INVESTIGATION OF A POINT-OF-CARE VISCOELASTIC COAGULATION MONITOR AND ITS COMPARISON TO THROMBOELASTOGRAPHY IN CLINICALLY HEALTHY AFRICAN ELEPHANTS (LOXODONTA AFRICANA).

Elephant endotheliotropic herpesvirus (EEHV) can induce fatal hemorrhagic disease (HD) in African elephants (Loxodonta africana). Once clinical signs develop, progression is rapid, even with aggressive treatment. There is a critical need to develop point-of-care diagnostic tests to aid in identification of EEHV-HD prior to the onset of overt clinical signs. Study objectives were to investigate a novel, point-of-care viscoelastic coagulation monitor (VCM Vet), compare the results to thromboelastography (TEG), and report traditional hemostatic analytes in adult African elephants. Whole blood was collected from seven clinically healthy elephants (four females and three males, 18-47 yr) and analyzed in duplicate via VCM Vet and kaolin-activated TEG 1-3 and 30 min following collection, respectively. Separated plasma was frozen for ancillary coagulation testing. Both analyses generated quantifiable clotting reactions with variables (median [range]) describing clot formation rate (VCM Vet, clot time = 682 s [530-987 s], clot formation time = 244 s [186-744 s], Alpha = 40° [14-47°]; TEG, reaction time = 6.2 min [3.7-11.8 min], kinetic time = 1.3 min [0.9-2.6 min], Alpha = 70° [57-77°]), clot strength (VCM Vet, maximum clot formation = 34 units [20-45 units]; TEG, maximum amplitude = 75 mm [69-80 mm], shear elastic modulus strength = 14.7 Kdynes/s [11.3-19.5 Kdynes/s]), and clot lysis (VCM Vet, lysis index at 30 min = 100% [100-99%], lysis index at 45 min = 98% [95-100%]; TEG, lysis index at 30 min = 0% [0-0.4%], lysis index at 60 min = 1.4% [0-2.6%]) recorded. Additional testing (median [range]) included D-dimer concentration (33 ng/ml [28-94 ng/ml]), prothrombin time (12.4 s [12.2-13.2 s]), activated partial thromboplastin time (17.2 s [14.2-18.8 s]), and fibrinogen concentration (297 [282-383] mg/dL). Tracings generated by VCM Vet and TEG were clinically similar, and there was visual agreement and minimal difference between quantitative variables for duplicate tests. VCM Vet is a promising, user-friendly tool for use in identification and management of coagulopathies in African elephants.

Pulmonary hypertension is associated with hypocoagulability in dogs: a retrospective analysis of 66 cases (2013-2021).

OBJECTIVE: To describe coagulation profiles in dogs with echocardiographic evidence of pulmonary hypertension (PH), to compare them to coagulation profiles in dogs without echocardiographic evidence of PH, and to determine the relationship between coagulation profiles and echocardiographic probability of PH. ANIMALS: 66 dogs with PH (cases) and 86 dogs without PH (controls). METHODS: Retrospective evaluation of records between 2013 and 2021 of dogs that had both an echocardiogram and a coagulation panel performed within 7 days. Dogs that received antithrombotics within 7 days of evaluation and dogs diagnosed with congenital or acquired coagulopathy or other severe systemic disease that could lead to coagulopathy were excluded. Dogs with a low echocardiographic probability of PH were also excluded. The dogs were divided into a PH group and non-PH group based on echocardiographic results. Demographic, clinicopathologic, and traditional coagulation parameters and VCM Vet (Entegrion) parameters were compared between the 2 groups. RESULTS: Dogs with PH were significantly older (median, 11 years vs 9.5 years, P = .02) and had a significantly lower body weight (median, 7.3 kg vs 19.3 kg, P < .001) than controls. Dogs with PH also had a significantly greater percent increase in prothrombin time (PT; P = .02), partial thromboplastin time (PTT; P < .0001), and fibrinogen (P = .045); however, their antithrombin concentration was lower (P = .005) compared to controls. Eight of 65 dogs (12.3%) in the PH group and 1/86 (1.2%) dogs in the non-PH group had an elevation of PT and/or PTT greater than 50% above the reference interval (P = .005). Dogs with PH had 11.9 times (95% CI, 1.5 to 97.9; P = .02) greater odds of being hypocoagulable than dogs without PH based on PT and PTT. CLINICAL RELEVANCE: This study demonstrated an association between a moderate to high echocardiographic probability of PH and a hypocoagulable state in dogs as determined by traditional coagulation assays. It underscores the importance of monitoring the coagulation status in canine patients with PH, particularly before initiating antithrombotic medications.

Evaluation of hemostatic derangements associated with canine anaphylaxis and the relationship to syndrome severity.

OBJECTIVE: To describe hemostatic derangements associated with canine anaphylaxis and to assess for association with syndrome severity. DESIGN: Prospective observational study. SETTING: University teaching hospital. ANIMALS: Twenty-seven client-owned dogs, recruited from November 2018 to January 2022, diagnosed with anaphylaxis of varying severity were included. Study inclusion required presentation <6 hours after initiation of clinical signs, no medications or history of illness within the prior 2 weeks, lack of comorbidities expected to affect hemostasis, and lack of a disease state that could alternatively explain the clinical presentation. INTERVENTIONS: Blood samples were collected within the first hour of presentation for CBC, serum biochemistry, prothrombin time (PT), activated partial thromboplastin time (aPTT), and viscoelastic coagulation testing for use with a cartridge-based point-of-care device. MEASUREMENTS AND MAIN RESULTS: Clotting time and clot formation time were prolonged, alpha angle and maximum clot firmness were decreased, PT and aPTT were prolonged, and platelet counts were lower in severe cases compared to mild and moderate cases. There were no differences for any parameter between mild and moderate cases. The presence or absence of abdominal effusion was not associated with hemostatic status. CONCLUSIONS: Global hemostatic derangements consistent with hypocoagulability are a prominent feature of severe anaphylaxis in dogs and should be considered for routine evaluation.

Clinical Assessment of Primary Hemostasis: A Review.

Primary hemostatic disorders such as thrombocytopenia and thrombocytopathia are commonly encountered in small animal practice. The key stages of primary hemostasis include platelet adhesion, activation, and aggregation. Understanding the interaction between tissues, platelets, and signaling molecules not only helps clinicians comprehend clot formation but also better recognize thrombocytopathias. Although congenital thrombocytopathia is rare, commercially available platelet function tests allow veterinarians to narrow differentials in many clinical settings. Thrombocytopenia can be easily diagnosed in any clinical setting. In this paper, we review the current understanding of primary hemostasis in veterinary medicine, including the clinical presentation and available diagnostics to identify platelet abnormalities.

Preliminary evaluation of reference intervals for a point-of-care viscoelastic coagulation monitor (VCM Vet) in healthy adult horses.

OBJECTIVE: To evaluate a point-of-care viscoelastic coagulation monitor (VCM Vet) for use in horses by assessing variability between devices and establish reference intervals (RIs) for healthy adult horses. DESIGN: Prospective observational study. SETTING: Two university teaching hospitals. ANIMALS: Healthy adult horses (n = 68). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Blood collected by direct jugular venipuncture was applied directly from the syringe into 2 VCM Vet cassettes to establish coefficients of variation (CVs) and RIs for reported parameters of clotting time (CT), clot formation time (CFT), alpha angle, amplitude at 10 and 20 minutes, maximum clot firmness, and lysis index at 30 and 45 minutes. CVs for each parameter were within clinical tolerance. There was a significant difference in CT between institutions (P < 0.001). Differences in CV were found between institutions for CT (P = 0.003) and CFT (P = 0.01). Healthy horse RIs were calculated for the overall data set and each individual institution. Calculated RIs were as follows: CT, 255.6-1233.9 seconds; CFT, 89.4-581 seconds; alpha angle, 11.4-53.6°; maximum clot firmness, 18-37.7; lysis index at 30 minutes, 97.3%-102.1%; lysis index at 45 minutes, 80.8%-103.3%; amplitude at 10 minutes, 8.7-28.3; and amplitude at 20 minutes, 17.4-35.7. CONCLUSIONS: VCM Vet is a repeatable and practical option for rapid point-of-care assessment of hemostasis in horses but has a wide RI and is susceptible to variability. Establishment of institution-specific RIs is recommended.

Prolonged holding time and sampling protocol affects viscoelastic coagulation parameters as measured by the VCM-Vet™ using fresh equine native whole blood.

OBJECTIVES: Determine the effect of sample holding time and single sample reuse on viscoelastic coagulation parameters when using fresh equine native whole blood. ANIMALS: 8 healthy adult horses from a university teaching herd. PROCEDURES: Blood collected by direct jugular venipuncture (18 ga needle, 3 mL syringe) was held at 37 °C for 2, 4, 6, or 8 minutes according to 1 of 2 protocols. Syringes were gently inverted twice, a small amount of blood was expressed, testing cartridges were filled, and placed within the VCM-Vet™ device (Entegrion Inc). Protocol A: samples were processed from a single syringe. Protocol B: 4 syringes were drawn through a single needle. VCM-Vet™ measures assessed included clot time (CT), clot formation time (CFT), alpha angle (AA), amplitude at 10/20 minutes (A10/A20), maximal clot firmness (MCF), and lysis index at 30/45 minutes (LI30/LI45). Differences over time were examined using the Friedman test and post hoc Wilcoxon Rank Sum Test with Bonferroni correction, P ≤ .05. RESULTS: Following Protocol A, there was a significant effect of holding time for CT (P = .02), CFT (P = .04), and AA (P = .05). CT and AA decreased over time, while CFT increased. Samples handled by Protocol B showed no significant difference over time for any of the VCM-Vet™ parameters. CLINICAL RELEVANCE: Sample holding time and handling protocol impact VCM-Vet™ testing results of fresh equine native whole blood. Viscoelastic coagulation samples tested using the VCM-Vet™ may be held unagitated for up to 8 minutes after collection while warm, but should not be reused.

Use of two point-of-care analyzers provides reference intervals of prothrombin time and activated partial prothrombin time in nonanesthetized healthy ferrets (Mustela putorius furo).

OBJECTIVE: Coagulation tests are an essential tool in the diagnosis and management of coagulopathies in mammals. The aim of the current study was to establish reference intervals for prothrombin time (PT) and activated partial PT (aPTT) in healthy ferrets using 2 different point-of-care analyzers (Idexx Coag DX and MS QuickVet Coag Combo). ANIMALS: 86 clinically healthy ferrets under 3 years of age (47 females and 39 males) from 4 breeders and 2 private practices. PROCEDURES: Blood samples were collected from the cranial vena cava in all ferrets without anesthesia and placed in trisodium 3.2% citrated plastic tubes. Sixty-six blood samples from the 4 ferret breeding farms and 1 private practice were analyzed using the Idexx Coag DX and 21 from the other private practice using the MS QuickVet Coag Combo. RESULTS: Reference intervals for the Idexx Coag DX were as follows: aPTT (n = 65), 69.84 to 105.99 seconds; PT (65), 14.44 to 21.98 seconds. Reference intervals for the MS QuickVet Coag Combo were as follows: aPTT (n = 21), 74.90 to 115.50 seconds; PT (21), 18.31 to 23.05 seconds. With both types of analyzers, there was no significant age effect on aPTT and PT. CLINICAL RELEVANCE: This study provided coagulation times for 2 point-of-care analyzers in healthy ferrets as a tool for the diagnosis of coagulopathies.

Comparison of a viscoelastic point-of-care coagulation monitor with thromboelastography in sick dogs with hemostatic abnormalities.

BACKGROUND: Viscoelastic coagulation monitor (VCM-Vet) is a point-of-care device that has been used to characterize hemostatic abnormalities in sick pets but has not been validated in veterinary patients. OBJECTIVES: We aimed to compare VCM-Vet and thromboelastography (TEG) in sick dogs with suspected disorders of hemostasis. METHODS: Duplicate VCM-Vet tests using untreated native blood performed concurrently on two VCM-Vet machines, and simultaneous TEG tests were performed (one citrated native (CN), and one activated with tissue factor (TF) at a 1:3600 dilution). Each VCM-Vet result was compared with both TF-activated and CN TEG. RESULTS: Fifty-three dogs were enrolled. Eleven cases displayed apparent hyperfibrinolysis. Spearman correlation coefficients for individual VCM-Vet devices and CN and TF TEG were obtained between R and CT values and ranged from 0.21 to 0.27, CFT and K (r = 0.60-0.67), angles (r = 0.51-0.62), and MCF and MA (r = 0.85-0.87). Comparison of the two VCM-Vet devices displayed positive correlations for all clot formation parameters with Lin's concordance correlation coefficients of 0.75-0.95. Variable lysis parameter agreement existed between the VCM-Vet devices and VCM-Vet and TEG. When samples were classified as hypercoagulable or coagulopathic, VCM-Vet had a low positive predictive value (17-33%) for the detection of hypercoagulable states and a moderate negative predictive value (64-74%) for the detection of coagulopathy as defined by TEG. CONCLUSIONS: VCM-Vet and TEG had variable correlations in clot formation values and a strong correlation for final clot strength. More information is needed to make conclusions about the lysis parameters. Artifact in the fibrinolysis portion of the test can confound the interpretation of VCM-Vet results.

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.

Point-of-care global coagulation assay parameters in normal dogs and dogs with primary immune-mediated hemolytic anemia.

OBJECTIVE: To compare viscoelastic parameters between healthy control dogs and dogs with primary immune-mediated hemolytic anemia (pIMHA) using a new, point-of-care viscoelastic coagulation monitor (VCM).a DESIGN: Retrospective study from 2017 to 2021. SETTING: Three regional private referral centers. ANIMALS: Eighteen client-owned dogs with pIMHA and 33 healthy control dogs. pIMHA dogs were defined based on established criteria. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical records of dogs with pIMHA and VCM performed at diagnosis from 2017 to 2021 and apparently healthy control dogs voluntarily enrolled in the blood donor program from 2017 to 2018 were reviewed. For the healthy control dogs, consent was obtained to perform VCM in addition to traditional screening. Compared to healthy control dogs, dogs with pIMHA had mean VCM parameters consistent with hypercoagulability, demonstrated by lower mean (SD) clot formation time (108 s [30] vs 233 s [55]; P < 0.0001), higher mean alpha angle (62 degrees [6] vs 52 degrees [6]; P < 0.0001), higher mean maximum clot formation (49 VCM units [11] vs 32 VCM units [5]; P < 0.0001), higher mean amplitude at 10 minutes (40 VCM units [11] vs 19 VCM units [3]; P < 0.0001), and higher mean amplitude at 20 minutes (47 VCM units [11] vs 25 VCM units [4]; P < 0.0001). pIMHA dogs also had significantly higher median (interquartile range) lysis index at 30 minutes (100% [100-100] vs 98% [90-100]; P < 0.0001). When compared to 3 established normal canine reference intervals, dogs with pIMHA had a significantly higher proportion of VCM variables (48%-57%) consistent with hypercoagulability, and a significant percentage of pIMHA dogs (78%-89%) had VCM tracings consistent with hypercoagulability overall, irrespective of the interval utilized for interpretation. CONCLUSIONS: This study demonstrates hypercoagulability in dogs with pIMHA when compared to healthy control dogs using VCM. Prospective evaluation is warranted to further characterize these findings as well as to evaluate their clinical impact.

Kaolin activation of recalcified citrated whole blood in a point-of-care viscoelastic coagulation test.

The viscoelastic coagulation monitor (VCM) is described as a point-of-care analyzer relying on activation of fresh whole blood (FWB) via contact between 2 glass plates. Kaolin is used as an activator in thromboelastography to reduce variability and shorten clotting times. The goal of this study was to compare VCM results from kaolin-activated, recalcified citrated samples with that from FWB. The VCM testing was performed using FWB and kaolin-activated, recalcified citrated samples. The VCM results were recorded for clot time (CT; seconds), clot formation time (CFT; seconds), alpha (degree), amplitude at 10 and 20 minutes (A10 and A20; VCM units), maximum clot firmness (MCF; VCM units), and lysis index (LI; %). Values were compared using a t-test or Wilcoxon-Mann-Whitney test, with a P-value < 0.05 considered significant. Variability between samples was calculated using Levene's test. The VCM kaolin activation resulted in significantly faster CT and CFT (P < 0.0001), higher alpha angle (P < 0.001), and higher A10 and A20 (P = 0.007, P = 0.015) compared to FWB. There was no difference in MCF, LI30, or LI45. There was no difference in variability identified. The addition of kaolin to recalcified citrated whole blood VCM samples results in more rapid clotting of FWB alone and could be considered for clinical use in dogs.

Le moniteur de coagulation viscoélastique (VCM) évalue l'hémostase au point de service en utilisant du sang entier frais activé au contact de deux disques de verre. Le kaolin est un activateur utilisé en thromboélastographie pour réduire la variabilité et raccourcir le temps de coagulation.Le but de cette étude était de comparer les résultats du VCM obtenus sur des échantillons citratés recalcifiés et activés par du kaolin, avec ceux obtenus sur sang entier frais. Les échantillons sanguins ont été prélevés sur des chiens sains. Les tests avec le VCM ont été réalisés sur des échantillons de sang entier frais et sur des échantillons de sang citraté recalcifié et activé par du kaolin. Les résultats du VCM ont été enregistrés : temps de coagulation (CT; secondes), temps de formation du caillot (CFT; secondes), angle alpha (degrés), amplitude à 10 et 20 minutes (A10 et A20; unités VCM), fermeté maximale du caillot (MCF; unités VCM), index de lyse à 30 et 45 minutes après la MCF (LI; pourcentage). Les valeurs ont été comparées à l'aide d'un un test t apparié ou un test de Wilcoxon-Mann-Whitney, avec une valeur P < 0,05 considérée comme significative. La variabilité entre les échantillons a été calculée à l'aide d'un test de Levene.Les résultats du VCM réalisé sur les échantillons activés par du kaolin présentaient une diminution significative du CT et CFT (P < 0,0001) ainsi qu'une augmentation significative de l'angle alpha (P < 0,001) et de A10 et A20 (P = 0,007, P = 0,015). Aucune différence n'a été démontrée dans la MCF, l'index LI30 ou LI45. Aucune différence de variabilité n'a été identifiée.L'ajout du kaolin aux échantillons VCM de sang entier citraté recalcifié aboutit à une activation de la coagulation plus rapide que par simple contact avec les disques de verre et pourrait être envisagé pour l'usage clinique chez le chien.(Traduit par les auteurs).

Point-of-care viscoelastic coagulation assessment in healthy dogs during the perianesthetic period.

BACKGROUND: The viscoelastic coagulation monitor (VCM Vet) is a novel, portable device that provides a global assessment of hemostasis. The study aims were to evaluate serial viscoelastic analysis during the perianesthetic period in healthy dogs and to compare the agreement between two VCM Vet devices. Twenty healthy dogs undergoing orthopedic surgery were enrolled. Whole blood samples were collected from an intravenous catheter at four time points: baseline, 15 min after premedication, 60 min after inhalant initiation, and 60 min after inhalant termination. Viscoelastic tests were performed in duplicate on different devices, providing: clot time (CT; seconds), clot formation time (CFT; seconds), alpha angle (α; degrees), amplitude (units) at 10 (A10) and 20 (A20) minutes post clot time, maximum clot firmness (MCF; units), and lysis index (%) at 30 (Li30) and 45 (Li45) minutes post maximum clot formation. RESULTS: One hundred sixty samples were analyzed. The speed of CT and CFT significantly decreased an average of 25.5 s (95% confidence interval [CI]15.9-35.0) and 6.9 s (95% CI 3.1-10.7) per time point, respectively. There were no significant changes in clot strength or lysis variables. The Bland-Altman style plot shows an acceptable rate of agreement for all variables with intra-class correlation ranging from 0.64-0.94. CONCLUSION: The rate of clot formation (CT and CFT) decreased over the perianesthetic period in healthy dogs undergoing surgery. These changes were small and occurred without changes in clot strength or fibrinolysis rate, thus were not clinically relevant. There was clinically acceptable consistency between devices.

Viscoelastic Coagulation Testing in Exotic Animals.

Whole blood viscoelastic coagulation testing (VCT) allows global assessment of hemostasis and fibrinolysis. Although not widely used in exotic animal practice, VCT has been used in exotic animal research settings. Differences in patient demographics and analytical variables can result in dramatically different results with the same analyzer. To improve the utility of VCT in exotic animal medicine, standardization of protocols is necessary to facilitate the establishment of reference intervals. Despite these challenges, the quantitative/qualitative nature of VCT has already proved its real-world value to some clinicians.

Comparison of assessment of coagulation in healthy dogs by the TEG 6s and TEG 5000 viscoelastic analyzers.

The TEG 6s (Haemonetics) point-of-care viscoelastic analyzer is portable, compact, simple to use, and has the potential for rapid viscoelastic analysis that can guide the treatment of veterinary patients at the site of care. Although approved for use in people, the TEG 6s has yet to be evaluated for hemostatic analysis in veterinary medicine. Citrated whole blood (CWB) was collected from 27 healthy dogs. An aliquot of CWB from each dog was diluted by 33% with an isotonic crystalloid, representing an in vitro model of hemodilution. Unaltered and diluted CWB samples were analyzed using 2 TEG 6s and 6 TEG 5000 (Haemonetics) analyzers. The 6 TEG 5000 analyzers ran duplicate analyses of either unaltered or diluted samples using 1 of 3 reagents (Haemonetics): Kaolin TEG, RapidTEG, or TEG Functional Fibrinogen. Duplicate TEG 5000 analyses were averaged and compared with a single TEG 6s analysis. Lin concordance correlation coefficient and Bland-Altman plots were used to evaluate agreement of reaction time, kinetic time, alpha angle, maximum amplitude (MA), and G value (G) for samples activated with Kaolin TEG, and agreement of MA for samples activated with RapidTEG between the 2 machines. Overall, agreement between the TEG 6s and TEG 5000 analyzers was poor. Viscoelastic measurements by the TEG 6s and TEG 5000 in healthy dogs were not all interchangeable. Agreement was satisfactory only for MA and G measurements of diluted blood samples activated with Kaolin TEG, and MA measurements for both unaltered and diluted blood samples activated with RapidTEG.

Coagulation testing in green iguanas (Iguana iguana) with development of prothrombin time assays using reptile and avian thromboplastin.

BACKGROUND: Captive reptiles often present with clinical signs suggestive of a clotting disorder or severe illness that can induce or exacerbate a coagulopathy. However, coagulopathies in reptiles are difficult to characterize due to lack of species-appropriate reagents to perform coagulation tests. The objective of this study was to develop screening tests to evaluate the extrinsic and common pathways of coagulation in green iguanas (Iguana iguana). KEY FINDINGS: Reptile and avian thromboplastin, extracted from reptile and avian brains, respectively, were used to initiate coagulation in prothrombin time (PT) assays and commercially available reagents were used to determine Russell's viper venom time, thrombin time, and fibrinogen using the Clauss method. Coagulation assays were performed on citrate-anticoagulated plasma from 18 healthy green iguanas. Results were summarized as median (minimum-maximum): PT (reptile thromboplastin), 34.8 seconds (27.1-42.1 s), PT (avian thromboplastin), 78.5 seconds (51.6-114.23 s), Russell's viper venom time, 56.15 seconds (18.4-79.7 s), thrombin time, 10 seconds (7.0-36.5 s), and fibrinogen, 258 mg/dl (89-563.0) (2.58 [0.89-5.63 g/L]). SIGNIFICANCE: Commercial reagents can be used to evaluate the common pathway and fibrinogen; however, avian- or reptile-sourced thromboplastin is preferred for a reliable coagulation trigger to perform the PT assay and evaluate the extrinsic pathway.

In vitro effect of hydroxyethyl starch on coagulation in dogs as assessed by dynamic viscoelastic coagulometry.

OBJECTIVE: To evaluate the effect of 6% hydroxyethyl starch (HES) 670/0.75 and 6% HES 130/0.4 dilution of canine whole blood on coagulation using dynamic viscoelastic coagulometry (DVC). ANIMALS: 56 healthy adult dogs. PROCEDURES: 2 blood samples were obtained from each dog and randomized to 1 of 7 groups-undiluted or 2 dilutions (1:3 or 1:10) of 3 different fluids: saline (0.9% NaCl) solution, 6% HES 670/0.75, or 6% HES 130/0.4. Dilutions were calculated to simulate approximately a 10- or 30-mL/kg body weight IV bolus of each fluid. DVC was performed on each sample. Coagulation parameters compared between groups included clot rate (CR), platelet function (PF), and activated clotting time. RESULTS: Dilution with saline solution did not significantly affect coagulation, while dilution with HES 670/0.75 and HES 130/0.4 caused a dose-dependent significant decrease in CR (1:3 HES 670/0.75, P = 0.007; 1:10 HES 670/0.75, P = 0.002; 1:3 HES130/0.4, P < 0.0001; and 1:10 HES 130/0.4, P = 0.0003) and PF (1:3 HES 670/0.75, P < 0.0001; 1:10 HES 670/0.75, P < 0.0001; 1:3 HES130/0.4, P < 0.0001; and 1:10 HES 130/0.4, P = 0.0015). CLINICAL RELEVANCE: Dilution of canine blood with HES 670/0.75 and HES 130/0.4, at clinically relevant doses (10 and 30 mL/kg), led to significant hypocoagulability beyond dilutional effect. This was, in part, due to impaired PF, which was significantly greater with HES 670/0.75. Further research using DVC to assess the effects of HES on coagulation in dogs, ideally with clinical conditions warranting HES administration, is needed.

Response of the VCMVet viscoelastic coagulation monitor to veterinary environmental simulation challenges.

BACKGROUND: Traditional viscoelastic clotting tests are significantly impacted by the operator and environmental variation. The VCMVet coagulation monitor could provide a more user-friendly alternative for veterinary practices. OBJECTIVES: We aimed to determine if environmental vibration commonly encountered in veterinary practice alters the results of a point-of-care viscoelastic device, the VCMVet. METHODS: Nine fresh whole blood samples from healthy dogs were evaluated simultaneously using VCMVet instruments under four environmental conditions: (normal) alone and undisturbed on a raised tabletop, (centrifuge) on a countertop 6 inches from a centrifuge that operated at 12 000 rpm for 10 minutes every 20 minutes, (workspace) on a tabletop workspace in proximity to two heavy-use computers, and (gurney) on a rolling gurney at a walking pace for 10 minutes every 20 minutes. Results were compared between conditions using a Friedman test, and if this was significant (P-value < .05), it was followed by a Wilcoxon test for paired samples. RESULTS: Analysis of samples on a rolling gurney created obvious movement artifacts, and this condition was excluded from statistical analysis. The centrifuge condition resulted in a significantly higher alpha angle (median 49 degrees, interquartile range 4) than the normal condition (median 46 degrees, interquartile range 5, P = .0078). Other viscoelastic parameters were not significantly different between the normal, centrifuge, and workspace conditions. CONCLUSIONS: The VCMVet is suitable for use in a busy veterinary environment but should be protected from vibration. The instrument does not produce reliable results when operated on a moving gurney, and it should be stationary during sample analysis.

Assessment of thrombin generation in horses using a calibrated automated thrombogram.

BACKGROUND: The amount of thrombin generated reflects the endogenous thrombin potential (ETP), which depends on the balance of pro- and anticoagulant factors. The calibrated automated thrombogram (CAT) allows for the direct measurement of thrombin generation during the clotting process. OBJECTIVES: (1) To describe the results of the CAT assay in horses, (2) to establish intra-assay and intra- and interindividual variation of thrombin generation in healthy horses, and (3) to compare in vitro low-molecular-weight heparin (LMWH) sensitivity between healthy and sick horses. The hypothesis for the last objective is that inhibition of thrombin generation in sick horses requires higher heparin concentrations. METHODS: The plasma of 10 healthy mixed breed horses was used for the determination of normal thrombin generation parameters (lag time, time to peak, peak thrombin concentration, and ETP). Five of the healthy horses were compared with five horses with systemic inflammatory response syndrome (SIRS). In vitro heparin sensitivity was determined using LMWH. RESULTS: The intra-assay variation was small (<5%) for all parameters. Relatively large intra- and interindividual variation were observed in healthy horses. Four of the five sick horses with SIRS had a thrombogram compatible with a hypercoagulable state. The in vitro heparin sensitivity test suggested decreased sensitivity to LMWH in hypercoagulable states. CONCLUSIONS: The CAT assay could detect coagulopathy in horses. In vivo experiments are needed to confirm that it can be used to monitor responses to LMWH therapy.

A pilot study evaluating the Calibrated Automated Thrombogram assay and application of plasma-thromboelastography for detection of hemostatic aberrations in horses with gastrointestinal disease.

BACKGROUND: Critically ill horses, such as horses with gastrointestinal (GI) disease, often suffer from hemostatic aberrations. Global hemostatic tests examining the initiation of coagulation, clot strength and fibrinolysis, such as the Calibrated Automated Thrombogram (CAT) and plasma-thromboelastography (TEG) have not been evaluated in horses. This study aimed to evaluate CAT and apply plasma-TEG in horses. Test performance of CAT was evaluated on equine platelet poor plasma with intra- and inter-assay variability (CV) and a heparin dilution curve. To examine clinical performance of both tests, group comparisons were assessed comparing healthy horses, horses with mild and severe GI disease with both CAT and plasma-TEG. RESULTS: For CAT, intra- and inter-assay CVs were established for lag-time (1.7, 4.7%), endogenous thrombin potential (1.6, 4.6%), peak (2.6, 3.9%) and time to peak (ttPeak) (1.9, 3.4%). Increasing heparin concentrations led to the expected decrease in thrombin generation. In the group comparison analysis, CAT showed significant higher peak (p = 0.04) and ttPeak (p = 0.008) in the severe GI disease group compared to horses with mild GI disease and healthy horses, respectively. Plasma-TEG showed an increased angle (p = 0.032), maximum amplitude (p = 0.017) and shear elastic force (G) (p = 0.017) in the severe GI disease group compared to healthy horses. CONCLUSIONS: CAT performed well in horses. Both CAT and plasma-TEG identified hemostatic aberrations in horses with severe GI disease compared to healthy horses. Further studies including more horses, are needed to fully appreciate the use of CAT and plasma-TEG in this species.

Evaluation of hemostasis in hyperthyroid cats.

BACKGROUND: Hyperthyroid cats might have a predisposition to arterial thrombus formation. The mechanism for thrombogenesis currently is unknown but could be associated with systemic hypercoagulability as seen in hyperthyroid humans. OBJECTIVE: Our purpose was to evaluate markers of hemostasis in hyperthyroid cats compared to healthy cats, and in hyperthyroid cats before and after radioactive iodine treatment (RIT). ANIMALS: Twenty-five cats with hyperthyroidism and 13 healthy euthyroid cats >8 years of age. METHODS: Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, antithrombin (AT), D-dimers, thrombin-antithrombin complexes (TAT), von Willebrand Factor antigen (vWF : Ag), and activity of factors VIII and IX were measured. An echocardiogram was performed in all cats. Hemostatic markers and echocardiogram were evaluated again 6 to 9 months after successful RIT in 7 cats. RESULTS: Hyperthyroid cats had higher fibrinogen concentration (P < .0001), AT activity (P < .0001), and vWF : Ag concentration (P = .01) than healthy control cats with all results decreasing significantly post-RIT. Hyperthyroid cats were not more likely to be in a hypercoaguable state than euthyroid cats (P = .08). Serum T4 concentration was not a predictor of a hypercoagulable state (P = .53). CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperthyroid cats have evidence of altered hemostasis that does not appear to be solely attributable to cardiac abnormalities, but no evidence of a hypercoagulable state. Findings suggest altered hemostasis resolves after RIT. Hyperthyroid cats could have endothelial dysfunction as indicated by increased vWF : Ag which could potentiate thrombogenesis.