation as well as hematocrit. Furthermore, the ratio between standard TEG analyses and TEG analyses with Cyt D may reflect some degree of platelet activity.     

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 κ 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), α‐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.     

Hemostatic abnormalities in dogs with carcinoma: a thromboelastographic characterization of hypercoagulability

Hemostatic abnormalities were investigated in 32 dogs with carcinoma and 19 age-matched healthy dogs. Thromboelastography, hemostasis profile (i.e. prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration), platelet count (PLT), thrombin-antithrombin complexes (TAT), and plasminogen activator inhibitor-1 (PAI-1) activity were evaluated. Dogs with carcinomas had faster thrombus generation (TEG(TG), a mathematic value obtained from the first derivate of the thromboelastographic tracing; 834.8±91.1 vs. 707.8±75.8mm/min; mean±SD), increased fibrinogen concentration (276 vs. 151mg/dL), and PLT (425 vs. 324U×10(9)/L), but had decreased PAI-1 activity (15.7 vs. 26.2IU/mL).The most common hemostatic abnormalities found in carcinoma dogs were hypercoagulability (TEG(TG)>mean+2 SD of healthy dogs) and thrombocytosis (PLT>424×10(9)U/L) in 46% of cases, and hyperfibrinogenemia (fibrinogen >384mg/dL) in 32% of cases. Disseminated intravascular coagulation was uncommon and the extent of disease was not correlated with hypercoagulability. TEG(TG) showed good correlation with fibrinogen (r=0.80) and hyperfibrinogenemia seems to be a main factor of the hypercoagulable state in carcinoma dogs. In conclusion, TEG(TG) is a valid parameter to diagnose hypercoagulability.     

Thromboelastographic results and hypercoagulability in dogs with surgically treated hepatocellular adenoma and carcinoma: A Veterinary Society of Surgical Oncology prospective study

Background

The most common haemostatic abnormality in dogs with cancer is hypercoagulability. A transient hypercoagulability has been documented in people with hepatocellular carcinoma (HCC) that resolves within weeks following hepatic tumour resection.

Objective

The objective was to compare the haemostatic status of dogs with liver tumours and healthy control dogs, by comparing coagulation and thromboelastography (TEG) measurements at three time points.

Methods

Liver tumour and healthy control dogs receiving surgery for liver lobectomy and ovariohysterectomy, respectively, were prospectively enrolled. All dogs had blood collected at three time points: pre-operative, 24 h post-operative and ~2 weeks post-operative. Haematological and haemostatic values were compared across time points in each group using repeated measures ANOVA tests.

Results

Ten and eight dogs were enrolled for the liver and control groups, respectively. Platelet count was significantly higher in the liver group than the control group at all time points, but within the normal range (pre-operative: 438.7 vs. 300.9 × 10⁹/L, p = .0078; 24 h post-operative: 416.2 vs. 283.9 × 10⁹/L, p = .0123; 10–14 days post-operative: 524.6 vs. 317.3 × 10⁹/L, p = .0072). The measure of the overall coagulant state (G-value) was significantly increased for the liver group compared to the control group at all time points (pre-operative: 15.6 vs. 8.6 d/sc, p = .0003; 24 h post-operative: 18.3 vs. 11.2 d/sc, p = .039; 10–14 days post-operative: 15.1 vs. 9.6 d/sc, p = .015).

Conclusion

The liver group was hypercoagulable based on elevated G-values at all time points compared to the control group. This hypercoagulability was attributed to the effect of hepatic tumours alone, and not secondary to surgery and anaesthesia.     

Evaluation of human recombinant tissue factor-activated thromboelastography in 49 dogs with neoplasia

BACKGROUND: Abnormal routine coagulation assay results have been reported to be common in veterinary patients with neoplasia, but the overall hemostatic functional state, including hypercoagulability, has not been described. HYPOTHESIS: The overall hemostatic functional state, including hypercoagulability, can be assessed in dogs with neoplasia by tissue factor (TF)-activated thromboelastography (TEG). ANIMALS: Thirty-six dogs with malignant neoplasia and 13 dogs with benign neoplasia presented to the Small Animal Veterinary Teaching Hospital, The University of Copenhagen, Frederiksberg, Denmark. METHODS: Prospective study evaluating the overall hemostatic functional state in dogs with neoplasia by a newly validated TF-activated TEG assay and routine coagulation parameters activated partial thromboplastin time (aPTT), prothrombin time (PT), platelet count, and D-dimer concentration. RESULTS: Hemostatic dysfunction was observed in 28/49 (57%) dogs with neoplasia. Twenty-four were dogs with malignant neoplasia, the majority of which 18/36 (50%) were hypercoagulable, whereas 6/36 (17%) were hypocoagulable. All hypocoagulable dogs had metastatic disease. The proportion of dogs with altered hemostasis was significantly different between dogs with malignant and benign neoplasia. CONCLUSIONS AND CLINICAL IMPORTANCE: TF-activated TEG detected hypercoagulable and hypocoagulable states in this population of dogs with neoplasia. The most common hemostatic abnormality in dogs with malignant neoplasia was hypercoagulability. These findings suggest that this novel hemostatic function test may be of value as a cage side method for the assessment of overall hemostatic function in dogs with cancer, including the detection of both hyper- and hypocoagulable states as well as mixed disorders.     

Hypercoagulability in dogs with protein-losing enteropathy

Background: Dogs with protein‐losing enteropathy (PLE) have previously been reported to present with thromboembolism; however, the prevalence and pathogenesis of hypercoagulability in dogs with PLE have not been investigated so far. Hypothesis: Dogs with PLE are hypercoagulable compared with healthy control dogs. Animals: Fifteen dogs with PLE. Thirty healthy dogs served as controls (HC). Methods: A prospective study was performed including 15 dogs with PLE. All dogs were scored using the canine chronic enteropathy activity index (CCECAI). Thromboelastography (TEG) and other measures of coagulation were evaluated. Recalcified, unactivated TEG was performed and reaction time (R), kinetic time (K), alpha angle (α), and maximum amplitude (M_A) values were recorded. Nine dogs were reassessed after initiation of immunosuppressive treatment. Results: All dogs with PLE in the study were hypercoagulable with decreased R (PLE: median 7.8, range [2.4–11.2]; HC: 14.1 [9.1–20.3]), decreased K (PLE: 2.5 [0.8–5.2]; HC: 8.25 [4.3–13.1]), increased α (PLE: 56.7 [38.5–78.3]; HC: 25.6 [17–42.4]), and increased M_A (PLE: 68.2 [54.1–76.7]; HC: 44.1, [33.5–49]) (all P < .001). Median antithrombin (AT) concentration was borderline low in PLE dogs; however, mean serum albumin concentration was severely decreased (mean 1.67 g/dL ± 5.1, reference range 2.8–3.5 g/dL). Despite a significant improvement in serum albumin and CCECAI, all 9 dogs with PLE were hypercoagulable at re‐examination. Conclusions and Clinical Importance: The hypercoagulable state in dogs with PLE cannot be solely attributed to loss of AT. Despite good clinical response to treatment, dogs remained hypercoagulable and could therefore be predisposed to thromboembolic complications.     

Serial assessment of the coagulation status of dogs with immune-mediated haemolytic anaemia using thromboelastography

This study investigated the coagulation status of dogs with immune-mediated haemolytic anaemia (IMHA) over time. Thirty animals with primary IMHA were blood sampled on three occasions over a 5 day period and assays performed included prothrombin time, activated partial thromboplastin time, D-dimer and fibrinogen concentration, antithrombin activity and recalcified unactivated thromboelastography (TEG). Based on TEG, dogs with IMHA were significantly hypercoagulable vs. controls (P<0.001) and over the 5 day period, 3/4 of the TEG parameters reflected increased clotting kinetics (P ≤ 0.02). The 30 day survival of these patients was 80% and, at hospital admission, the TEG maximum amplitude (MA) was significantly higher in survivors than non-survivors (P=0.015). Each unit increase in MA was associated with an increased odds of 30 day survival of 1.13 (95%; CI 1.02-1.25). Based on TEG, most dogs with IMHA were hypercoagulable on admission and their clotting kinetics increased with time. Relative hypocoagulability identified by TEG at initial assessment was found to be a negative prognostic indicator.     

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.     

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.     

Evidence of hypercoagulability in dogs with parvoviral enteritis

OBJECTIVE: To determine whether dogs with naturally occurring canine parvoviral (CPV) enteritis have laboratory evidence of hypercoagulability. DESIGN: Case-control study. Animals-9 dogs with naturally occurring CPV enteritis and 9 age-matched control dogs. PROCEDURE: Blood was collected from all dogs within 24 hours of admission for thromboelastography (TEG) and determination of activated partial thromboplastin time (aP-TT), prothrombin time (PT), antithrombin III (AT) activity, and fibrinogen concentration. Fibrin-fibrinogen degradation product (FDP) concentration, D-dimer concentration, and platelet count were obtained in dogs with CPV enteritis only. Records were reviewed for evidence of thrombosis or phlebitis. RESULTS: All 9 dogs with CPV enteritis had evidence of hypercoagulability, determined on the basis of significantly increased TEG maximum amplitude and decreased AT activity. Fibrinogen concentration was significantly higher in dogs with CPV enteritis than in control dogs. The aPTT was moderately prolonged in dogs with CPV enteritis, and FDP concentration was < 5 mg/ml in 7 of 9 dogs. No dogs had a measurable D-dimer concentration. Platelet counts were within reference range. Four of 9 dogs had clinical evidence of venous thrombosis or phlebitis associated with catheters. One dog had multifocal splenic thrombosis identified at necropsy. CONCLUSIONS AND CLINICAL RELEVANCE: Dogs with CPV enteritis have a high prevalence of clinical thrombosis or phlebitis and laboratory evidence of hypercoagulability without disseminated intravascular coagulopathy. Thromboelastography may help identify hypercoagulable states in dogs.     

Hypercoagulability in Dogs with Blastomycosis

Background

Blastomycosis is a potentially fatal fungal disease that most commonly affects humans and dogs. The organism causes systemic inflammation and has a predilection for the lungs. The inflammation might lead to a hypercoagulable state with microemboli in the pulmonary circulation which could contribute to inadequate oxygen exchange in infected dogs.

Hypothesis/Objectives

Dogs with blastomycosis will be hypercoagulable compared with healthy case‐matched controls.

Animals

Client‐owned dogs with a diagnosis of blastomycosis (n = 23) and healthy case‐matched controls (n = 23).

Methods

Prospective case‐controlled study of client‐owned dogs presented to a veterinary teaching hospital with clinical signs compatible with blastomycosis. Complete blood counts, fibrinogen, PT, aPTT, thromboelastometry (TE), thrombin antithrombin complexes (TAT), and thrombin generation were evaluated.

Results

Cases had a leukocytosis compared with controls [mean (SD) 16.6 (7.6) × 10³/μL versus 8.2 (1.8) × 10³/μL, P < .001], hyperfibrinogenemia [median 784 mg/dL, range 329–1,443 versus median 178 mg/dL, range 82–257, P < .001], and increased TAT concentrations [mean (SD) 9.0 (5.7) μg/L versus 2.0 (2.8) μg/L, P < .001]. As compared to controls, cases were also hypercoagulable as evaluated by thromboelastometry and had increased in vitro thrombin generation on calibrated automated thrombography.

Conclusions and Clinical Importance

Hypercoagulability occurs in dogs with systemic blastomycosis. Additional studies are needed to explore a possible contribution of thrombogenicity to the clinical manifestations of systemic blastomycosis.     

Associations among systemic blood pressure,microalbuminuria and albuminuria in dogs affected with pituitary- and adrenal-dependent hyperadrenocorticism

Background

Hypertension and proteinuria are medical complications associated with the multisystemic effects of long-term hypercortisolism in dogs with hyperadrenocorticism (HAC).

Methods

This study investigated the relationships among adrenocorticotropic hormone (ACTH)-stimulation test results, systemic blood pressure, and microalbuminuria in clinically-healthy dogs (n = 100), in dogs affected with naturally occurring pituitary-dependent (PDH; n = 40), or adrenal-dependent hyperadrenocorticism (ADH; n = 30).

Results

Mean systemic blood pressure was similar between clinically healthy dogs and dogs with HAC (p = 0.803). However the incidence of hypertension was highest in dogs with ADH (p = 0.017), followed by dogs with PDH, with the lowest levels in clinically healthy dogs (p = 0.019). Presence of microalbuminuria and albuminuria in clinically healthy dogs and dogs affected with HAC was significantly different (p < 0.001); incidences of albuminuria followed the same pattern of hypertension; highest incidence in dogs with ADH, and lowest level in clinically healthy dogs; but microalbuminuria showed a different pattern: clinically healthy dogs had highest incidences and dogs with ADH had lowest incidence. The presence of albuminuria was not associated with blood pressure values, regardless of whether dogs were clinically healthy or affected with ADH or PDH (p = 0.306).

Conclusions

Higher incidence of hypertension and albuminuria, not microalbuminuria was seen in dogs affected with HAC compared to clinically healthy dogs; incidence of hypertension and albuminuria was significantly higher in dogs affected with ADH compared to PDH. However, presence of albuminuria was not correlated with systemic blood pressure.     

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.     

Exercise induced hypercoagulability,increased von Willebrand factor and decreased thyroid hormone concentrations in sled dogs

Background

Sled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases. In addition, these dogs also become hypothyroid during training and exercise. Canine hypothyroidism has been shown to correlate with decreased von Willebrand factor antigen and potentially increased bleeding tendency. Whether increased gastro intestinal bleeding risk is exacerbated due to changes in the hemostatic balance is unknown. The aim of this study was to investigate the hemostatic balance in sled dogs before and after exercise and in addition evaluate any correlation to thyroid status. Twenty sled dogs have been assessed in untrained and trained condition and immediately after exercise. The first sample was collected in the autumn following a resting period, and subsequently the dogs were exposed to increased intensity of training. After four months the peak of physical condition was reached and a 68 km long sled pulling exercise was performed. Samples were collected before and immediately after the exercise. Evaluated parameters were: plasma thromboelastographic (TEG) R, SP, α and MA, activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, von Willebrand factor (vWf), D-dimer, platelet number, thyroid hormones, hematocrit and C-reactive protein (CRP).

Results

Exercise induced an overall hypercoagulable state characterized by significant decreases of TEG R and SP and an increase of α, increased concentrations of plasma vWf and decreased aPTT. In addition, a proinflammatory status was seen by a significant increase of serum CRP concentrations. Thyroid status was confirmed to be hypothyroid as training and exercise induced significant decrease of thyroxin (T4), free thyroxin (fT4) and thyroxin stimulating hormone (TSH) concentrations. Fibrinogen decreased significantly and PT increased. The training-induced changes showed correlation between T4, fT4 and aPTT and correlation between TSH and fibrinogen. Exercise-induced changes showed correlation between T4 and PT.

Conclusions

Exercise was associated with a hypercoagulable state and an increase of vWf concentration in this group of sled dogs. Decreased thyroid hormone concentrations after training and exercise were confirmed, but were associated with increased and not decreased vWf in this group of sled dogs.     

Thromboelastography results on citrated whole blood from clinically healthy cats depend on modes of activation

Background

During the last decade, thromboelastography (TEG) has gained increasing acceptance as a diagnostic test in veterinary medicine for evaluation of haemostasis in dogs, however the use of TEG in cats has to date only been described in one previous study and a few abstracts. The objective of the present study was to evaluate and compare three different TEG assays in healthy cats, in order to establish which assay may be best suited for TEG analyses in cats.

Methods

90 TEG analyses were performed on citrated whole blood samples from 15 clinically healthy cats using assays without activator (native) or with human recombinant tissue factor (TF) or kaolin as activators. Results for reaction time (R), clotting time (K), angle (α), maximum amplitude (MA) and clot lysis (LY30; LY60) were recorded.

Results

Coefficients of variation (CVs) were highest in the native assay and comparable in TF and kaolin activated assays. Significant differences were observed between native and kaolin assays for all measured parameters, between kaolin and TF for all measured parameters except LY60 and between native and TF assays for R and K.

Conclusion

The results indicate that TEG is a reproducible method for evaluation of haemostasis in clinically healthy cats. However, the three assays cannot be used interchangeably and the kaolin- and TF activated assays have the lowest analytical variation indicating that using an activator may be superior for performing TEG in cats.     

Resident forum abstractsEVALUATION OF THROMBOELASTOGRAPHY (TEG) IN NORMAL CATS

Objective: To establish normal parameters of thromboelastography (TEG) in healthy adult cats. Background: Thromboelastography (TEG) is an in vitro test of coagulation that has been shown to be useful in humans, dogs and select species to identify and quantify alterations of hemostasis (e.g., hypercoagulable and hypocoagulable states). It has also been demonstrated to be useful in monitoring effects of anticoagulant therapies. This test has not been evaluated in cats. Methods: Blood was collected from 25 clinically normal cats by venipuncture using a 21 gauge×3 1/2 inch butterfly catheter and syringe for medial saphenous or jugular venipuncture. A single 1.8 mL sample in 3.8% Sodium Citrate (9:1) was collected from each cat. Recalcified whole blood was analyzed 30 minutes following collection with the TEG® 5000 analyzer (Haemoscope, Niles, IL). Analysis temperature was 37.6°C. TEG parameters recorded included: R‐value (represents initial fibrin formation), K (time from R to standard fixed measure of clot firmness which represents contributions of platelets and fibrinogen), maximum amplitude (MA; represents absolute clot strength), and alpha angle (α; the slope of TEG tracing which represents rate of clot formation). The coagulation index (CI) was derived from the formula generated for humans to provide an overall assessment of whether the sample was hyper‐ or hypocoagulable. Results: Values for the 25 normal cat samples are reported as mean ±2 standard deviations. R=2.97; 1.23–4.72; K=1.54, 0.38–2.71; α=70.70, 57.76–83.65; MA=58.50, 45.26–71.74 and CI=2.27, 0.07–4.46. Compared to historical information obtained on normal dogs, cats have significantly shorter R and K and larger α, MA and CI. Conclusions: TEG does have reproducible performance when used to evaluate coagulation status in normal cats. Compared to dogs, normal cats favor a hypercoagulable state. Species‐specific normal values are necessary for interpretation of TEG results. This test bears potential value for use in future experimental and clinical work to investigate hemostasis in cats receiving anticoagulant therapies or in cats suffering from diseases such as cardiomyopathy which are thought to be associated with altered coagulation status.     

Thromboelastography in healthy, sick non-septic and septic neonatal foals

Objectives To evaluate citrated recalcified thromboelastography (TEG) in healthy newborn foals, and to determine intra‐assay, inter‐individual and intra‐individual (at 12 h, 24 h and 7 days after birth) variations. Additionally, to compare TEG variables, haematological values and conventional coagulation profiles from healthy, sick non‐septic, and septic foals. Design Prospective study. Methods The study group comprised 18 healthy, 15 sick non‐septic and 17 septic foals. Two citrated (3.2%; 1 : 9 anticoagulant : blood ratio) blood samples were submitted for haemostatic evaluation using a TEG analyser and conventional coagulation profile. TEG values (R time (R), K time (K), angle (α), maximum amplitude (MA) and G value (G)), complete blood count (CBC) and conventional coagulation profile (prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration (Fib) and antithrombin (AT)) were evaluated. Signalment, presenting complaint, sepsis scores, blood culture results and outcome were taken from the medical records of the sick foals. Results Mean values ± SD for TEG variables in healthy neonatal foals were: R = 11.82 ± 5.35 min, K = 3.06 ± 1.34 min, α= 51.19 ± 12.66 degrees, MA = 55.06 ± 6.67 mm and G = 6361 ± 1700 dyn/cm². Mean coefficients of variation for intra‐assay/inter‐individual/intra‐individual in healthy foals were: R = 3.5/45.2/43.1%; K = 5.3/58.7/28.7%; α= 1.5/24.7/11.9%; MA = 0.3/12.1/6.1%; G = 1.6/26.7/14.7%. Septic foals had significantly greater α, MA and G values than sick non‐septic foals, and significantly greater MA and G than healthy foals, changes that are consistent with hypercoagulability. Weak correlations were detected between TEG variables and haematological or haemostatic values. Conclusions TEG could be used to provide additional information about the haemostatic system in equine neonates.     

Application of thrombelastography/thromboelastometry to veterinary medicine

Thrombelastograph analyzers are point-of-care hemostatic analyzers that provide global assessment of the hemostatic process. Thrombelastography (TEG) detects and provides a continuous recording of the changes in the viscoelastic properties of whole blood from initial clot formation through fibinolysis. TEG has been validated for use in dogs, horses, and cats. Hemostasis research using TEG has focused on test validation, alterations of TEG tracings in animals with naturally occurring diseases, and the use of TEG for monitoring various therapeutic modalities. This article reviews TEG methodology and terminology, including potential sources of preanalytical and analytical errors, the correlation between TEG and other routine hemostatic assays, and current clinical applications of TEG, with emphasis on veterinary medical practice. Data suggest that TEG may be a sensitive and useful adjunctive tool for evaluating an animal with an underlying coagulopathy, including hypercoagulability and hypocoagulability. Additional prospective studies are needed to (1) correlate TEG tracing patterns with a clinical predisposition for bleeding or thrombosis in various disease states and (2) determine whether monitoring and treating hemostatic disorders based on TEG tracings improve clinical outcome.     

Thromboelastography: a tool for measuring hypercoagulability, hypocoagulability, and fibrinolysis

Objective: To describe the technique of thromboelastography (TEG) and review the applications of this coagulation test in humans and small animals. Data sources: Data sources included scientific reviews and original research publications. Human data synthesis: TEG in humans has been used for documentation of hypercoagulable and hypocoagulable states and has been shown to be beneficial in patient management. Veterinary data synthesis: Clinical evaluation of TEG in veterinary medicine is limited; however, recent reports have documented evidence of hypercoagulability in dogs with parvovirus and protein‐losing nephropathy. Additionally, many of the research models may be relevant to veterinary patients. Conclusions: TEG provides information about coagulation that is not available through routine coagulation tests. The application of TEG monitoring to veterinary patients shows promise; however, prospective clinical studies are needed.     

Examination of hemostatic parameters to detect hypercoagulability in dogs with severe protein‐losing nephropathy

Objective – To identify hemostatic abnormalities in dogs with protein‐losing nephropathies (PLN) that represent risk factors for pathologic thrombosis. Design – Cross‐sectional observational study of client‐owned dogs with PLN, nonprotein losing renal failure (RF), and systemic illness (SI) exclusive of primary renal disease. Setting – Urban University Referral Center. Animals – A total of 29 dogs (n=11 PLN, n=7 RF, n=11 SI) were enrolled between January 2001 and July 2002. Samples were also collected from 20 clinically normal dogs to serve as hemostasis assay controls. Interventions – None. Hemostasis Testing – Citrate anticoagulated blood was collected for point‐of‐care testing with a viscoelastic monitor (thromboelastograph [TEG]) and citrate plasma was prepared for coagulation screening tests and specific assay of the following hemostatic proteins: antiplasmin, antithrombin, D‐dimer, Factor VIII, fibrinogen, plasminogen, protein C, and von Willebrand factor. Results – Dogs with PLN and RF demonstrated TEG abnormalities consistent with hypercoagulability (eg, short clotting time, high clot amplitude) and both groups had significantly lower antithrombin than the SI group. The PLN dogs had significantly higher protein C than either the RF or SI group. Hyperfibrinogenemia was a consistent finding among all 3 disease groups, and the coagulation index a measure of hypercoagulability derived from TEG parameters, directly correlated with fibrinogen values of all study dogs. Conclusions – Hemostatic abnormalities consistent with systemic hypercoagulability are common in dogs with RF and PLN, however, no prothrombotic factors unique to PLN were identified in our study. The thrombotic tendency of PLN may therefore involve parameters we did not directly assess such as platelet reactivity, fibrinolysis, perturbations in blood flow, and/or endothelial dysfunction. High protein C is a novel finding in PLN dogs of unknown clinical relevance.